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Three crystallization methods for growing large high-quality protein crystals, i.e. crystallization in the presence of a semi-solid agarose gel, top-seeded solution growth (TSSG) and a large-scale hanging-drop method, have previously been presented. In this study the effectiveness of crystallization in the presence of a semi-solid agarose gel has been further evaluated by crystallizing additional proteins in the presence of 2.0% (w/v) agarose gel, resulting in complete gelification with high mechanical strength. In TSSG the seed crystals are hung by a seed holder protruding from the top of the growth vessel to prevent polycrystallization. In the large-scale hanging-drop method, a cut pipette tip was used to maintain large-scale droplets consisting of protein-precipitant solution. Here a novel crystallization method that combines TSSG and the large-scale hanging-drop method is reported. A large and single crystal of lysozyme was obtained by this method. | The attenuation of sedimentation and convection in microgravity can sometimes decrease irregularities formed during macromolecular crystal growth. Current terrestrial protein crystal growth (PCG) capabilities are very different than those used during the Shuttle era and that are currently on the International Space Station (ISS). The focus of this experiment was to demonstrate the use of a commercial off-the-shelf, high throughput, PCG method in microgravity. Using Protein BioSolutions’ microfluidic Plug Maker™/CrystalCard™ system, we tested the ability to grow crystals of the regulator of glucose metabolism and adipogenesis: peroxisome proliferator-activated receptor gamma (apo-hPPAR-γ LBD), as well as several PCG standards. Overall, we sent 25 CrystalCards™ to the ISS, containing ~10,000 individual microgravity PCG experiments in a 3U NanoRacks NanoLab (1U = 103 cm.). After 70 days on the ISS, our samples were returned with 16 of 25 (64%) microgravity cards having crystals, compared to 12 of 25 (48%) of the ground controls. Encouragingly, there were more apo-hPPAR-γ LBD crystals in the microgravity PCG cards than the 1g controls. These positive results hope to introduce the use of the PCG standard of low sample volume and large experimental density to the microgravity environment and provide new opportunities for macromolecular samples that may crystallize poorly in standard laboratories. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,200 |
The law of Arrhenius which correlates the viscosity of a colloidal solution logarithmically to the volume percent concentration of solid matter has previously been tested only for dilute suspensions which appeared to the investigators to behave like true Newtonians. Similar suspensions have been tested at higher concentrations of solid matter and the authors found that although Arrhenius' law could not be checked, a similar exponential law evolved, which, however, is correct only within the tested region of viscosity. The authors realized that with the increase of solid matter the suspension can become plastic or pseudo‐plastic and may also show thixotropic behavior. Therefore it was considered as a major part of this investigation to determine the validity of Arrhenius' law in that region of concentration, where plasticity occurs. Although Arrhenius' law was not found to be applicable for plastic materials, two exponential laws, similar to Arrhenius' law, have been established between the plastic viscosi... | For proteins, the mechanical properties of the folded state are directly related to function, which generally entails conformational motion. Through sub-Angstrom resolution measurements of the AC mechanical susceptibility of a globular protein we describe a new fundamental materials property of the folded state. For increasing amplitude of the forcing, there is a reversible transition from elastic to viscoelastic response. At fixed frequency, the amplitude of the deformation is piecewise linear in the force, with different slopes in the elastic and viscoelastic regimes. Effectively, the protein softens beyond a yield point defined by this transition. We propose that ligand induced conformational changes generally operate in this viscoelastic regime, and that this is a universal property of the folded state. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 26,201 |
Antimicrobial peptides (AMPs) are promising candidates for new antibiotic classes but often display an unacceptably high toxicity towards human cells. A naturally produced C-terminal fragment of PGLa, named PGLa-H, has been reported to have a very low haemolytic activity while maintaining a moderate antibacterial activity. A sequential tandem repeat of this fragment, diPGLa-H, was designed, as well as an analogue with a Val to Gly substitution at a key position. These peptides showed markedly improved in vitro bacteriostatic and bactericidal activity against both reference strains and multidrug resistant clinical isolates of Gram-negative and Gram-positive pathogens, with generally low toxicity for human cells as assessed by haemolysis, cell viability, and DNA damage assays. The glycine substitution analogue, kiadin, had a slightly better antibacterial activity and reduced haemolytic activity, which may correlate with an increased flexibility of its helical structure, as deduced using molecular dynamics simulations. These peptides may serve as useful lead compounds for developing anti-infective agents against resistant Gram-negative and Gram-positive species. | Successive parameterizations of the GROMOS force field have been used successfully to simulate biomolecular systems over a long period of time. The continuing expansion of computational power with time makes it possible to compute ever more properties for an increasing variety of molecular systems with greater precision. This has led to recurrent parameterizations of the GROMOS force field all aimed at achieving better agreement with experimental data. Here we report the results of the latest, extensive reparameterization of the GROMOS force field. In contrast to the parameterization of other biomolecular force fields, this parameterization of the GROMOS force field is based primarily on reproducing the free enthalpies of hydration and apolar solvation for a range of compounds. This approach was chosen because the relative free enthalpy of solvation between polar and apolar environments is a key property in many biomolecular processes of interest, such as protein folding, biomolecular association, membrane formation, and transport over membranes. The newest parameter sets, 53A5 and 53A6, were optimized by first fitting to reproduce the thermodynamic properties of pure liquids of a range of small polar molecules and the solvation free enthalpies of amino acid analogs in cyclohexane (53A5). The partial charges were then adjusted to reproduce the hydration free enthalpies in water (53A6). Both parameter sets are fully documented, and the differences between these and previous parameter sets are discussed. (C) 2004 Wiley Periodicals, Inc. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,202 |
::: Urinary tract infections are a common disease in humans. Therefore, new methods are needed to destroy biofilms that are formed by uropathogens. Iturin A lipopeptides (LPs) C14 and C15 are potent biosurfactants synthetized by the Bacillus subtilis I′1a strain. The biological activity of extracted LPs was confirmed by examining extracts from I′1a cultures against uropathogenic bacteria that had been isolated from biofilms on urinary catheters. Compared with cultures of DSM 3257, which produce surfactin at a relatively low level, the extract obtained from strain I′1a exhibited a greater inhibitory effect against both planktonic and sessile forms of Escherichia coli, Serratia marcescens, Enterobacter cloacae, Proteus mirabilis, Citrobacter freundii and Enterococcus faecalis. Moreover, cyclic LP biosurfactants may disturb the integrity of cytoplasmic membranes; therefore, we investigated the effects of synthetized LPs on fatty acids and phospholipids of B. subtilis. LPs and lipids were analyzed using GC–MS, LC–MS/MS and MALDI-TOF/TOF techniques. Compared with B. subtilis DSM 3257, membranes of the I′1a strain were characterized by an increased amount of anteiso fatty acids and a ten-fold higher ratio of phosphatidylglycerol (PG)-to-phosphatidylethanolamine (PE). Interestingly, in cultures of B. subtilis DSM 3257 supplemented with LP extracts of the I′1a strain, the PG-to-PE ratio was fourfold higher, and the amount of anteiso fatty acids was also increased. | The present study focused on the evaluation of a nonspecific synergistic effect of biogenic silver nanoparticles (AgNPs) in combination with biosurfactants against environmental bacteria and fungi. The AgNPs were synthesized in the culture supernatants of the biosurfactant producer Bacillus subtilis grown in brewery effluent, molasses or Luria-Bertani media. Antibacterial activities were tested against Gram-positive and Gram-negative bacteria, while the antifungal activity was tested against phytopathogens. The interactions between biogenic AgNPs and DNA were investigated using a cryo-TEM technique. The presence of biosurfactant significantly increased the stability of biogenic AgNPs and enhanced their antimicrobial activities. The physical properties and antimicrobial activity of biogenic AgNPs were compared with chemically synthesized Ag nanoparticles. Biogenic silver nanoparticles showed a broad spectrum of activity against bacteria and fungi. They were most active against phytopathogenic fungi and Gram-positive bacteria and less active against Gram-negative bacteria. The nonspecific synergistic effect of biogenic AgNPs and biosurfactant on the phytopathogenic fungi was especially observed. In this report, the new roles of biosurfactants as a biogenic AgNPs stabilizer and enhancer of their antimicrobial properties are presented. Our results revealed that the biologically synthesized AgNPs by the biosurfactant-producing bacterium Bacillus subtilis grown on agro-industrial wastes, such as molasses and brewery effluent, could be used as a promising new nanoagent against microbes. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,203 |
Cohesive strength is an important parameter for understanding and modeling the mechanics of biomass detachment from bacterial biofilms. It is challenging to measure the mechanical properties of biofilms, however, because biofilms may desiccate when removed from liquid medium and they are inherently fragile. Poppele and Hozalski (Poppele and Hozalski, 2003, J Microb Methods 55:607-615) presented a microcantilever method for measuring the tensile strength of detached biofilm fragments while submersed in liquid medium. Here we present a modification of the microcantilever method to quantify the strength of intact bacterial biofilms. Initial testing was performed on Pseudomonas aeruginosa biofilms and on Staphylococcus epidermidis biofilms grown in rotating disk reactors. The cohesive strength values were highly variable (i.e., coefficients of variation ranging from 71% to 143%) and ranged from 59 to 18,900 Pa for the P. aeruginosa biofilms and from 61 to 5,840 Pa for the S. epidermidis biofilms. The biofilms also appeared to be isotropic as strength did not vary with angle of testing relative to the direction of applied shear. Strength testing using both the intact and fragment methods was performed on five samples of P. aeruginosa biofilms, and the strength populations were not from the same distribution in three cases. Equivalent diameters for the fragments detached from biofilms during strength testing ranged from 5 to 500 microm, which is within the range of size of biofilm fragments observed in the effluents of lab-scale and full-scale bioreactors. The microcantilever is a simple yet powerful tool for measuring the cohesive strength of intact biofilms at a relevant scale. | Sediment grains in rivers are often bound together and stabilized by bacterial films. Experiments and mathematical models show that sediments bound by biofilms behave like a single elastic membrane that can rip catastrophically if the river flows fast enough. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,204 |
The giant unicellular green alga Acetabularia was labeled with the lipophilic fluorochrome DiOC6 (3,3'-dihexyloxacarbocyanine) and examined by confocal laser scanning microscopy to study the distribution of the endoplasmic reticulum (ER) and its dynamic changes after the application of inhibitors. In control cells, a two-dimensional polygonal network of ER sheets and tubulus is suspended between parallel, longitudinally oriented bands. These bands coincide with the main physical tracks of organelle transport. All treatments that inhibited organelle motility caused a transformation of the polygonal network into confluent large patches of lamellar ER sheets. The shape of the lamellar sheets and residual activities of the ER were dependent on the inhibitors used. The largest ER lamellae were obtained after cytochalasin D (CD) treatment which effectively stopped cytoplasmic streaming. CD also caused the formation of a network of fine tubules overlapping with the lamellar sheets. Okadaic acid, a specific inhibitor of serine/threonine-protein phosphatases, also caused inhibition of organelle movement and enlargement of lamellar areas. Tension in the cytoplasm appeared to be reduced, as judged from the convexly curved lamellar rims and wavy connecting ER tubules. In contrast, N-ethylmaleimide, a sulfhydryl group blocking reagent, rapidly stopped streaming and halted all activities of the ER in a rigor-like state. These effects are interpreted in the context of actin-based motility phenomena prevalent in Acetabularia, and regulatory principles are discussed that might underlie ER dynamics. | Colonies of a wild strain from Lake Burley-Griffin, Australia, of the hydrocarbon-producing green alga Botryococcus were examined by confocal laser scanning microscopy. The microscope was fitted with a dual wavelength krypton-argon laser, which permitted simultaneous detection of chlorophyll autofluorescence and lipophilic dye fluorescence. This quick and simple technique revealed the precise structural conformation of the autofluorescing plastids in living cells and their 3-dimensional spatial arrangement within the dense globular colonies. Cells stained with the lipophilic carbocyanine dye, DIOC6(3) contain an apical array of intensely staining granules as well as a more diffuse internal cisternal system thought to be endoplasmic reticulum. The cationic lipophilic dye rhodamine123 revealed a finer reticulate system in the outermost cytoplasm partially overlaying the plastid. Both dyes revealed the lipophilic nature of the extracellular matrix and enabled the secretion of lipid globules exuded from the colonies to be visualized. It is suggested that confocal laser scanning microcopy would make an ideal tool to screen isolates for their potential to form and secrete hydrocarbon, processes which are still far from clearly understood in this potentially commercially important alga. | Sandwich panels with lattice cores have attracted significant interest as multifunctional structures. The lattices consist of 3D repeating unit cells constructed from plates or trusses oriented to efficiently support applied stresses. These systems show promise for supporting structural loads and mitigating the blast effects of explosions. Here, a preliminary study has been conducted to investigate the ballistic behavior of a model lattice and to explore the effect of filling the lattices void spaces with polymers and ceramics. A sheet folding and brazing method has been used to fabricate pyramidal lattice truss structures from 304 stainless steel. The impact response of the various panels was assessed after impact by spherical, 12 mm diameter, 6.9 g projectiles with an incident, zero obliquity velocity of ∼600 m/s. Empty lattice sandwich panels with an areal density of 27.7 kg m−2 do not prevent the perforation of the sandwich panel. The impact with proximal face sheet reduced the projectile velocity to ∼450 m/s (by about 25%). Interactions with the lattice trusses and the distal face sheet further slowed the projectile resulting in an exit velocity at the distal face sheet of ∼360 m/s. The projectiles energy was dissipated by face sheet plastic dishing and fracture by petaling, and by truss plastic deformation. Infiltration of the lattice with polyurethane elastomers further reduced the projectile exit velocity. The strength of the effect depended upon the modulus of the polymer (and therefore its glass transition temperature, Tg). Only high modulus (high Tg) elastomers fully arrested the projectile. The energy of the projectile in this case was dissipated by a combination of face sheet stretching and polymer deformation and fracture. Low modulus elastomers reduced the projectile exit velocity by about 45% (to ∼250 m/s) and also resulted in resealing of the projectile path within the sandwich panel core. The incorporation of ballistic fabric within the polymer infiltrated systems had little effect on the ballistic resistance. A hybrid sample containing metal encased Al2O3 prism inserts provided the greatest resistance to penetration. In this case the projectiles were arrested within a sphere diameter of the sample front surface. Several of these hybrid systems offer promise as multifunctional, ballistic resistant, load-bearing structures. | eng_Latn | 26,205 |
Two series of hybrid polyimide (PI)/multiwalled carbon nanotube (MWCNT) nanocomposites were prepared including COOH-functionalized or pristine nanotubes, and their structure, morphology and dynamics/mechanical properties at 20°C–500°C were studied using WAXD (Wide-angle X-ray diffraction), AFM (Atomic force microscopy), TEM (transmission electron microscopy), DSC (Differential scanning calorimetry), DMA (Dynamic mechanical analysis), CRS (creep rate spectroscopy) techniques, and stress–strain testing. The impact of nanofiller loadings of 0.125, 0.25, 0.5, or 1 wt% relative to PI was evaluated. Specific changes in the matrix morphology and different quality of nanotube dispersion in the nanocomposites with amorphous and semicrystalline matrices were determined. The best nanotube dispersion was observed in the composites with 0.5 wt% MWCNT-COOH. A peculiar high temperature dynamics, different for amorphous, and semicrystalline matrices, was revealed in these nanocomposites. The most dramatic changes in high... | Carbonization of the polyimide-based composite films containing carbon nanoparticles, namely nanofibers and nanocones/disks, in the temperature range 500–550°C was studied and the kinetics of the initial stage of carbonization and the effect of the filler on the mechanical properties of the carbonized films were evaluated. Two polyimides (PIs) characterized by different macrochains’ rigidity and different degrees of ordering of the intermolecular structure were used. The character of the nanofiller’s action on the kinetics of the carbonization process depends on the heating rate. In this work, the intensity of the destruction of the PI matrix of the composite films was shown to be slightly higher than that of films of the same polymers with no filler. The introduction of the carbon nanoparticles into both PIs provokes the increase in the ultimate deformation values of the partially carbonized films, while the carbonization of the unfilled PI films yields the brittle materials. The Young’s modulus ... | ABSTRACTUNC-45A is an ubiquitously expressed protein highly conserved throughout evolution. Most of what we currently know about UNC-45A pertains to its role as a regulator of the actomyosin system... | eng_Latn | 26,206 |
In this paper, we study the mechanical behaviour of multicellular aggregates using the notion of multiple natural configurations. In particular, we extend the elasto-visco-plastic model proposed in Preziosi et al. (2010, An elasto-visco-plastic model of cell aggregates. J. Theor. Biol., 262, 35-47) taking into account the liquid constituent present in cellular spheroids. Aggregates are treated as porous materials, composed of cells and filled with water. The cellular constituent is responsible for the elastic and the plastic behaviour of the material. The plastic component is due to the rearrangement of adhesion bonds between cells and it is translated into the existence of a yield stress in the macroscopic constitutive equation. On the other hand, the liquid constituent is responsible for the viscous-like response during deformation. The general framework is then applied to describe uniaxial homogeneous compression both when a constant load is applied and when a fixed deformation is imposed and subsequently released. We compare the results of the model with the dynamics observed during the experiments in Forgacs et al. (1998, Viscoelastic properties of living embryonic tissues: a quantitative study. Biophys. J., 74, 2227-2234). | A number of properties of certain living embryonic tissues can be explained by considering them as liquids. Tissue fragments left in a shaker bath round up to form spherical aggregates, as do liquid drops. When cells comprising two distinct embryonic tissues are mixed, typically a nucleation-like process takes place, and one tissue sorts out from the other. The equilibrium configurations at the end of such sorting out phenomena have been interpreted in terms of tissue surface tensions arising from the adhesive interactions between individual cells. In the present study we go beyond these equilibrium properties and study the viscoelastic behavior of a number of living embryonic tissues. Using a specifically designed apparatus, spherical cell aggregates are mechanically compressed and their viscoelastic response is followed. A generalized Kelvin model of viscoelasticity accurately describes the measured relaxation curves for each of the four tissues studied. Quantitative results are obtained for the characteristic relaxation times and elastic and viscous parameters. Our analysis demonstrates that the cell aggregates studied here, when subjected to mechanical deformations, relax as elastic materials on short time scales and as viscous liquids on long time scales. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,207 |
Precipitation of gypsum is studied in a HARDTAC (High-Aspect Ratio, Draft-Tube, Agitated Crystallizer) reactor, which is considered as the core crystallization unit of lots of wastewater treatment systems. Coupling Computational Fluid Dynamics (CFD) and population balance modelling to simulate precipitation can be a useful tool to come to a decision about upstream and downstream units. In the present study, we aim to validate such approach by investigating gypsum precipitation in a HARDTAC pilot unit and comparing experiments results with simulation. Measured nucleation and growth kinetics are used to feed the model. A comparison between experiments and simulations is presented in the case of gypsum precipitation with a given set of operating conditions. Good agreement is obtained for species concentrations, gypsum mass fraction and volumetric mean diameter but some discrepancies still remain between measured and simulated crystal size distribution. | The method of moments (MOM) may be used to determine the evolution of the lower-order moments of an unknown aerosol distribution. Previous applications of the method have been limited by the requirement that the equations governing the evolution of the lower-order moments be in closed form. Here a new approach, the quadrature method of moments (QMOM), is described. The dynamical equations for moment evolution are replaced by a quadrature-based approximate set that satisfies closure under a much broader range of conditions without requiring that the size distribution or growth law maintain any special mathematical form. The conventional MOM is recovered as a special case of the QMOM under those conditions, e.g., free-molecular growth, for which conventional closure is satisfied. The QMOM is illustrated for the growth of sulfuric acid-water aerosols and simulations of diffusion-controlled cloud droplet growth are presented. | ABSTRACTUNC-45A is an ubiquitously expressed protein highly conserved throughout evolution. Most of what we currently know about UNC-45A pertains to its role as a regulator of the actomyosin system... | eng_Latn | 26,208 |
Biofilms are communities of bacteria living embedded in a highly hydrated matrix composed of polysaccharides, proteins, and extracellular DNA. This life style confers numerous advantages to bacteria including protection against external threats. However, they also contribute to increase bacterial resistance against antimicrobials, an issue particularly relevant in dangerous infections. Due to the complexity of the matrix, few information is present in the literature on details of its architecture including the spatial distribution of the macromolecular components which might give hints on the way the biofilm scaffold is built up by bacteria. In this study, we investigated the possibility to combine well-established microbiological procedures with advanced microscopies to get information on composition and distribution of the macromolecular components of biofilm matrices. To this, confocal microscopy, diffraction-limited infrared (IR) spectral imaging, and atomic force microscopy (AFM) were used to explore biofilm produced by a clinical strain of Klebsiella pneumoniae. IR imaging permitted to have clues on how the biofilm grows and spreads on surfaces, and the local distribution of the components within it. Through the analysis of the pure component spectra, it was possible to assess the chemical and structural composition of the saccaridic matrix, confirming the data obtained by NMR. It was also possible to follow the time course of biofilm from 6 up to 48 h when the biofilm grew into a 3-dimensional multi-layered structure, characteristic of colonies of bacteria linked together by a complex matrix. In addition, nanoFTIR and AFM investigations allowed the estimation of biofilm growth in the vertical direction and the morphological analysis of bacterial colonies at different time points and the evaluation of the chemical composition at the nanoscale. | Modern medicine is facing the spread of biofilm-related infections. Bacterial biofilms are difficult to detect in routine diagnostics and are inherently tolerant to host defenses and antibiotic therapies. In addition, biofilms facilitate the spread of antibiotic resistance by promoting horizontal gene transfer. We review current concepts of biofilm tolerance with special emphasis on the role of the biofilm matrix and the physiology of biofilm-embedded cells. The heterogeneity in metabolic and reproductive activity within a biofilm correlates with a non-uniform susceptibility of enclosed bacteria. Recent studies have documented similar heterogeneity in planktonic cultures. Nutritional starvation and high cell density, two key characteristics of biofilm physiology, also mediate antimicrobial tolerance in stationary-phase planktonic cultures. Advances in characterizing the role of stress response genes, quorum sensing and phase variation in stationary-phase planktonic cultures have shed new light on tolerance mechanisms within biofilm communities. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 26,209 |
The aim of this study was to develop oral lyophilisates with improved meloxicam (MEL) dissolution, optimizing each step of the preparation by design of experiments. First, meloxicam nanosuspensions were prepared by high-pressure homogenization (HPH), using PVP, Poloxamer or PEG as stabilizers and were subjected to freeze-drying using mannitol as cryoprotectant. The effects of the stabilizers and cryoprotectant were assessed and an optimal formulation was generated within the Design Space where the particle sizes and the PDIs are at their lowest values. The optimal formulation was used at the preparation of oral lyophilisates. Sodium alginate (SA) and croscarmellose sodium (CCS) were tested as matrix forming agents and three different freezing regimes were applied. The formulation was optimized, choosing the polymer that yielded both high mechanical strength and fast MEL dissolution. Poloxamer led to particle size reduction down to 10.27% of the initial size, meaning 477.6±7.5nm, with a slight increase during freeze-drying process. PEG showed lower nanonizing capacity during HPH, but freeze-drying produced further diminution of the particle size. Since Poloxamer provided advanced size reduction while preserving MEL crystallinity, it was used for the optimized formulation containing 1% Poloxamer and 5% mannitol added before freeze-drying. SA showed good structural properties when compared to CCS and allowed fast MEL dissolution at low ratios. The optimal formulation contained 1.157% of SA was subjected to thermal treatment during freeze-drying. It disintegrated in 3.33s and released 77.14% of the MEL after 2min. The quality by design (QbD) approach for the development of pharmaceutical products ensured high quality of the dosage form and good understanding of the preparation process. | Drug nanoparticles prepared in a liquid medium are commonly freeze-dried for the preparation of an oral dosage in solid dosage form. The freezing rate is known to be a critical parameter for redispersible nanoformulations. However, there has been controversy as to whether a fast or slow freezing rate prevents irreversible aggregation. A systematic investigation is presented herein regarding the effect of both the molecular weight of the cryoprotectant and the freezing rate in order to elucidate the mechanism underlying irreversible aggregation. It was found that irreversible aggregation occurred during drying rather than freezing, although a proper freezing rate is critical. A more homogeneous distribution of the cryoprotectant and drug nanoparticles led to more redispersible powders. Thus, keeping the local concentration distribution of the nanoparticles and cryoprotectant fixed during the freezing step plays a critical role in how the freezing rate affects the redispersibility. The kinetic approach of excluding the tendency of ice crystal growth permitted an explanation of the controversial results. This study will facilitate an in-depth understanding of the aggregation process of nanoparticles or proteins during freeze-drying. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,210 |
Many proteins have the potential to aggregate into amyloid fibrils, which are associated with a wide range of human disorders including Alzheimer's and Parkinson's disease. In contrast to that of folded proteins, the thermodynamic stability of amyloid fibrils is not well understood: specifically the balance between entropic and enthalpic terms, including the chain entropy and the hydrophobic effect, are poorly characterised. Using simulations of a coarse-grained protein model we delineate the enthalpic and entropic contributions dominating amyloid fibril elongation, predicting a characteristic temperature-dependent enthalpic signature. We confirm this thermodynamic signature by performing calorimetric experiments and a meta-analysis over published data. From these results, we can also elucidate the necessary conditions to observe cold denaturation of amyloid fibrils. Overall, we show that amyloid fibril elongation is associated with a negative heat capacity, the magnitude of which correlates closely with the hydrophobic surface area that is buried upon fibril formation, highlighting the importance of hydrophobicity for fibril stability. | The conversion from soluble states into cross-beta fibrillar aggregates is a property shared by many different proteins and peptides and was hence conjectured to be a generic feature of polypeptide chains. Increasing evidence is now accumulating that such fibrillar assemblies are generally characterized by a parallel in-register alignment of beta-strands contributed by distinct protein molecules. Here we assume a universal mechanism is responsible for beta-structure formation and deduce sequence-specific interaction energies between pairs of protein fragments from a statistical analysis of the native folds of globular proteins. The derived fragment-fragment interaction was implemented within a novel algorithm, prediction of amyloid structure aggregation (PASTA), to investigate the role of sequence heterogeneity in driving specific aggregation into ordered self-propagating cross-beta structures. The algorithm predicts that the parallel in-register arrangement of sequence portions that participate in the fibril cross-beta core is favoured in most cases. However, the antiparallel arrangement is correctly discriminated when present in fibrils formed by short peptides. The predictions of the most aggregation-prone portions of initially unfolded polypeptide chains are also in excellent agreement with available experimental observations. These results corroborate the recent hypothesis that the amyloid structure is stabilised by the same physicochemical determinants as those operating in folded proteins. They also suggest that side chain-side chain interaction across neighbouring beta-strands is a key determinant of amyloid fibril formation and of their self-propagating ability. | We report enhancement of the mechanical stability of graphene through a one-step method to disperse gold nanoparticles on the pristine graphene without any added agent. | eng_Latn | 26,211 |
A point mutation, lysine 97 --> isoleucine (K97I), in a surface loop in the beta-sheet protein interleukin 1beta (IL-1beta), exhibits increased levels of inclusion body (IB) formation relative to the wild-type protein (WT) when expressed in Escherichia coli. Despite the common observation that less stable proteins are often found in IBs, K97I is more stable than WT. We examined the folding pathway of the mutant and wild-type proteins at pH 6.5 and 25 degrees C with manual-mixing and stopped-flow optical spectroscopy to determine whether changes in the properties of transiently populated species in vitro correlate with the observation of increased aggregation in vivo. The refolding reactions of the WT and K97I proteins are both described by three exponential processes. Two exponential processes characterize fast events (0.1-1.0 s) in folding while the third exponential process correlates with a slow (70 s) single pathway to and from the native state. The K97I replacement affects the earlier steps in the refolding pathway. Aggregation, absent in the WT refolding reaction, occurs in K97I above a critical protein concentration of 18 microM. This observation is consistent with an initial nucleation step mediating protein aggregation. Stopped-flow kinetic studies of the K97I aggregation process demonstrate that K97I aggregates most rapidly during the earliest refolding times, when unfolded protein conformers remain highly populated and the concentration of folding intermediates is low. Folding and aggregation studies together support a model in which the formation of stable folding intermediates afford protection against further K97I aggregation. | The objective of this study was to explore various testing methodologies suitable for characterizing sedimented or agglomerated material. To model this, bioCSL's split influenza virus vaccine, Fluvax® was utilized. The investigation was conducted on 5 dispensed lots of commercially manufactured vaccine, formulated for the 2013 Southern Hemisphere season. Vaccine syringes were initially inspected by visual tests; the material was then aseptically pooled for characterization assessment by microscopy and several agglomeration assays. All syringes passed bioCSL's description test where any fine or large sized particles of sediment observed in the vaccine were resuspended upon shaking; inverted light microscopy verified that the sediment morphology was consistent with influenza vaccine. Electron microscopic examination of pooled vaccine material demonstrated the presence of typical influenza structures including split virus, virosomes, whole virus particles and agglomerates. An optical density turbidity assay revealed relatively high protein recoveries in the vaccine supernatant post-centrifugation treatment, thus indicative of a well-dispersed vaccine formulation. This was corroborated by particle sizing analysis using dynamic light scattering which generated reproducible volume particle size distributions of a polydisperse nature. Ultraviolet-visible absorbance profiles further confirmed the presence of some agglomerated material. Data from all methods demonstrated consistent results between all batches of vaccine. Therefore, this investigation revealed the suitability and usefulness of the various methodologies in characterizing the appearance of agglomerated vaccine material. It is suggested that such methods may be applicable and beneficial for the development of a wider spectrum of heterogeneous and agglomerated formulations to provide safe, efficacious and superior quality biopharmaceutical products. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,212 |
The increase in concern over safe water for human consumption demands disinfection of water. Conventional chemical disinfection methods release counter ions into the treated water and they impair human health significantly. The present investigation was focused on the disinfection of pathogenic bacteria via a bio-disinfection route using a prodigiosin-impregnated cellulose column reactor (PICCR). Escherichia coli and Bacillus cereus were chosen as model pathogens to validate the efficiency of the PICCR for pathogen removal from water. The pathogen removal efficiency was evaluated by the pour plate method, regrowth ability in nutrient broth and quantitative estimation of live and dead cells using fluorescent microscopy. The PICCR showed effective reduction of E. coli by 97.31% and B. cereus by 97.33%. Further, bacterial cell membrane damage by bio-disinfection was verified through analysis of the residual protein and nucleic acid in the treated water using UV-visible spectroscopy, a trans-illuminometer and SDS PAGE. The proposed PICCR was found to be effective for the removal of pathogens from water and this may be regarded as a viable purification technique for drinking water. | As the nanotechnological applications have taken over in different fields, their applications for water and wastewater treatment is also surfacing as a fast-developing and very promising area. Recent advancements in nanotechnological science and engineering advise that many of the waterborne pathogens could be culminated or debilitated using nanobiosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes, nanobioreactors, nanoparticle-enhanced filtration among other products, and processes resulting from the development of nanotechnology. A detailed insight has been provided for advanced techniques such as photochemical (photocatalytic and advanced oxidation processes) applications of metal oxide nanoparticles, nanomembrane technology, bioinspired nanomaterials, and nanotechnological innovations (nano-Ag, fullerenes, nanotubes, and molecularly imprinted polymers, etc.), which prove to be highly potential as well as promising and cost-effective. However, there are still some shortcomings and challenges that must be overcome which will be looked upon in this chapter. | The most conspicuous feature in previous phaeophycean phylogenies is a large polytomy known as the brown algal crown radiation (BACR). The BACR encompasses 10 out of the 17 currently recognized brown algal orders. A recent study has been able to resolve a few nodes of the BACR, suggesting that it may be a soft polytomy caused by a lack of signal in molecular markers. The present work aims to refine relationships within the BACR and investigate the nature and timeframe of the diversification in question using a dual approach. A multi-marker phylogeny of the brown algae was built from 10 mitochondrial, plastid and nuclear loci (>10,000 nt) of 72 phaeophycean taxa, resulting in trees with well-resolved inter-ordinal relationships within the BACR. Using Bayesian relaxed molecular clock analysis, it is shown that the BACR is likely to represent a gradual diversification spanning most of the Lower Cretaceous rather than a sudden radiation. Non-molecular characters classically used in ordinal delimitation were mapped on the molecular topology to study their evolutionary history. | eng_Latn | 26,213 |
Background ::: Extracellular polymeric matrix (EPM) is a complex component of the organo-mineral assemblages created by biological soil crusts (BSCs). Mainly of polysaccharidic origin, it embeds soil and sediments and provides key benefits to the crust community. Services provided include: sediment cohesion and resistance to erosion, moisture provision, protection from external harmful factors, as well as support to plant establishment and growth. EPM is the product of BSC microbial community, and it is constituted by exopolysaccharides (EPS) associated to other substances, organized in a three-dimensional structure having different levels of gelation, and degrees of condensation. | Soil erosion and subsequent degradation has been a contributor to societal collapse in the past and is one of the major expressions of desertification in arid regions. The revised universal soil loss equation (RUSLE) models soil lost to water erosion as a function of climate erosivity (the degree to which rainfall can result in erosion), topography, soil erodibility, and land use/management. The soil erodibility factor (K) is primarily based upon inherent soil properties (those which change slowly or not at all) such as soil texture and organic matter content, while the cover/management factor (C) is based on several parameters including biological soil crust (BSC) cover. We examined the effect of two more precise indicators of BSC development, chlorophyll a and exopolysaccharides (EPS), upon soil stability, which is closely inversely related to soil loss in an erosion event. To examine the relative influence of these elements of the C factor to the K factor, we conducted our investigation across eight strongly differing soils in the 0.8 million ha Grand Staircase-Escalante National Monument. We found that within every soil group, chlorophyll a was a moderate to excellent predictor of soil stability (R 2 ¼ 0.21–0.75), and consistently better than EPS. Using a simple structural equation model, we explained over half of the variance in soil stability and determined that the direct effect of chlorophyll a was 3� more important than soil group in determining soil stability. Our results suggest that, holding the intensity of erosive forces constant, the acceleration or reduction of soil erosion in arid landscapes will primarily be an outcome of management practices. This is because the factor which is most influential to soil erosion, BSC development, is also among the most manageable, implying that water erosion in drylands has a solution. | Structural analysis of flexible macromolecular systems such as intrinsically disordered or multidomain proteins with flexible linkers is a difficult task as high-resolution techniques are barely applicable. A new approach, ensemble optimization method (EOM), is proposed to quantitatively characterize flexible proteins in solution using small-angle X-ray scattering (SAXS). The flexibility is taken into account by allowing for the coexistence of different conformations of the protein contributing to the experimental scattering pattern. These conformers are selected using a genetic algorithm from a pool containing a large number of randomly generated models covering the protein configurational space. Quantitative criteria are developed to analyze the EOM selected models and to determine the optimum number of conformers in the ensemble. Simultaneous fitting of multiple scattering patterns from deletion mutants, if available, provides yet more detailed local information about the structure. The efficiency of EOM is demonstrated in model and practical examples on completely or partially unfolded proteins and on multidomain proteins interconnected by linkers. In the latter case, EOM is able to distinguish between rigid and flexible proteins and to directly assess the interdomain contacts. | eng_Latn | 26,214 |
The non-linear dynamics of a series of salt-free surfactant solutions is investigated via a combination of TEM imaging, shear rheology and capillary breakup extensional rheometery. Surfactant solutions contain Hexadecyltrimethylammonium p-toluenesulfonate (CTAT) in de-ionized water. At low surfactant concentrations, 0.7 wt% λ E ≈ 0.03 s. At higher concentrations, 1.1 wt% ≤ c Tr ≈ 3, for higher concentrations. This finding is in-line with the structural parameters inferred from the shear rheology and also the TEM images. Therefore, we confirm that the extensional rheology is sensitive to structural transitions near the critical concentration. Finally, we show that the ratio of the extensional relaxation time to the shear relaxation time, λ E / λ , is always less than unity regardless of whether relaxation is dominated by reptation or breakage of the wormlike micelles. | Formation and breakup of fluid threads is pervasive in nature and technology, where high extensibility of fluid filaments and extended filament lifetimes are commonly observed as a consequence of fluid viscoelasticity. In contrast, threads of low viscous Newtonian fluids like water rupture quickly. Here, we demonstrate that a unique banding instability during filament thinning of model surfactant solutions, with a viscosity close to water and no measurable elasticity, leads to extremely long filament lifetimes and to the formation of remarkably long threads. Complementary measurements in planar extension as well as in shear reveal that this flow instability is characterized by a multivalued stress, arising beyond a critical strain rate, irrespective of flow kinematics. Our work reports the first observation of such phenomena during extensional deformation and provides a unifying view on instabilities in complex flow fields. | A study has been made of the presence and reactivity of the most commonly used surfactants, both anionic (linear alkylbenzene sulfonates, LAS, and alkyl ethoxysulfates, AES) and non-ionic (alcohol polyethoxylates, AEOs, and nonylphenol polyethoxylates, NPEOs), in water and surface sediments from the middle stretch of the Guadalete River in SW Spain (12 stations). Average values were between 0.1 and 3.7 mg kg(-1) in sediment, and between 0.2 and 37 μg L(-1) in water. The sorption of surfactants was dominated by hydrophobic mechanisms, so those homologues having longer alkyl chains (e.g. C(18)AEO) showed higher relative percentages and concentrations in sediments compared with water. Local and sharply higher concentrations of these compounds were observed at three sampling stations (7, 9 and 12), indicating the occurrence of wastewater discharges into the river. By analysing the distributions of different surfactant homologues and their metabolites we were able to distinguish between sewage contamination from sources discharging treated and untreated wastewaters. Upstream (stations 1-2), LAS concentrations were below 30 μg L(-1) and the composition of their degradation intermediates (sulfophenyl carboxylic acids, SPCs) (160 μg L(-1)) was dominated by short-chain homologues (C(6)-C(9)SPCs), indicating that the degradation of this surfactant is at an advanced stage. The highest concentration (487 μg L(-1)) of SPCs was detected near the effluent outlet of a sewage treatment plant (STP) (station 12). Sampling stations (7 and 9) affected by untreated wastewater discharges were the only ones showing the presence of the most reactive and biodegradable SPC isomers and homologues (e.g. C(11)SPC). Here, LAS reached the highest concentration values measured (>2 mg L(-1)), and showed a homologue distribution closer to that of commercial mixtures than LAS found at the other stations. | eng_Latn | 26,215 |
Isotactic polypropylene (iPP) rich in β crystal modification (constituting 92% of crystalline phase) was deformed by the plane-strain compression with constant true strain rate, at room temperature. The evolution of phase structure, morphology and orientation was studied by DSC, X-ray and SEM. The deformation sequence and the active deformation mechanisms were found out. The most important mechanisms were interlamellar slip operating in the amorphous layers, resulting in numerous fine deformation bands due to localization of deformation and the crystallographic slip systems, including the (110)[001] chain slip and (110)[1 1 ¯ 0] transverse slip. Shear within deformation bands leads to β → smectic and β → α solid state phase transformations. At room temperature the β → smectic transformation appeared to be the primary transformation, yielding the oriented smectic phase with high concentration of 19 wt.% at the true strain of e = 1.49. The β → α yields only about 4 wt.% of new α-phase at the same strain. As a result of the deformation and phase transformation within numerous fine deformation bands β-lamellae are locally destroyed and fragmented into smaller crystals. Another deformation mechanism is the cooperative kinking of lamellae, leading to their reorientation and formation of a chevron-like lamellar arrangement. At high strains, above e = 1, an advanced crystallographic slip and high stretch of amorphous material due to interlamellar shear bring further heavy fragmentation of lamellar crystals, earlier fragmented partially by deformation bands. This fragmentation is followed by fast rotation of small unconstrained crystallites with chain axis towards the direction of flow, FD. This process leads to development of the final texture of the highly deformed β-iPP with molecular axis of both crystalline and smectic phases oriented along FD. | A highly efficient compound nucleating agent of carboxylated graphene/calcium pimelate (Gra/CaPi) for isotactic polypropylene (iPP) was prepared. The structure of Gra/CaPi was investigated by Fourier-transform infrared spectroscopy. The effects of Gra/CaPi on the crystallization and melting behaviors and crystalline morphology of iPP were investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy. The results showed that CaPi and Gra were combined by chemical bonds, improved the dispersibility and nucleation ability of Gra in iPP. When the addition amount of Gra/CaPi in iPP was 0.3 mass%, the crystallization peak temperature was increased by 8.0 °C and the relative content of β-crystal in iPP reached up to 0.868 compared with that of pure iPP. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,216 |
The bacterial flagellar motor is an ion-powered transmembrane protein complex which drives swimming in many bacterial species. The motor consists of a cytoplasmic 'rotor' ring and a number of 'stator' units, which are rooted to the cell wall of the bacterium. Recently, it has been shown that the number of engaged torque-generating 'stator' units in the motor varies depending on the external load the motor experiences, and suggested that mechanosensing in the flagellar motor is driven via a 'catch bond' mechanism in the motor's stator units. Here, we present a method that allows us to measure stator dynamics across a large range of external loads, including near the zero-torque limit: By attaching superparamagnetic beads to the flagellar hook, we can control the motor's speed via a rotating magnetic field. Here, we manipulate the motor to three different speed levels in two different ion-motive force (IMF) conditions. Our results suggest that stator dynamics are affected by the torque that each stator unit experiences, manifested as a function of the energy available to it in the form of IMF and the speed at which the rotor is driven. | A cell of the bacterium Escherichia coli was tethered covalently to a glass coverslip by a single flagellum, and its rotation was stopped by using optical tweezers. The tweezers acted directly on the cell body or indirectly, via a trapped polystyrene bead. The torque generated by the flagellar motor was determined by measuring the displacement of the laser beam on a quadrant photodiode. The coverslip was mounted on a computer-controlled piezo-electric stage that moved the tether point in a circle around the center of the trap so that the speed of rotation of the motor could be varied. The motor generated ≈4500 pN nm of torque at all angles, regardless of whether it was stalled, allowed to rotate very slowly forwards, or driven very slowly backwards. This argues against models of motor function in which rotation is tightly coupled to proton transit and back-transport of protons is severely limited. | A cell of the bacterium Escherichia coli was tethered covalently to a glass coverslip by a single flagellum, and its rotation was stopped by using optical tweezers. The tweezers acted directly on the cell body or indirectly, via a trapped polystyrene bead. The torque generated by the flagellar motor was determined by measuring the displacement of the laser beam on a quadrant photodiode. The coverslip was mounted on a computer-controlled piezo-electric stage that moved the tether point in a circle around the center of the trap so that the speed of rotation of the motor could be varied. The motor generated ≈4500 pN nm of torque at all angles, regardless of whether it was stalled, allowed to rotate very slowly forwards, or driven very slowly backwards. This argues against models of motor function in which rotation is tightly coupled to proton transit and back-transport of protons is severely limited. | eng_Latn | 26,217 |
We numerically investigate the hydrodynamic interaction of swimming organisms at small to intermediate Reynolds number regimes, i.e., Re∼O(0.1-100), where inertial effects are important. The hydrodynamic interaction of swimming organisms in this regime is significantly different from the Stokes regime for microorganisms, as well as the high Reynolds number flows for fish and birds, which involves strong flow separation and detached vortex structures. Using an archetypal swimmer model, called a "squirmer," we find that the inertial effects change the contact time and dispersion dynamics of a pair of pusher swimmers, and trigger hydrodynamic attraction for two pullers. These results are potentially important in investigating predator-prey interactions, sexual reproduction, and the encounter rate of marine organisms such as copepods, ctenophora, and larvae. | We investigate the dynamics of two-dimensional soft vesicles filled with chiral active particles by employing the overdamped Langevin dynamics simulation. The unidirectional rotation is observed for soft vesicles, and the rotational angular velocity of vesicles depends mainly on the area fraction (ρ) and angular velocity (ω) of chiral active particles. There exists an optimal parameter for ω at which the rotational angular velocity of vesicle takes its maximal value. Meanwhile, at low concentration the continuity of curvature is destroyed seriously by chiral active particles, especially for large ω, and at high concentration the chiral active particles cover the vesicle almost uniformly. In addition, the center-of-mass mean square displacement for vesicles is accompanied by oscillations at short timescales, and the oscillation period of diffusion for vesicles is consistent with the rotation period of chiral active particles. The diffusion coefficient of vesicle decreases monotonously with increasing the angular velocity ω of chiral active particles. Our investigation can provide a few designs for nanofabricated devices that can be driven in a unidirectional rotation by chiral active particles or could be used as drug-delivery agent. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,218 |
Monte Carlo simulations were performed to study the conformational changes of negatively charged model peptides dissolved in water adsorbed onto charged surfaces. 8-, 16-, and 20-residues peptides were used, each of them consisted of repeating diblock units of aspartic acid (ASP, polar amino acid) and isoleucine (ILE, nonpolar amino acid) residues. We found that a water patch was retained at the charged surface, separating the peptide from it. We believed that these water molecules were primarily responsible for giving a particular orientation to the peptide at the surface. Water did play a role to some extent in the structural stability of the 8-residues peptide. However, for higher chain lengths (16-residues and 20-residues), the intrinsic hydrogen-bonding network (or intrinsic structural stability) showed a predominant effect over hydrophobic dehydration for the stability of the peptide at the surface. | Nanobiocatalysis is a new frontier of emerging nanosized material support in enzyme immobilization application. This paper is about a comprehensive review on cellulose nanofibers (CNF), including their structure, surface modification, chemical coupling for enzyme immobilization, and potential applications. The CNF surface consists of mainly -OH functional group that can be directly interacted weakly with enzyme, and its binding can be improved by surface modification and interaction of chemical coupling that forms a strong and stable covalent immobilization of enzyme. The knowledge of covalent interaction for enzyme immobilization is important to provide more efficient interaction between CNF support and enzyme molecule. Enzyme immobilization onto CNF is having potential for improving enzymatic performance and production yield, as well as contributing toward green technology and sustainable sources. | A continuous flow atmospheric pressure laser desorption/ionization technique using a porous stainless steel probe and a 6–7-µm-band mid-infrared tunable laser was developed. This ion source is capable of direct ionization from a continuous flow with a high temporal stability. The 6–7-µm wavelength region corresponds to the characteristic absorption bands of various molecular vibration modes, including O–H, C=O, CH3 and C–N bonds. Consequently, many organic compounds and solvents, including water, have characteristic absorption peaks in this region. This ion source requires no additional matrix, and utilizes water or acetonitrile as the solvent matrix at several absorption peak wavelengths (6.05 and 7.27 µm, respectively). The distribution of multiply-charged peptide ions is extremely sensitive to the temperature of the heated capillary, which is the inlet of the mass spectrometer. This ionization technique has potential for the interface of liquid chromatography/mass spectrometry (LC/MS). | eng_Latn | 26,219 |
The well-known Watson-Crick model for the DNA (and RNA) structures is critically considered. Doubts about the fact that the composition of the DNA-water samples used by Watson and Crick corresponded to the composition of the system in vivo are supported by modeling of the DNA-water system and by experi- ments with the polyacrylamide-water system. In order to formulate an alternative hypothesis on the DNA (RNA) structure, we examined the available data on amino and carbonyl groups in aliphatic monoamines and diamines, on purines and pyrimidines incorporated into DNA and RNA, and on gaseous and fluid hydrates. An original hydrate model for the DNA (RNA)-water system is proposed. For the equilibrium DNA (RNA)-water system, the helix step (0.567 nm), the number of pairs of nitrogen bases per helix convolution (11.25), and the density (1.161 g/cm 3 ) are calculated on the basis of this model and using the X-ray data of Wilkins, Franklin, et al . Our model predicts the density of the nonequilibrium DNA-water samples used by Wilkins and Franklin to be 1.351 g/cm 3 , in full agreement with their earlier measurements (1.34-1.39 g/cm 3 ). Assumptions on the nature of processes occurring at various stages of mitosis are presented. | The Life Origination Hydrate Theory (LOH-Theory) considers the life origination process as a sequence of thermodynamically caused regular and inevitable chemical transformations regulated by universal physical and chemical laws. The LOH-Theory bears on a number of experimental, thermodynamic, observation, and simulation researches. N-bases, riboses, nucleosides, and nucleotides and DNAs and RNAs are formed repeatedly within structural cavities of localizations of underground and underseabed honeycomb CH4-hydrate deposits from CH4 and nitrate and phosphate ions that diffused into the hydrate structures; proto-cells and their agglomerates originated from these DNAs and from the same minerals in the semi-liquid soup after liquation of the hydrate structures. Each localization gave rise to a multitude of different DNAs and living organisms. The species diversity is caused by the spatial and temporal repeatability of the processes of living matter origination under similar but not identical conditions, multiplicity of the DNA forms in each living matter origination event, variations in the parameters of the native medium, intraspecific variations, and interspecific variations. The contribution of the last to the species diversity is, likely, significant for prokaryotes and those eukaryotes that are only at low steps of their biological organization; however, in the light of the LOH-Theory, of available long-term paleontological investigations, and of studies of reproduction of proliferous organisms, we conclude that, in toto, the contribution of interspecific variations to the species diversity was earlier overestimated by some researchers. The reason of this overestimation is that origination of scores of «spores» of different organisms in any one event and multiple reproductions of such events in time and Earth's space were not taken into consideration. | We report enhancement of the mechanical stability of graphene through a one-step method to disperse gold nanoparticles on the pristine graphene without any added agent. | eng_Latn | 26,220 |
We report a direct comparison of the local structure of the hydrophobic hydration of krypton in both the liquid and solid states by the extended x-ray absorption fine structure spectroscopy technique. The evolution of an ordered hydration shell of the nonpolar gas moiety is followed as the liquid to solid phase transition progresses. The formation of a clathrate cage structure from the more disordered liquid state hydration shell is clearly demonstrated. | Amphiphiles are synthetic or natural molecules with the ability to self-assemble into a wide variety of structures including micelles, vesicles, nanotubes, nanofibers, and lamellae. Self-assembly processes of amphiphiles have been widely used to mimic biological systems, such as assembly of lipids and proteins, while their integrated actions allow the performance of highly specific cellular functions which has paved a way for bottom-up bionanotechnology. While amphiphiles self-assembly has attracted considerable attention for decades due to their extensive applications in material science, drug and gene delivery, recent developments in nanoscience stimulated the combination of the simple approaches of amphiphile assembly with the advanced concept of supramolecular self-assembly for the development of more complex, hierarchical nanostructures. Introduction of stimulus responsive supramolecular amphiphile assembly-disassembly processes provides particularly novel approaches for impacting bionanotechnology applications. Leading examples of these novel self-assembly processes can be found, in fact, in biosystems where assemblies of different amphiphilic macrocomponents and their integrated actions allow the performance of highly specific biological functions. In this perspective, we summarize in this tutorial review the basic concept and recent research on self-assembly of traditional amphiphilic molecules (such as surfactants, amphiphile-like polymers, or lipids) and more recent concepts of supramolecular amphiphiles assembly which have become increasingly important in emerging nanotechnology. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,221 |
Nanoparticles (NPs) grafted with organic layers form hybrids able to retain their unique properties through integration into the mesoscopic scale. The organic layer structure and response often determine the functionality of the hybrids on the mesoscopic length scale. Using molecular dynamics (MD) simulations, we probe the conformation of luminescent rigid polymers, dialkyl poly(p-phenylene ethynylene)s (PPE), end-grafted onto a silica nanoparticle in different solvents as the molecular weights and polymer coverages are varied. We find that, in contrast to NP-grafted flexible polymers, the chains are fully extended independent of the solvent. In toluene and decane, which are good solvents, the grafted PPEs chains assume a similar conformation to that observed in dilute solutions. In water, which is a poor solvent for the PPEs, the polymer chains form one large cluster but remain extended. The radial distribution of the chains around the core of the nanoparticle is homogeneous in good solvents, whereas in poor solvents clusters are formed independent of molecular weights and coverages. The clustering is distinctively different from the response of grafted flexible and semiflexible polymers. | Environmentally responsive surface-modified nanoparticles are colloidal nanoparticles coated with, at least, two physicochemically distinct surface groups. Recent advances in the synthesis and production of nanoparticles have enabled the production of environmentally responsive surface-modified nanoparticles with both hydrophilic and hydrophobic surface groups. These nanoparticles act like colloidal surfactants. In this paper, environmentally responsive surface-modified silica nanoparticles are synthesized and used for enhancement of oil recovery. For this purpose, silica nanoparticles are coated with polyethylene glycol chains as hydrophilic agent and propyl chains as hydrophobic agent at various quantities, and their ability to modulate oil–water interface properties and oil recovery is examined. Oil–water interfacial tension and water surface tension are decreased by 50 % in the presence of silica nanoparticles coated with both agents. Measuring oil-drop contact angle on oil-wetted glass slides and carbonate rock sections, after aging in various surface-modified silica nanofluids, indicates that the wettability of various oil-wetted surfaces is modified from strongly oil-wet to water-wet. Flooding nanofluids to glass micro-models and pore-level investigations demonstrate that surface modification of silica nanoparticles, specially, with both hydrophilic and hydrophobic agents improves considerably their performance in increasing oil recovery and wettability alteration. | A study has been made of the presence and reactivity of the most commonly used surfactants, both anionic (linear alkylbenzene sulfonates, LAS, and alkyl ethoxysulfates, AES) and non-ionic (alcohol polyethoxylates, AEOs, and nonylphenol polyethoxylates, NPEOs), in water and surface sediments from the middle stretch of the Guadalete River in SW Spain (12 stations). Average values were between 0.1 and 3.7 mg kg(-1) in sediment, and between 0.2 and 37 μg L(-1) in water. The sorption of surfactants was dominated by hydrophobic mechanisms, so those homologues having longer alkyl chains (e.g. C(18)AEO) showed higher relative percentages and concentrations in sediments compared with water. Local and sharply higher concentrations of these compounds were observed at three sampling stations (7, 9 and 12), indicating the occurrence of wastewater discharges into the river. By analysing the distributions of different surfactant homologues and their metabolites we were able to distinguish between sewage contamination from sources discharging treated and untreated wastewaters. Upstream (stations 1-2), LAS concentrations were below 30 μg L(-1) and the composition of their degradation intermediates (sulfophenyl carboxylic acids, SPCs) (160 μg L(-1)) was dominated by short-chain homologues (C(6)-C(9)SPCs), indicating that the degradation of this surfactant is at an advanced stage. The highest concentration (487 μg L(-1)) of SPCs was detected near the effluent outlet of a sewage treatment plant (STP) (station 12). Sampling stations (7 and 9) affected by untreated wastewater discharges were the only ones showing the presence of the most reactive and biodegradable SPC isomers and homologues (e.g. C(11)SPC). Here, LAS reached the highest concentration values measured (>2 mg L(-1)), and showed a homologue distribution closer to that of commercial mixtures than LAS found at the other stations. | eng_Latn | 26,222 |
Due to their high enzymatic activity, the sugar-non-specific endonucleases from Serratia marcescens and Anabaena can be used for a number of applications, such as the removal of contaminating genetic material from biological preparations, footprinting studies, and the determination of nucleic acids in biochemical samples. These methods would benefit from immobilized nucleases. For this purpose, a single cysteine residue was added at the N -terminus of the Serratia and Anabaena nucleases and subsequently modified with a maleimide–biotin conjugate. Alternatively, a biotin acceptor domain was fused to the Anabaena nuclease, allowing biotinylation during expression in E. coli without a further chemical step. The attachment of biotin-modified nucleases to streptavidin-coated paramagnetic beads and to streptavidin-coated surface plasmon resonance sensor chips (to study interactions with substrate and inhibitor) worked well when aggregates present in the protein preparations were removed by ultrafiltration. These methods should be of general use for similar enzyme systems. | The ribosome is the macromolecular machine responsible for translating the genetic code into polypeptide chains. Despite impressive structural and kinetic studies of the translation process, a number of challenges remain with respect to understanding the dynamic properties of the translation apparatus. Single-molecule techniques hold the potential of characterizing the structural and mechanical properties of macromolecules during their functional cycles in real time. These techniques often necessitate the specific coupling of biologically active molecules to a surface. Here, we describe a procedure for such coupling of functionally active ribosomes that permits single-molecule studies of protein synthesis. Oxidation with NaIO4 at the 3′ end of 23S rRNA and subsequent reaction with a biotin hydrazide produces biotinylated 70S ribosomes, which can be immobilized on a streptavidin-coated surface. The surface-attached ribosomes are fully active in poly(U) translation in vitro, synthesizing poly(Phe) at a rate of 3–6 peptide bonds/s per active ribosome at 37°C. Specificity of binding of biotinylated ribosomes to a streptavidin-coated quartz surface was confirmed by observation of individual fluorescently labeled, biotinylated 70S ribosomes, using total internal reflection fluorescence microscopy. Functional interactions of the immobilized ribosomes with various components of the protein synthesis apparatus are shown by use of surface plasmon resonance. | The effect of guanidine or heat on the haemagglutinin and neuraminidase of thirty strains of influenza virus showed a considerable variation among the strains in the sensitivity of the two surface glycoprotein subunits of the virus to these agents. The kinetics of inactivation was complex, and could not be expressed in terms of a simple mathematical exponential function. However, correlation diagrams plotted with the logarithm of the residual haemagglutinin or neuraminidase activity at a selected point (30 minutes) in the inactivation process showed a general pattern of grouping, which in the case of the haemagglutinin did not completely reflect the conventional serological classification of the strains. The neuraminidase correlation diagram on the other hand evidently reflected the antigenic grouping of the strains into subtypes, N1 and N2, and also differences were detected in the behaviour of strains showing antigenic “drift” within a subtype. Because guanidine attacks the relatively weaker polar linkages especially hydrogen bonding, its differing effects on the surface glycoproteins of different strains reflect alterations in the molecular configuration of the enzyme molecule. Such changes are also probably associated with antigenic changes such as from one subtype to another (“shift”) or in antigenic “drift”. | eng_Latn | 26,223 |
The competition between a spherical macroion and a polyelectrolyte in complexation with an oppositely charged flexible polyelectrolyte has been studied by means of Monte Carlo simulations. A simple model system with focuson the electrostatic interactions has been used to investigate under what conditions the macroion in a polyelectrolyte-macroion complex (excess of polyelectrolyte charges) is exchanged with a polyelectrolyte. It is shown that the macroion is released when the charge of the added polyelectrolyte equals or exceeds that of the polyelectrolyte in the complex. The effect of the polyelectrolyte length, flexibility, and linear charge density on the macroion release has been investigated. | Various models of the complex formation between polyelectrolyte chains and oppositely charged macroions are reviewed. In recent years, a great deal of knowledge of the multitude of possible polyelectrolyte conformations at the macroion surface has been accumulated, which consequently has led to increasing interest in using such complexes in the design of nanomaterials. This review focuses on key studies relating to the effects of various physico-chemical parameters on complex formation and areas for future research are identified. | Various models of the complex formation between polyelectrolyte chains and oppositely charged macroions are reviewed. In recent years, a great deal of knowledge of the multitude of possible polyelectrolyte conformations at the macroion surface has been accumulated, which consequently has led to increasing interest in using such complexes in the design of nanomaterials. This review focuses on key studies relating to the effects of various physico-chemical parameters on complex formation and areas for future research are identified. | eng_Latn | 26,224 |
The mechanism by which antifreeze proteins (AFPs) irreversibly bind to ice has not yet been resolved. The ice-binding site of an AFP is relatively hydrophobic, but also contains many potential hydrogen bond donors/acceptors. The extent to which hydrogen bonding and the hydrophobic effect contribute to ice binding has been debated for over 30 years. Here we have elucidated the ice-binding mechanism through solving the first crystal structure of an Antarctic bacterial AFP. This 34-kDa domain, the largest AFP structure determined to date, folds as a Ca(2+)-bound parallel beta-helix with an extensive array of ice-like surface waters that are anchored via hydrogen bonds directly to the polypeptide backbone and adjacent side chains. These bound waters make an excellent three-dimensional match to both the primary prism and basal planes of ice and in effect provide an extensive X-ray crystallographic picture of the AFPice interaction. This unobstructed view, free from crystal-packing artefacts, shows the contributions of both the hydrophobic effect and hydrogen bonding during AFP adsorption to ice. We term this mode of binding the "anchored clathrate" mechanism of AFP action. | Antifreeze proteins (AFPs) prevent uncontrolled ice formation in organisms exposed to subzero temperatures by binding irreversibly to specific planes of nascent ice crystals. To understand the thermodynamic driving forces and kinetic mechanism of AFP activity, it is necessary to characterize the hydration behavior of these proteins in solution. With this aim, we have studied the hyperactive insect AFP from Tenebrio molitor (TmAFP) with the (17)O magnetic relaxation dispersion (MRD) method, which selectively monitors the rotational motion and exchange kinetics of water molecules on picosecond-microsecond time scales. The global hydration behavior of TmAFP is found to be similar to non-antifreeze proteins, with no evidence of ice-like or long-ranged modifications of the solvent. However, two sets of structural water molecules, located within the core and on the ice-binding face in the crystal structure of TmAFP, may have functional significance. We find that 2 of the 5 internal water molecules exchange with a residence time of 8 +/- 1 micros at 300 K and a large activation energy of approximately 50 kJ mol(-1), reflecting intermittent large-scale conformational fluctuations in this exceptionally dense and rigid protein. Six water molecules arrayed with ice-like spacing in the central trough on the ice-binding face exchange with bulk water on a sub-nanosecond time scale. The combination of high order and fast exchange may allow these water molecules to contribute entropically to the ice-binding affinity without limiting the absorption rate. | Antifreeze proteins (AFPs) prevent uncontrolled ice formation in organisms exposed to subzero temperatures by binding irreversibly to specific planes of nascent ice crystals. To understand the thermodynamic driving forces and kinetic mechanism of AFP activity, it is necessary to characterize the hydration behavior of these proteins in solution. With this aim, we have studied the hyperactive insect AFP from Tenebrio molitor (TmAFP) with the (17)O magnetic relaxation dispersion (MRD) method, which selectively monitors the rotational motion and exchange kinetics of water molecules on picosecond-microsecond time scales. The global hydration behavior of TmAFP is found to be similar to non-antifreeze proteins, with no evidence of ice-like or long-ranged modifications of the solvent. However, two sets of structural water molecules, located within the core and on the ice-binding face in the crystal structure of TmAFP, may have functional significance. We find that 2 of the 5 internal water molecules exchange with a residence time of 8 +/- 1 micros at 300 K and a large activation energy of approximately 50 kJ mol(-1), reflecting intermittent large-scale conformational fluctuations in this exceptionally dense and rigid protein. Six water molecules arrayed with ice-like spacing in the central trough on the ice-binding face exchange with bulk water on a sub-nanosecond time scale. The combination of high order and fast exchange may allow these water molecules to contribute entropically to the ice-binding affinity without limiting the absorption rate. | eng_Latn | 26,225 |
The interaction of antimicrobial peptides with membranes is a key factor in determining their biological activity. In this study we have synthesized a series of minimized cecropin-mellitin hybrid peptides each containing a single cysteine residue, modified the cysteine with the sulfhydryl-specific methanethiosulfonate spin-label, and used electron paramagnetic resonance spectroscopy to measure membrane-binding affinities and determine the orientation and localization of peptides bound to membranes that mimic the bacterial cytoplasmic membrane. All of the peptides were unstructured in aqueous solution but underwent a significant conformational change upon membrane binding that diminished the rotational mobility of the attached spin-label. Apparent partition coefficients were similar for five of the six constructs examined, indicating that location of the spin-label had little effect on peptide binding as long as the attachment site was in the relatively hydrophobic C-terminal domain. Depth measurements based on accessibility of the spin-labeled sites to oxygen and nickel ethylenediaminediacetate indicated that at high lipid/peptide ratios these peptides form a single alpha-helix, with the helical axis aligned parallel to the bilayer surface and immersed approximately 5 A below the membrane-aqueous interface. Such a localization would provide exposure of charged/polar residues on the hydrophilic face of the amphipathic helix to the aqueous phase, and allow the nonpolar residues along the opposite face of the helix to remain immersed in the hydrophobic phase of the bilayer. These results are discussed with respect to the mechanism of membrane disruption by antimicrobial peptides. | Despite their potent antimicrobial activity, the usefulness of antimicrobial peptides (AMPs) as antibiotics has been limited by their toxicity to eukaryotic cells and a lack of stability in vivo. In the present study we examined the effects of introducing D-lysine residues into a 15-residue hybrid AMP containing residues 1–7 of cecropin A and residues 2–9 of melittin (designated CM15). Diastereomeric analogs of CM15 containing between two and five D-lysine substitutions were evaluated for their antimicrobial activity, lysis of human erythrocytes, toxicity to murine macrophages, ability to disrupt cell membranes, and protease stability. All of the analogs caused rapid permeabilization of the Staphylococcus aureus cell envelope, as indicated by uptake of SYTOX green. Permeabilization of the plasma membrane of RAW264.7 macrophages was also observed for CM15, but this was substantially diminished for the D-lysine containing analogs. The introduction of D-lysine caused moderate decreases in antimicrobial activity for all analogs studied, with a much more pronounced reduction in toxicity to eukaryotic cells, leading to marked improvements in antimicrobial efficacy. Circular dichroism studies indicated a progressive loss of helical secondary structure upon introduction of D-lysine residues, with a good correspondence between helical content and eukaryotic cell cytotoxicity. Overall, these studies indicate that disruption of amphipathic secondary structure reduces both antimicrobial activity and eukaryotic cell toxicity, but that the reduction in eukaryotic cell cytotoxicity is more pronounced, leading to an overall gain in antimicrobial selectivity. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,226 |
The equilibrium unfolded state of disulfide-intact bovine pancreatic ribonuclease A is a heterogeneous mixture of unfolded species. Previously, four unfolded species have been detected experimentally. They are Uvf, Uf, UsII, and UsI which have refolding time constants on the millisecond, millisecond to second, second to tens of seconds, and hundreds of seconds time scales, respectively. In the current study, the refolding pathway of the protein was investigated under favorable folding conditions of 0.58 M GdnHCl, pH 5.0, and 15 degrees C. In addition to the above four unfolded species, the presence of a fifth unfolded species was detected. It has a refolding time constant on the order of 2 s under the conditions employed. This new unfolded species is labeled Um, for medium-refolding species. Single-jump refolding experiments monitored by tyrosine burial and by cytidine 2'-monophosphate inhibitor binding indicate that the different unfolded species refold to the native state along independent refolding pathways. The buildup of the different unfolded species upon unfolding of the protein from the native state was monitored by absorbance using double-jump experiments. These experiments were carried out at 15 degrees C and consisted of an unfolding step at 4.2 M GdnHCl and pH 2.0, followed, after a variable delay time, by a refolding step at 0.58 M GdnHCl and pH 5.0. The results of these experiments support the conclusion that the different unfolded species arise from cis-trans isomerizations at the X-Pro peptide bonds of Pro 93, 114, and 117 in the unfolded state of the protein. The rates of these isomerizations were obtained for each of these three X-Pro peptide bonds at 15 degrees C. | The impact of folding funnels and folding simulations on the way experimentalists interpret results is examined. The image of the transition state has changed from a unique species that has a strained configuration, with a correspondingly high free energy, to a more ordinary folding intermediate, whose balance between limited conformational entropy and stabilizing contacts places it at the top of the free energy barrier. Evidence for a broad transition barrier comes from studies showing that mutations can change the position of the barrier. The main controversial issue now is whether populated folding intermediates are productive on-pathway intermediates or dead-end traps. Direct experimental evidence is needed. Theories suggesting that populated intermediates are trapped in a glasslike state are usually based on mechanisms which imply that trapping would only be extremely short-lived (e.g., nanoseconds) in water at 25 degrees C. There seems to be little experimental evidence for long-lived trapping in monomers, if folding aggregates are excluded. On the other hand, there is good evidence for kinetic trapping in dimers. alpha-Helix formation is currently the fastest known process in protein folding, and incipient helices are present at the start of folding. Fast helix formation has the effect of narrowing drastically the choice of folding routes. Thus helix formation can direct folding. It changes the folding metaphor from pouring liquid down a folding funnel to a train leaving a switchyard with only a few choices of exit tracks. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,227 |
Derivatives of the self-complementary 2-guanidiniocarbonyl pyrrole 5-carboxylate zwitterion (1) (previously reported by us to dimerize to 1•1 with an aggregation constant of ca. >10(10) M(-l) in DMSO) aggregate in a diverse manner depending on, e.g., variation of concentration or its protonation state. The mode of aggregation was analyzed by spectroscopic (NMR, UV) and microscopic (AFM, SEM, HIM, and TEM) methods. Aggregation of dimers of these zwitterions to higher supramolecular structures was achieved by introduction of sec-amide substituents at the 3-position, i.e., at the rearward periphery of the parent binding motif. A butyl amide substituent as in 2b enables the discoid dimers to further aggregate into one-dimensional (rod-like) stacks. Quantitative UV dilution studies showed that this aggregation is strongly cooperative following a nucleation elongation mechanism. The amide hydrogen seems to be essential for this rod-like aggregation, as neither 1 nor a corresponding tert-amide congener 2a form comparable structures. Therefore, a hydrogen bond-assisted π-π-interaction of the dimeric zwitterions is suggested to promote this aggregation mode, which is further affected by the nature of the amide substituent (e.g., steric demand), enabling the formation of bundles of strands or even two-dimensional sheets. By exploiting the zwitterionic nature of the aggregating discoid dimers, a reversible pH switch was realized: dimerization of all compounds is suppressed by protonation of the carboxylate moiety, converting the zwitterions into typical cationic amphiphiles. Accordingly, typical nanostructures like vesicles, tubes, and flat sheets are formed reversibly under acidic conditions, which reassemble into the original rod-like aggregates upon readjustment to neutral pH. | We report fabrication, characterization, and potential applications of polyoxometalate (POM)/ionic liquid (IL) supramolecular spheres in water for the first time. These supramolecular spheres have highly ordered structures and show excellent reversible self-assembly and tunable photoluminescence properties, which can be manipulated by adjusting pH of the aqueous solution. Specifically, the formation of POM/IL supramolecular spheres results in quenching of fluorescence emitted by Eu-POM because hopping of the d1 electron in the POM molecule is blocked by hydrogen bond existing between the oxygen atom of POM and the carboxylic acid group of IL. However, the fluorescence can be completely recovered by gradually increasing pH of the aqueous solution due to the pH-induced deprotonation of the carboxylic acid group of IL, which results in disassembly of the fabricated supramolecular spheres. Applications of these stimuli-responsive photoluminescent POM-based supramolecular materials are demonstrated in biological media. Dual signaling responses of turbidity and fluorescence are observed simultaneously in the detection of urease and heavy metals based on pH-induced disassembly of the supramolecular spheres during the biochemical events in aqueous solution. In addition, guest molecules are encapsulated into the supramolecular spheres, and controlled release of these entrapped molecules is demonstrated in the presence of external stimuli. This study shows potential of stimuli-responsive POM/IL supramolecular materials in biological applications. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,228 |
Aim of the present investigation is to broaden an understanding of the interactions between imidazolium based cationic surface active ionic liquid (SAIL) 1-dodecyl-3-methylimidazolium bromide [C12mim][Br] and an anionic polyelectrolyte poly(4-styrenesufonic acid-co-maleic acid) sodium salt (PSSA-co-MA) in aqueous media by using fluorimetry, conductometry and tensiometry techniques. The various states of interaction and critical micelle concentration (cmc) have been reviewed due to the strong hydrophobic and electrostatic interactions. Also degree of ionization, α, cmc and various thermodynamic parameters were determined by conductivity measurement in the temperature range 298.15–318.15 K. The surface tension curve displays the presence of pronounced knap in the surface tension at SAIL concentrations below cmc of the SAIL. The various surface parameters are calculated from surface tension measurement. Aggregation number (Nagg) and cmc were determined by fluorimetric measurements at temperature 298 K. In all cases it was observed that the cmc values were decreased with increase in the concentration of polyelectrolyte this is attributed to the strong electrostatic interactions between SAIL and polyelectrolyte. Also the aggregation behaviour of SAIL begins shifting from entropy-driven to enthalpy-driven with increasing the concentration of polyelectrolyte and increase in temperature. The results obtained from different measurements are in good agreement with each other. | Four dodecyl sulfate-based anionic surface-active ionic liquids were synthesized. Physicochemical parameters of surface-active ionic liquids (SAILs) or SAIL/gelatin aqueous solutions were demonstrated. Critical micelle concentration (cmc) values of [Emim][C12H25SO4], [Amim][C12H25SO4], [Bmim][C12H25SO4], and [Etmim][C12H25SO4] were 2.10 mmol/L, 1.95 mmol/L, 0.95 mmol/L, and 0.86 mmol/L at 298.15 K, respectively. cmc values of four SAILs followed the decreasing trend: [Emim][C12H25SO4] ≈ [Amim][C12H25SO4] > [Bmim][C12H25SO4] ≈ [Etmim][C12H25SO4]. The alkyl chain length (ethyl to butyl group) and electron absorption effect (carboxylate ester or allyl group) of substituent in cationic imidazolium groups played important role in micelle formation of SAILs. cmc values of SAIL/gelatin aqueous solutions were lower than those of SAILs. Micelle formation (SAIL or SAIL/gelatin) was spontaneous, exothermic, and entropy-driven. From DFT calculation, typical hydrogen bonds were found between active hydrogen atom of imidazole ring and oxygen, sulfur atoms of sulfate anion group. The information obtained would provide guide for design and synthesis of novel SAILs for wide gelatin application. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,229 |
Nanopores enable the sensing of individual molecules based on the temporary blockades in ionic pore current. Initially conducted a decade ago with a biological protein pore, electrical recordings are now routinely performed with synthetic pores sculptured into polymeric and inorganic membranes. Assisted by channel engineering, the range of analytes has been expanded from nucleic acids to peptides, proteins, organic polymers, and small molecules. Apart from being an attractive analytical approach, nanopore recording has developed into a general platform technology with which it is possible to examine the biophysics, physicochemistry, and chemistry of individual molecules. Nanopores can also be exploited for separation technologies and nanofluidics due to their ability to control the flow of solvated ions. The combined use with atomic force and fluorescence microscopy is extending the versatility of nanopores for single-molecule research. | Many fundamental biological processes involve moving macromolecules across membranes, through nanopores, in a process called translocation. Such motion is necessary for gene expression and regulation, tissue formation, and viral infection. Furthermore, in recent years nanopore technologies have been developed for single molecule detection of biological and synthetic macromolecules, which have been most notably employed in next generation DNA sequencing devices. Many successful theories have been established, which calculate the entropic barrier required to elongate a chain during translocation. However, these theories are at the level of the translocation coordinate (number of forward steps) and thus lack a clear connection to experiments and simulations. Furthermore, the proper diffusion coefficient for such a coordinate is unclear. In order to address these issues, we propose a center of mass (CM) theory for translocation. We start with the entropic barrier approach and show that the translocation coordinate is equivalent to the center of mass of the chain, providing a direct interpretation of previous theoretical studies. We thus recognize that the appropriate dynamics is given by CM diffusion, and calculate the appropriate diffusion constant (Rouse or Zimm) as the chain translocates. We illustrate our theoretical approach with a planar nanopore geometry and calculate some characteristic dynamical predictions. Our main result is the connection between the translocation coordinate and the chain CM, however, we also find that the translocation time is sped up by 1–2 orders of magnitude if hydrodynamic interactions are present. Our approach can be extended to include the details included in previous translocation theories. Most importantly this work provides a direct connection between theoretical approaches and experiments or simulations. SIGNIFICANCE Macromolecule motion through nanopores is critical for many biological processes, and has been recently employed for nucleic acid sequencing. Despite this, direct theoretical understandings of translocation are difficult to evaluate due to the introduction of the translocation coordinate. In this manuscript, we propose a theory for translocation written at the center of mass level of the polymer chain. This theoretical approach is more easily compared to experimental and simulation results, and additionally allows one to accurately account for hydrodynamic interactions on the macromolecule dynamics. | Background ::: Serum calcium (Ca) and inorganic phosphate (Pi) concentrations and calcium-phosphate product (CPP) levels are positively associated with worse outcomes in patients with chronic kidney disease, but there are few data for Pi or Ca and none for CPP in patients with chronic heart failure (CHF). | eng_Latn | 26,230 |
The mechanical properties for silica hydrogel prepared at physiological conditions are reported in this paper. The mechanical testing was performed in the compression mode determining the mechanical characteristics as a function of aging time in TRIS buffer up to 14 days. In addition to a typically used gradient method for Young’s modulus determination from the stress–strain curves, a new phenomenological model was proposed to describe the experimental data. The mechanical properties were stabilized after 2 days of aging, which was concluded from an increase in Young’s modulus between 90 and 400 kPa, an increase in stress at break between 50 and 100 kPa and by a decrease in relative deformation at break from 0.26 to 0.16. The height of samples was constant in the first three days of aging followed by a decrease by ~20%. Dissolving of silica hydrogel characterized through determination of silica content in TRIS buffer employing the molybdenum method was not found to be responsible for this phenomenon. The phenomenological model is proposed to be used for a reliable evaluation of mechanical properties of silica as well as other hydrogels exhibiting low Young’s modulus. | Whole cells encapsulated in silica gels are usedin a wide variety of applications in biomedicine, biotech-nology and bioremediation. Drying after encapsulation isdesirable to enhance the strength of the gel and to make itlighter, facilitating its use, storage and transportation.However, preserving biological activity of the cells in adesiccated state remains a formidable challenge. In thisstudy, different drying conditions for a silica gel-encap-sulated bacterial biocatalyst (atrazine biodegradingEscherichia coli) were studied to enhance mechanicalproperties while sustaining long-term biocatalytic activityof the bacteria. Effects of lyoprotectant solutions contain-ing 0.4 M sucrose, 0.4 M trehalose or 30 % (wt/wt) glyc-erol on the activity of the encapsulated bacteria duringdrying were investigated. It was determined that two ordersof magnitude increase in the elastic modulus (E) and thecompressive stress at failure (r) of the gel could beachieved by drying, independent of the drying rate. It wasshown that partially desiccated silica gels preserved andenhanced the biocatalytic activity of the encapsulatedbacteria up to a critical drying level. Atrazine biodegra-dation activity of encapsulated bacteria suspended with0.4 M sucrose and PBS increased with increasing waterremoval, reaching a maximum at 68 % water loss. Thisenhanced activity was sustained for 3 months, when thegels were stored at 4 C.Graphical Keywords Bioencapsulation Bioremediation Biocatalysis Atrazine Silica gel Desiccation | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,231 |
Hierarchical TiO2 nanostructures with the nanograss at the top and the close-ended nanotube at the bottom were synthesized by an extended electrochemical anodization process. Upon thermal annealing, the hierarchical TiO2 nanostructures exhibit a morphology-dependent phase transformation behavior: the amorphous as-prepared nanotube layer undergoes an amorphous-anatase-rutile phase transformation upon annealing at 550 °C and 850 °C, respectively; the nanograss, on the other hand, remains in the anatase phase with an annealing temperature up to 850 °C and becomes anatase-dominant anatase–rutile-multiphase at 900 °C. In addition, the nanotube and nanograss exhibit intriguing light-emitting properties. A two-dimensional X-ray absorption near-edge structure – X-ray excited optical luminescence (2D XANES–XEOL) spectroscopy technique is used to investigate such phenomenon, which correlates the origin of the luminescence with the local chemical entrainment of the nanostructured TiO2. Implications of these observat... | A black TiO2 nanotube (NT) heterostructure with an anatase-core and an amorphous-shell has been synthesized by NH3 annealing of amorphous NT grown by the anodization of a Ti substrate. Remarkable photoabsorption behavior of these black TiO2 NTs is observed: strong absorption throughout the entire optical wavelength region from ultraviolet to near-infrared. X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS) and resonant inelastic X-ray scattering (RIXS) have been used to elucidate the origin of this spectacular light capture phenomenon. Surface-sensitive XANES recorded in total electron yield and XPS show that the surface layer is amorphous with a chemical composition approaching that of Ti4O7. Bulk-sensitive XANES using X-ray partial fluorescence yield and Ti 2p RIXS confirm the presence of a rich amount of Ti3+ in the crystalline bulk (core of the NT with anatase structure) of black TiO2 NTs, which exhibits a dispersive d-d energy loss at ∼2 eV corresponding to the broad... | Three unrelated enzymes (ribonuclease, chymotrypsin, and lysozyme) display markedly enhanced thermostability in anhydrous organic solvents compared to that in aqueous solution. At 110-145 degrees C in nonaqueous media all three enzymes inactivate due to heat-induced protein aggregation, as determined by gel filtration chromatography. Using bovine pancreatic ribonuclease A as a model, it has been established that enzymes are much more thermostable in hydrophobic solvents (shown to be essentially inert with respect to their interaction with the protein) than in hydrophilic ones (shown to strip water from the enzyme). The heat-induced aggregates of ribonuclease were characterized as both physically associated and chemically crosslinked protein agglomerates, with the latter being in part due to transamidation and intermolecular disulfide interchange reactions. The thermal denaturation of ribonuclease in neat organic solvents has been examined by means of differential scanning calorimetry. In hydrophobic solvents, the enzyme exhibits greatly enhanced thermal denaturation temperatures (T(m) values as high as 124 degrees C) compared to aqueous solution. The thermostability of ribonuclease towards heat-induced denaturation and aggregation decreases as the water content of the protein powder increases. The experimental data obtained suggest that enzymes are extremely thermostable in anhydrous organic solvents due to their conformational rigidity in the dehydrated state and their resistance to nearly all the covalent reactions causing irreversible thermoinactivation of enzymes in aqueous solution. | eng_Latn | 26,232 |
Silica flocculated with a high molecular weight poly(DMVPMS) contains aggregates that are stable enough to permit size measurement with a Coulter counter. The average size of these aggregates increases up to a critical level of added polymer; the primary particles reappear at higher levels of added polymer. The aggregate size is reduced by continued mixing and the particle size distribution before flocculation is approached. Subsidence rates, equilibrium sediment volumes, and refiltration rates give somewhat different estimates of the degree of flocculation. Additional aggregation beyond that measured by the Coulter counter must be considered in the interpretation of these data. The decrease in floc strength during continued agitation is attributed to a disaggregation of the bridging polymer, to a decrease in the interparticle bonding of the bridging polymer, and to an increase in the surface coverage with polymer. | In this work, the P4VP was synthesized by radical polymerization. The quaternization of this polymer by octyl bromide leads to the two copolymers [poly(N-octyl-4-vinylpyridinium bromide] named P4VPC8Br 48.8% and P4VPC8Br 72%. The thermodynamic behavior associated with the potentiometric titration of the copolymers, was reported in the temperature range (293.16–333.16 K) and as a function of the concentrations (0.25×10−4 mmol/dm3 12.3×10−4 mmol/dm3). The free energy of dissociation ΔGdiss variation versus the neutralization degree shows the negative value due to the steric and electrostatic effect of the alkyl chains. The positive values of ΔH and ΔS confirmed the spontaneity and disorder of the reaction. The critical concentration C* of the two copolymers was determined from the enthalpy ΔH0 and entropy ΔS0 changes. The transition in conformation of the copolymer chains was influenced by the presence of hydrophobic-hydrophilic and hydrophobic-hydrophobic interactions. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,233 |
The structure of 3 nm ZnS nanoparticles differs from that of bulk ZnS and is shown to vary with the particle aggregation state. Dispersed or weakly aggregated nanoparticles in suspension have a more distorted internal structure than strongly aggregated nanoparticles. Reversible switching between distorted and crystalline structures can be induced by changing the aggregation state via slow drying and ultrasonic agitation. The transformation was analyzed using pair distribution function data from wide angle x-ray diffraction and the aggregation state monitored via small angle x-ray scattering. Molecular modeling provides insight into particle-particle interactions that induce the structural changes. The reversible nature also implies a low activation energy of nanoparticle transformation and indicates that distorted nanoparticles are not trapped in a metastable state. | Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. The particles involved in these nonclassical pathways to crystallization are diverse, in contrast to classical models that consider only the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle-attachment processes and show that multiple pathways result from the interplay of free-energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects, particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemble behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems, biominerals, and patterns of mineralization in natural environments. | ABSTRACTUNC-45A is an ubiquitously expressed protein highly conserved throughout evolution. Most of what we currently know about UNC-45A pertains to its role as a regulator of the actomyosin system... | eng_Latn | 26,234 |
Aquaporins are important and well-studied water channel membrane proteins. However, being membrane proteins, sample preparation for functional analysis is tedious and time-consuming. In this paper, we report a new approach for the co-translational insertion of two aquaporins from Escherichia coli and Nicotiana tabacum using the CFPS system. This was done in the presence of liposomes with a modified procedure to form homogenous proteo-liposomes suitable for functional analysis of water permeability using stopped-flow spectrophotometry. Two model aquaporins, AqpZ and NtPIP2;1, were successfully incorporated into the liposome in their active forms. Shifted green fluorescent protein was fused to the C-terminal part of AqpZ to monitor its insertion and status in the lipid environment. This new fast approach offers a fast and straightforward method for the functional analysis of aquaporins in both prokaryotic and eukaryotic organisms. | The efficiency of reconstitution of the lactose transport protein (LacS) of Streptococcus thermophilus is markedly higher with Triton X-100 than with other detergents commonly employed to mediate the membrane insertion. To rationalize these differences, the lipid/detergent structures that are formed in the reconstitution process were studied by cryotransmission electron microscopy. Surprisingly, the two nonionic detergents Triton X-100 and n-dodecyl β-d-maltoside (DDM) affected the liposome structures in a completely different manner. Preformed liposomes titrated with Triton X-100 maintained their bilayer structure far beyond the onset of solubilization, and transport activity was maximal when LacS was inserted into these structures. With DDM the vesicular structures were already disrupted at the onset of solubilization and these membrane sheets were converted into long threadlike micelles at higher DDM to lipid ratios. Triton X-100 allowed the protein to be reconstituted with the hydrophilic surface expo... | There is strong evidence that aquaporins are central components in plant water relations. Plant species possess more aquaporin genes than species from other kingdoms. According to sequence similarities, four major groups have been identified, which can be further divided into subgroups that may correspond to localization and transport selectivity. They may be involved in compatible solute distribution, gas-transfer (CO2, NH3) as well as in micronutrient uptake (boric acid). Recent advances in determining the structure of some aquaporins gives further details on the mechanism of selectivity. Gating behaviour of aquaporins is poorly understood but evidence is mounting that phosphorylation, pH, pCa and osmotic gradients can affect water channel activity. Aquaporins are enriched in zones of fast cell division and expansion, or in areas where water flow or solute flux density would be expected to be high. This includes biotrophic interfaces between plants and parasites, between plants and symbiotic bacteria or fungi, and between germinating pollen and stigma. On a cellular level aquaporin clusters have been identified in some membranes. There is also a possibility that aquaporins in the endoplasmic reticulum may function in symplasmic transport if water can flow from cell to cell via the desmotubules in plasmodesmata. Functional characterization of aquaporins in the native membrane has raised doubt about the conclusiveness of expression patterns alone and need to be conducted in parallel. The challenge will be to elucidate gating on a molecular level and cellular level and to tie those findings into plant water relations on a macroscopic scale where various flow pathways need to be considered. | eng_Latn | 26,235 |
The self-assembly behavior and structural characteristics of the block ionomer complexes from poly(styrene)-block-poly(N-ethyl-4-vinylpyridinium) (PS-b-PE4VP) cations and bis(2-ethylhexyl) sulfosuccinate (AOT) anions in nonpolar solvents were examined by turbidity, viscometry, sedimentation velocity, isothermal diffusion, and dynamic light scattering techniques. The complexes were synthesized by reacting PS-b-PE4VP with AOT in aqueous media. The resulting water-insoluble materials contained PS block and PE4VP/AOT complex block. The length of PS block was constant and equal to 100 units, while the length of PE4VP/AOT block was varied (100−500 units). These complexes dissolved in hexane upon addition of small amounts (0.5−10 vol %) of aliphatic alcohols and formed stable dispersions with the size of the particles varying from 50 to 95 nm. The particles represented micelle-like aggregates of PS-b-PE4VP/AOT complexes with the core formed by PS chains and the shell formed by PE4VP chains electrostatically boun... | The aggregation of cationic block copolymers formed by polystyrene (PS) and poly(ethyl-4-vinylpyridine) (PS-b-PE4VP) was studied in aqueous solution. Diblock copolymers of PS and poly(4-vinylpyridine) were synthesized by sequential anionic polymerization using BuLi as initiator. Subsequently, the 4-vinylpyridine units were quaternized with ethyl bromide to obtain cationic PS-b-PE4VP block copolymers with different quaternization degree. The self-aggregation of cationic block copolymers was studied by fluorescence probing, whereas the morphology and size of polymer micelles were determined by transmission electronic microscopy. Results indicate that spherical micelles with sizes lower than 100 nm were formed, whereas their micropolarity decreases with increasing quaternization degree. The partition of phenols between the micellar and aqueous phase was studied by using the pseudo-phase model, and the results show that the partition coefficients increase with increasing length of the side alkyl chain and are larger for star micelles. These results are discussed in terms of three-region model. | ABSTRACTUNC-45A is an ubiquitously expressed protein highly conserved throughout evolution. Most of what we currently know about UNC-45A pertains to its role as a regulator of the actomyosin system... | eng_Latn | 26,236 |
We show for the oppositely charged system poly(diallyldimethylammonium chloride)/sodium dodecyl sulfate that the cliff edge peak in its surface tension isotherm results from the comprehensive precipitation of bulk complexes into sediment, leaving a supernatant that is virtually transparent and a depleted adsorption layer at the air/water interface. The aggregation and settling processes take about 3 days to reach completion and occur at bulk compositions around charge neutrality of the complexes which lack long-term colloidal stability. We demonstrate excellent quantitative agreement between the measured surface tension values and a peak calculated from the surface excess of surfactant in the precipitation region measured by neutron reflectometry, using the approximation that there is no polymer left in the liquid phase. The nonequilibrium nature of the system is emphasized by the production of very different interfacial properties from equivalent aged samples that are handled differently. We go on to outline our perspective on the "true equilibrium" state of this intriguing system and conclude with a comment on its practical relevance given that the interfacial properties can be so readily influenced by the handling of kinetically trapped bulk aggregates. | Solutions of surfactant–polymer mixtures often exhibit different foaming properties, compared to the solutions of the individual components, due to the strong tendency for formation of polymer–surfactant complexes in the bulk and on the surface of the mixed solutions. A generally shared view in the literature is that electrostatic interactions govern the formation of these complexes, for example between anionic surfactants and cationic polymers. In this study we combine foam tests with model experiments to evaluate and explain the effect of several polymer–surfactant mixtures on the foaminess and foam stability of the respective solutions. Anionic, cationic, and nonionic surfactants (SDS, C12TAB, and C12EO23) were studied to clarify the role of surfactant charge. Highly hydrophilic cationic and nonionic polymers (polyvinylamine and polyvinylformamide, respectivey) were chosen to eliminate the (more trivial) effect of direct hydrophobic interactions between the surfactant tails and the hydrophobic regions ... | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,237 |
The structure of the soluble Rieske protein from Thermus thermophilus has been determined at a resolution of 1.3 A at pH 8.5 using multiwavelength anomalous dispersion (MAD) techniques. This is the first report of a Rieske protein from a menaquinone-utilizing organism. The structure shows an overall fold similar to previously reported Rieske proteins. A novel feature of this crystal form appears to be a shared hydrogen between the His-134 imidazole ring ligated to Fe2 of the [2Fe−2S] cluster and its symmetry partner, His-134‘, one being formally an imidazolate anion, Fe2-(His-134)Ne-···H-Ne‘(His-134‘)-Fe2‘, in which crystallographic C2 axes pass equidistant between Ne···Ne‘ and normal to the line defined by Ne···Ne‘. This provides evidence for a stable, oxidized cluster with a His- ligand and lends support to a previously proposed mechanism of coupled proton and electron transfer. A detailed comparison of the Thermus Rieske protein with six other Rieske and Rieske-type proteins indicates: (a) The cluster... | Iron-sulfur clusters (ISC) ([Fe-S]) are evolutionarily ancient and ubiquitous inorganic prosthetic groups present in almost all living organisms, whose biosynthetic assembly is dependent on complex protein machineries. [Fe-S] clusters are involved in biologically important processes, ranging from electron transfer catalysis to transcriptional regulatory roles. Three different systems involved in [Fe-S] cluster assembly have already been characterized in Proteobacteria, namely, the nitrogen fixation system, the ISC system and the sulfur assimilation system. Although they are well described in various microorganisms, these machineries are poorly characterized in members of the Firmicutes phylum, to which several groups of pathogenic bacteria belong. Recently, several research groups have made efforts to elucidate the biogenesis of [Fe-S] clusters at the molecular level in Firmicutes, and many important characteristics have been described. Considering the pivotal role of [Fe-S] clusters in a number of biological processes, the review presented here focuses on the description of the biosynthetic machineries for [Fe-S] cluster biogenesis in prokaryotes, followed by a discussion on recent results observed for Firmicutes [Fe-S] cluster assembly. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 26,238 |
We have synthesized iron nanoclusters using two chemical types of inverse micelle systems to control the growth process. Surprisingly, we have found that the phase of the resulting nanosize iron depends strongly on the chemical nature of the surfactant used during the growth of the clusters. For example, use of nonionic surfactant micelles for this room-temperature synthesis produces the normally-high-temperature γ-phase with a fcc structure as determined by selected area electron diffraction (SAD) and high-resolution lattice fringe images. Use of a cationic quaternary ammonium surfactant micelle system, on the other hand, produces the normal bcc α-iron phase as determined by SAD. This strong dependence of the structure of nanosize clusters on surfactant type may reflect different binding-site preferences for the chemically different surfactants during the growth stage of the cluster synthesis. This is analogous to the well-known role of surfactants as habit modifiers during macroscopic crystalline growth... | The addition of superparamagnetic iron nanoparticles into polystyrene matrix allows for the modification of the physical properties as well as the implementation of new features in the hybrid nanomaterials. These materials have excellent potential for biomedical and bioengineering applications. Nevertheless, it is necessary to achieve a good dispersion of magnetic nanoparticles for its successful incorporation into polymer particles. This can be obtained through the use of a stabilizer, which provides stability against aggregation. In this work, magnetic nanoparticles were dispersed using different stabilizers. Subsequently, ferrofluids stabilized using the mixture of ABEX/IGEPAL and acrylic acid (AA) were used to synthesize PS-Fe3O4 nanocomposites, through miniemulsion and emulsion polymerization conventional techniques. Semicontinuous and batch processes were compared, by varying surfactants and their concentrations. The PS-Fe3O4 nanoparticles were characterized by dynamic light scattering, scanning electron microscopy, Raman spectroscopy, and vibrating sample magnetometer. Magnetic nanoparticle dispersions show better results when the anionic and nonionic surfactants are used as a mixture rather than when used alone. Results of DLS showed that the semicontinuous process allowed obtaining monodisperse materials, whereas polidisperse systems are generated in batch process. Raman spectroscopy confirmed the presence of magnetite and polystyrene in the nanocomposites. PS-Fe3O4 nanoparticles showed superparamagnetic behavior with final magnetization of around 0.01 emu/g and low coercivity, properties that make them suitable for applications in wide fields of technology. Particle size (Dz), was lower than 300 nm in all cases. Moreover, the use of AA as stabilizer allows enhancing the PS-Fe3O4 composite properties. These findings showed that particle size, morphology, and agglomeration are directly influenced by the concentration and the type of surfactant employed. | Antimicrobial cationic peptides are an important component of the innate defenses of all species of life. Different peptides may have antibacterial, antiendotoxic, antibiotic-potentiating or antifungal properties, and so they are being developed for use as a novel class of antimicrobial agents and as the basis for making transgenic disease-resistant plants and animals. | eng_Latn | 26,239 |
External electric fields can induce or prevent liquid swelling and liposome formation on solid surfaces. These effects depend on the type of lipid and surface, the medium parameters (temperature, osmolarity, ionic strength), the dried lipid layer thickness, the type and parameters of the electric field (dc or ac, amplitude, frequency, current), the situation of the lipid (on the very electrode surface or an another surface) and the time of exposure. This paper presents new data and theoretical estimates which allow us to suggest a possible mechanism of liposome electroformation. The new experimental results with negatively charged egg lecithin (EggL−) and neutral synthetic phosphatidylcholine (PC) are that (1) cholesterol in mixtures with EggL− inhibits liposome formation, (2) sodium chloride leads to a decrease in the size and number of liposomes; liposomes do not form in solution more concentrated than 10 mM NaCl, (3) dextran also decreases the size and number of liposomes; they do not form in solution of dextran concentration higher than 2.5 mM, (4) dc electric fields can overcome the effect of dextran and lead to swelling even in 2.5 mM dextran solutions, (5) dc fields are most effective if applied in the first 30 s of lipid swelling, the increase of the period of the field action does not lead to a significant effect on the liposome yield, (6) a similar effect was also observed with (PC), but the critical period of time was a bit shorter — 10 s. The balance of forces acting on a lamellae of hydrating lipid shows that a possible pathway of liposome formation can include at least three basic stages: (1) separation of interacting membranes — the hydration and electrostatic interactions yield the main driving forces for this process, (2) instability of bending which can result from negative membrane tension due to surface and line tension and (3) the bending itself and closing of the membranes — the kinetics of this process and the instability of bending largely determine the liposome size distribution. External electric fields can affect any of these stages by at least two mechanisms: (1) direct electrostatic interaction and (2) redistribution of the counter-ions between the membranes. The interplay between the van der Waals, hydration and electrostatic forces is the major determinant of the mechanisms of liposome electroformation. | Antimicrobial peptides (AMPs) are a potential source of new molecules to counter the increase in antimicrobial resistant infections but a better understanding of their properties is required to understand their native function and for effective translation as therapeutics. Details of the mechanism of their interaction with the bacterial plasma membrane are desired since damage or penetration of this structure is considered essential for AMPs activity. Relatively modest modifications to AMPs primary sequence can induce substantial changes in potency and/or spectrum of activity but, hitherto, have not been predicted to substantially alter the mechanism of interaction with the bacterial plasma membrane. Here we use a combination of molecular dynamics simulations, circular dichroism, solid-state NMR and patch clamp to investigate the extent to which temporin B and its analogues can be distinguished both in vitro and in silico on the basis of their interactions with model membranes. Enhancing the hydrophobicity of the N-terminus and cationicity of the C-terminus in temporin B improves its membrane activity and potency against both Gram-negative and Gram-positive bacteria. In contrast, enhancing the cationicity of the N-terminus abrogates its ability to trigger channel conductance and renders it ineffective against Gram-positive bacteria while nevertheless enhancing its potency against Escherichia coli. Our findings suggest even closely related AMPs may target the same bacterium with fundamentally differing mechanisms of action. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,240 |
The parameters used to evaluate biomacromolecular crystal quality [Rmerge, I/σ(I), maximum resolution and mosaicity] strongly depend on the experimental diffraction conditions. In this paper, the distinctive features of the relative Wilson plot method are described and it is shown that the overall B factor obtained from this plot is more appropriate for the characterization of protein crystals. The relative Wilson plot has been applied to the characterization of crystals of the B-DNA decamer d(CCATTAATGG) and crystals of the proteins DsrD (dissimilatory sulfite reductase D) and hen egg-white lysozyme (HEWL), which were studied by neutron diffraction. It was found that the crystal quality of the B-DNA decamer and DsrD depended significantly on the regions of the crystallization phase diagram from which the samples were taken. However, in the case of HEWL crystal quality appears to be independent of the region of the crystallization phase diagram. | Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins, a technique complimentary to ultra-high-resolution [1, 2] X-ray diffraction. Three different types of neutron diffractometers for biological macromolecules have been constructed in Japan, France and the United States, and they have been used to determine the crystal structures of proteins up to resolution limits of 1.5–2.5 A. Results relating to hydrogen positions and hydration patterns in proteins have been obtained from these studies. Examples include the geometrical details of hydrogen bonds, H/D exchange in proteins and oligonucleotides, the role of hydrogen atoms in enzymatic activity and thermostability, and the dynamical behavior of hydration structures, all of which have been extracted from these structural results and reviewed. Other techniques, such as the growth of large single crystals, the preparation of fully deuterated proteins, the use of cryogenic techniques, and a data base of hydrogen and hydration in proteins, will be described. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,241 |
Previous experiments have shown that a fraction of microtubule-associated proteins is essential for the self-assembly of microtubules in vitro . When tubulin was titrated with increasing concentrations of these non-tubulin accessory factors, both the rate and extent of polymerization increased in a sigmoidal as opposed to a stoichiometric fashion. The non-tubulin proteins promoted the nucleation of microtubules as determined from the analysis of the kinetics of tubulin selfassembly and the examination of the microtubule length distribution following polymerization. The effect of the non-tubulin factors on microtubule elongation was determined by kinetic experiments in which purified tubulin subunits were added to microtubule seeds and the initial rate of polymerization was measured under conditions where spontaneous self-assembly was below detectable levels. In addition, microtubule growth was also observed when isolated flagellar axonemes were incubated with purified tubulin subunits indicating that the non-tubulin factors were not an absolute requirement for elongation. Analysis of the data in terms of the condensation mechanism of microtubule assembly indicated that the non-tubulin proteins stimulated the growth of microtubules not by increasing the rate of polymerization but by decreasing the rate of depolyerization. The mechanism by which these accessory factors promote tubulin assembly may be summarized as follows: under the conditions employed, they are required for tubulin initiation but not for elongation; the factors affect the extent and net rate at which polymer is formed by binding to the polymer, thereby stabilizing the formed microtubules and consequently shifting the equilibrium to favor assembly. | We measured the elasticity and viscosity of brain tubulin solutions under various conditions with a cone and plate rheometer using both oscillatory and steady shearing modes. Microtubules composed of purified tubulin, purified tubulin with taxol and 3x cycled microtubule protein from pig, cow, and chicken behaved as mechanically indistinguishable viscoelastic materials. Microtubules composed of pure tubulin and heat stable microtubule-associated proteins were also similar but did not recover their mechanical properties after shearing like other samples, even after 60 min. All of the other microtubule samples were more rigid after flow orientation, suggesting that the mechanical properties of anisotropic arrays of microtubules may be substantially greater than those of randomly arranged microtubules. These experiments confirm that MAPs do not cross link microtubules. Surprisingly, under conditions where microtubule assembly is strongly inhibited (either 5 degrees or at 37 degrees C with colchicine or Ca++) tubulin was mechanically indistinguishable from microtubules at 10-20 microM concentration. By electron microscopy and ultracentrifugation these samples were devoid of microtubules or other obvious structures. However, these mechanical data are strong evidence that tubulin will spontaneously assemble into alternate structures (aggregates) in nonpolymerizing conditions. Because unpolymerized tubulin is found in significant quantities in the cytoplasm, it may contribute significantly to the viscoelastic properties of cytoplasm, especially at low deformation rates. | ABSTRACTUNC-45A is an ubiquitously expressed protein highly conserved throughout evolution. Most of what we currently know about UNC-45A pertains to its role as a regulator of the actomyosin system... | eng_Latn | 26,242 |
The influence of different micro- and nanosized alumina fillers, dispersed in an unsaturated polyester resin as polymer matrix, on the resulting composite flow behaviour was investigated systematically. It was found that the composite viscosity depends strongly on the properties of the applied particles like particle size, particle size distribution, solid load and especially on the specific surface area. The change of the relative viscosity with load can be described by using the different established semiempirical approaches for the estimation of the critical filler load. The value of the latter one decreases with increasing fillers surface area value significantly. The impact of the solid load as well as the fillers specific surface area on composite's flow behaviour will be discussed in the following. | The temperature has a significant influence on the character of flow of polymer suspensions filled with BaTiO3 nanoparticles, changing its viscosity and rheology. The viscous flow of suspensions at lower temperature from 5 to 25°C began at higher activation energy ΔEa1 and the systems were thixotropic, characterized with shear thickening at the initial stage of shearing after breaking of structural bonds between the polymer molecules. Herewith, increased shear stresses caused the enlargement of structural elements through additional flocculation by polymer bridging because of adsorption-desorption of EthCell molecule on BaTiO3 nanoparticles surface. At higher temperatures of 30 – 45 °C the viscous flow of suspensions began at the lower values of ΔEa2 indicating decreasing of leisure EthCell chains sufficient to form transient polymer network. Elevation of the temperature stipulated the predominant contribution of thermal Brownian motion to the character of flow. The mobility of macromolecules segments increased, BaTiO3 nanoparticles became to rotate, making impossible the additional structuring. Hence, the effective hydrodynamic radii of floccules remained constant. Moreover, being thixotropic at lower temperatures, the suspensions were characterized by the increasing of effective radii of floccules throughout the shear thickening region. In turn, rheopexic-thixotropic type of flow was characterized by the constant size of floccules along up-flow curves due to the dominant contribution of rotational Brownian motion. Thus, it is very important to control the temperature regime of processing method when exploitation of polymer suspensions. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,243 |
Aim: To evaluate the efficacy of electrochemically activated solution (ECASOL™) in decontaminating Bacillus anthracis Ames and Vollum 1B spores, with and without changing the source water hardness and final ECASOL™ pH. ::: ::: ::: ::: Methods and Results: Five different ECASOL™ formulations were generated, in which the source water hardness and final ECASOL™ pH were varied, resulting in cases where significant changes in free available chlorine (FAC) and oxidative-reduction potential (ORP) were observed. B. anthracis Ames and Vollum 1B spores were suspended in the various ECASOL™ formulations for 30 min, and decontamination efficacy was determined; calcium hypochlorite [5% high-test hypochlorite (HTH)] was used as a positive control. The five different ECASOL™ formulations yielded mean FAC levels ranging from 305 to 464 ppm, and mean ORP levels ranging from +826 to +1000 mV. Exposure to all the ECASOL™ formulations and 5% HTH resulted in ≥7·0 log reductions in both B. anthracis Ames and Vollum 1B spores. ::: ::: ::: ::: Conclusions: The present testing demonstrated that ECASOL™ with a minimum of c. 300-ppm FAC levels and +800-mV ORP inactivated the B. anthracis spores in suspension, similar to 5% HTH. ::: ::: ::: ::: Significance and Impact of the Study: These results provide information for decontaminating B. anthracis Ames and Vollum 1B spores in suspension using ECASOL™. | The study of biofilms has skyrocketed in recent years due to increased awareness of the pervasiveness and impact of biofilms. It costs the USA literally billions of dollars every year in energy losses, equipment damage, product contamination and medical infections. But biofilms also offer huge potential for cleaning up hazardous waste sites, filtering municipal and industrial water and wastewater, and forming biobarriers to protect soil and groundwater from contamination. The complexity of biofilm activity and behavior requires research contributions from many disciplines such as biochemistry, engineering, mathematics and microbiology. The aim of this review is to provide a comprehensive analysis of emerging novel antimicrobial techniques, including those using myriad organic and inorganic products as well as genetic engineering techniques, the use of coordination complex molecules, composite materials and antimicrobial peptides and the use of lasers as such or their modified use in combination treatments. This review also addresses advanced and recent modifications, including methodological changes, and biocide efficacy enhancing strategies. This review will provide future planners of biofilm control technologies with a broad understanding and perspective on the use of biocides in the field of green developments for a sustainable future. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,244 |
We present theoretical studies of peptide amphiphile nanostructures created by Stupp and co-workers [Hartgerink, J. D.; Beniash, E.; Stupp, S. I. Science 2001, 294, 1684] and show that these amphiphiles exhibit attractive electrostatic interactions between their hydrophilic headgroups. These interactions prevail in their competition with the hydrophobic attraction between the amphiphile “tails” for the shape of the self-assembly, leading to cylindrical micelles of nanoscale dimension. The theory is supported by Monte Carlo simulations which show that in the absence of the directional electrostatic interactions between the headgroups the amphiphiles self-assemble into spherical micelles, in accord with our recent formal calculations [Tsonchev, S.; Schatz, G. C.; Ratner, M. A. Nano Lett. 2003, 3, 623], whereas inclusion of the electrostatic interactions leads to cylindrical nanostructures. | Stimuli-responsive, self-assembling nanomaterials hold a great promise to revolutionize medicine and technology. However, current discovery is slow and often serendipitous. Here we report a multiscale modeling study to elucidate the pH-controlled self-assembly of nanofibers from the peptide amphiphiles, palmitoyl-I-A3E4-NH2. The coarse-grained simulations revealed the formation of random-coil based spherical micelles at strong electrostatic repulsion. However, at weak or no electrostatic repulsion, the micelles merge into a nanofiber driven by the β-sheet formation between the peptide segments. The all-atom constant pH molecular dynamics revealed a cooperative transition between random coil and β-sheet in the pH range 6–7, matching the CD data. Interestingly, although the bulk pKa is more than one unit below the transition pH, consistent with the titration data, the highest pKa’s coincide with the transition pH, suggesting that the latter may be tuned by modulating the pKa’s of a few solvent-buried Glu si... | This is the report of 14-year-old boy with a malignant mesothelioma of the tunica vaginalis contained in an abdominoscrotal hydrocele. A review of the literature shows that this aggressive tumor is very rare and has been reported only in adults. | eng_Latn | 26,245 |
Study of integral membrane proteins is of great importance for the understanding of cellular mechanisms, such as photosynthesis, respiration, or bacterial resistance to antibiotics. Those highly hydrophobic proteins are water insoluble; surfactants are thus necessary for their handling in aqueous solutions. Among surfactants recently developed for this use, amphiphilic polymers called amphipols display interesting potential. Amphiphilic biopolymers with similar properties would be particularly attractive. Therefore, we tried to develop hydrophobically-modified polysaccharides able to extract integral membrane proteins and to make them soluble, under non-denaturing conditions. Pullulan is a water-soluble, flexible polysaccharide. Its chemical modification is well controlled. A set of amphiphilic pullulan derivatives with moderate molar mass ( " 30 000 g. Mol-1) was prepared. Carboxymethyl groups were first introduced (0,2 to 1,2 per anhydroglucose unit) to favor water-solubility of amphiphilic derivatives. Large extents (up to 48%) of alkyl (C8 to C12) and 3-phenylpropyl hydrophobic chains were then grafted through amide or ester linkages. Amphiphilic carboxymethylpullulans display surface-active properties. Hydrophobic microdomain formation was evidenced in aqueous solution. According to the samples studied, various aggregation phenomena were observed. Some amphiphilic carboxymethylpullulans are actually able to extract membrane proteins from their lipid surrounding. Comparison of their capacities led to identify C4?18C10d (pullulan with 18% decyl groups and 91% ungrafted carboxymethyl groups) as the most efficient sample. The effect of this amphiphilic biopolymer on protein activity is similar to that of a mild detergent | Membrane proteins classically are handled in aqueous solutions as complexes with detergents. The dissociating character of detergents, combined with the need to maintain an excess of them, frequently results in more or less rapid inactivation of the protein under study. Over the past few years, we have endeavored to develop a novel family of surfactants, dubbed amphipols (APs). APs are amphiphilic polymers that bind to the transmembrane surface of the protein in a noncovalent but, in the absence of a competing surfactant, quasi-irreversible manner. Membrane proteins complexed by APs are in their native state, stable, and they remain water-soluble in the absence of detergent or free APs. An update is presented of the current knowledge about these compounds and their demonstrated or putative uses in membrane biology. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,246 |
The potential of mean force between interstitial solute molecules in Ben-Naim's one-dimensional, many-state lattice model (related to the one-dimensional q-state Potts model) is calculated. Since the model is exactly soluble, all results are explicit and analytic. It is found that the magnitude of the effective attractive force between solutes and the range of that attraction vary inversely with each other: the strength of the attraction, as expected, increases with increasing magnitude of the (entropically unfavorable) free energy of “hydrogen-bond’' formation, but at the same time the range decreases. Conversely, when the unfavourable entropy and favourable energy of “hydrogen-bond’' formation are nearly in balance, the attraction between hydrophobes, while then weak, is of very long range. It is remarked that solubility in a one-dimensional solution model, when the direct intermolecular interactions are of short range, can only be defined osmotically. The solubility of the hydrophobe, as so defined, is calculated with the present model. It is found to decrease with increasing temperature, as expected for a hydrophobic solute. | This paper reports a morphological transition of the spherical colloidal structures of the sodium dodecyl sulfate-polyethylene-bpolyethylene glycol (SDS-PE-b-PEG) complex and anionic micelle (SDS) to ‘‘rod-shaped’’ colloidal structures induced by a charge transfer dye, 1,8-naphthalimide (NAPMD) (forms anions in aqueous solution by intermolecular charge transfer). The distinct steady-state results of NAPMD in the above two media point toward the formation of a new microenvironment. SDS and SDS-PE-b-PEG form unilamellar (ULV) and multilamellar vesicles (MLV), respectively, along with the rod-shaped colloidal structures as observed from transmission electron microscopy (TEM) images. This dye causes a variation in the hydrophilic ⁄ hydrophobic ratio and forms a hydrogen bond with the copolymer in the SDS-PE-b-PEG complex and subjected to electrostatic interaction with the SDS micelle in aqueous solution, which causes this morphological transformation. These vesicles show complete encapsulation of a hydrophobic dye in its interior as evident from the TEM images. ULV get ruptured at low pH, pointing toward their lower stability over MLV at low pH value. The formation of these vesicles with complete idea of its mechanism, encapsulation of bioactive molecules and its rupture at lower pH raise hope as a potential nanoscale vehicle for biologically relevant compounds and their release at low pH medium. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,247 |
Turbidity and light scattering measurements, along with phase contrast microscopy, were used to follow the processes leading to coacervation when aqueous solutions of bovine serum albumin (BSA) and poly-(dimethyldiallylammonium chloride) (PDADMAC) were brought from pH = 4 to 10. The state of macromolecular assembly of complexes formed between BSA and PDADMAC prior to and during the pH-induced coacervation could be characterized by specific pH values at which recognizable transitions took place. In addition to the two characteristic pH values (pHcrit and pH phi) previously identified through turbidimetry, other transitions were explicitly established. On the basis of the pH-induced evolution of scattering intensity measurements, we concluded that the formation of soluble primary protein-polymer complexes is initiated at pHcrit and proceeds until "pH'crit". A subsequent increase in scattering intensity at "pHpre" may arise from the assembly of quasi-neutralized primary complexes as their net positive charge decreases with increase in pH. Subsequently, a maximum in scattering intensity at pH phi is observed coincident with the appearance of turbidity and also corresponding to the first microscopic observation of coacervate droplets. The temperature independence of pHcrit and pH phi suggests that hydrophobic contributions are negligible for the initial BSA-PDADMAC interactions and the subsequent coacervation process. The pH dependence of scattering intensity profiles allowed the identification of two other transitions beyond pH phi. Spherical microcoacervate droplets first observed around pH phi subsequently displayed morphological changes at "pHmorph", followed by the transformation to solid or flocculant substances at pHprecip. | In this work, nanoparticles of chitosan embedded with 25% (w/w) of iron oxide magnetic nanoparticles (magnetite/maghemite) with narrow size-distribution and with a loading efficiency of about 80% for 5-hydroxytryptophan (5-HTP), which is a chemical precursor in the biosynthesis of important neurotransmitters as serotonin, were synthesized with an initial mass ratio of 5-HTP/magnetic chitosan=1.2, using homogeneous precipitation by urea decomposition, in an efficient one-step procedure. Characterization of morphology, structure and surface were performed by XRD, TEM, FTIR, TGA, magnetization and zeta potential measurements, while drug loading and drug releasing were investigated using UV–vis spectroscopy. Kinetic drug release experiments under different pH conditions revealed a pH-sensitivecontrolled-release system, ruled by polymer swelling and/or particle dissolution. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,248 |
A liquid crystal system was used for the fabrication of a highly ordered composite material from genetically engineered M13 bacteriophage and zinc sulfide (ZnS) nanocrystals. The bacteriophage, which formed the basis of the self-ordering system, were selected to have a specific recognition moiety for ZnS crystal surfaces. The bacteriophage were coupled with ZnS solution precursors and spontaneously evolved a self-supporting hybrid film material that was ordered at the nanoscale and at the micrometer scale into ∼ 72-micrometer domains, which were continuous over a centimeter length scale. In addition, suspensions were prepared in which the lyotropic liquid crystalline phase behavior of the hybrid material was controlled by solvent concentration and by the use of a magnetic field. | Free-Standing Films-Basic Physical Notions and Properties. Experimental Techniques. Thinning, Stratification and Rupture. Orientational and Phase Transitions. The Field-Induced Effects. Structure and Defects of Stable Thin Films. Different Applications of Free-Standing Liquid Crystalline Films. Index. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 26,249 |
Hydrogenation of some derivatives of dimethoxytetrahydrofuran in the presence of homogeneous catalysts | 1. ::: ::: Iso-(4, 5, 6, 7-tetrahydro)-benzo-1, 3-dimethoxytetrahydrofuran is easily reduced in the presence of the homogeneous complex catalyst Rh-fluorescein. ::: ::: ::: ::: ::: 2. ::: ::: Cyclohexene derivatives, having a methyl group at the double bond, are not hydrogenated on homogeneous catalysts. ::: ::: ::: ::: ::: 3. ::: ::: The heterogeneous catalyst Rh/Al2O3, when compared with the homogeneous catalyst Rh-fluorescein, is less sensitive to the presence of a methyl group at the C=C bond in the cyclohexene ring. | Our recent nanoindentation measurements on phage lambda, revealed an evolutionary optimization of DNA density in viral capsid. Based on these experimental data, we proposed that water hydrating DNA in the capsid, provides significant support against external capsid deformation at wild-type DNA packing density. Shorter DNA length mutants are on the other hand two times weaker just like empty capsids. In this work, we perform a stringent test of this assumption. DNA hydration force can be dramatically decreased by addition of multivalent ions (here Mg2+ and Sp4+). Indeed, AFM measurements demonstrate that spring constant for wt-DNA phage lambda decreases to a value of an empty capsid upon addition of multivalent salt compared to the “zero-added-salt” value obtained in the previous work. This data is systematically analyzed with DNA hydration model and further comparison is made with phage fi29. | eng_Latn | 26,250 |
Reversible Hierarchical Assembly of Trimeric Coiled-Coil Peptides into Banded Nano- and Microstructures | We report a set of coiled-coil peptides, radially functionalized with bipyridines, that demonstrate hierarchical assembly into banded rectangular nano- and microstructures, the dimensions of which vary with the strategic placement and number of aromatic groups on the monomer backbone. Finer structural aspects of the hexagonal packing of the individual trimers were determined by X-ray scattering, including intertrimer aromatic interactions between bipyridine moieties. The ease of formation of these biomaterials under physiological conditions and the use of pH to reversibly modulate assembly demonstrate future potential for a range of biological applications, such as drug delivery in a pH-controlled manner. | Research on morphological control in block copolymers under the following four categories: thermoreversible morphology transitions, discovery of new morphologies, the control of morphology by blending and other control methods, is reviewed | eng_Latn | 26,251 |
Viscosity of Nanofluids. Why It Is Not Described by the Classical Theories | Transport properties of nanofluids are extensively studied last decade. This has been motivated by the use of nanosized systems in various applications. The viscosity of nanofluids is of great significance as the application of nanofluids is always associated with their flow. However, despite the fairly large amount of available experimental information, there is a lack of systematic data on this issue and experimental results are often contradictory. The purpose of this review is to identify the typical parameters determining the viscosity of nanofluids. The dependence of the nanofluid viscosity on the particles concentration, their size and temperature is analyzed. It is explained why the viscosity of nanofluid does not described by the classical theories. It was shown that size of nanoparticles is the key characteristics of nanofluids. In addition the nanofluid is more structural liquid than the base one. | Uncertainties in neutrino interaction cross-sections affect modern long-baseline neutrino oscillation experiments like NOvA. Detailed within is how NOvA handles these uncertainties, especially for 2p2h interactions, how the effects of these cross-section uncertainties are quantified, and how NOvA’s cross-section simulation is tuned to better match data. | eng_Latn | 26,252 |
ION EXCHANGE OF NA+ WITH RESIN CARBOXYLIC PROTONS | Abstract The degree of exchange of Na + with resin carboxylic protons as a function of pH was measured by titration. The ion-exchange behaviour was characterized with a model in which the assumptions were made that the resin has two types of carboxylic sites with different reactivities and the reactivity of each site decreases steadily as the extent of the exchange increases. The equilibrium conditions derived for the exchange reactions are expressed by a concentration ratio term and an exponential term for the coverage of the exchanged site, analogous to the Frumkin isotherm. The constants included in the model were determined by multiparametric curve fitting. Fitting with other models were also attempted. It was found that the proposed model provides the best description of the experimental data. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | yue_Hant | 26,253 |
Reinvestigation of the ponzio reaction for the preparation of gem-dinitro compounds | This paper presents some recent work to re-investigate the Ponzio reaction for the conversion of oximes to the gem-dinitro group. The Ponzio reaction is one of a number of less aggressive non-acidic methods used to nitrate aliphatic compounds, which are usually destroyed in the mixtures of nitric and sulphuric acids commonly used to nitrate aromatic compounds. The effect of varying the Ponzio reaction solvent, and of changing the nitrating species from N2O4 to N2O5 will also be presented. The reaction mechanism will be discussed with reference to N-15 CIDNP nmr studies. Where relevant the results will be compared with other aliphatic nitration methods. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,254 |
Affinity chromatography—Specific separation of proteins | This review covers the latest publications in the field of affinity chromatography and its merits and limits for the isolation and purification of proteins, with particular emphasis on enzymes. The literature considered in this survey includes mainly, in tabulated form, the papers published from 1969 to spring 1971. Various “affinants” and matrices are discussed and critically appraised with a view to the stabilisation of enzymes on matrices. | Abstract By using high-resolution time-of-flight neutron powder diffraction, we have investigated phase segregation in the narrow-bandwidth manganite Pr 0.7 Ca 0.3 MnO 3 . Unexpectedly, our data clearly demonstrate that phase segregation in Pr 0.7 Ca 0.3 MnO 3 is unrelated to electronic phase segregation, but is primarily driven by chemical disorder and intra-granular strains, similar to martensitic phase transitions. | eng_Latn | 26,255 |
Study on HPLC Fingerprint of Compound Danshen Tablets | OBJECTIVE: To establish HPLC fingerprint of Compound danshen tablets.METHODS: The separation was performed on Agilent Eclipse XDB-C18(150 mm×4.6 mm,5μm) column with mobile phase consisted of acetonitrile-0.04% phosphate (gradient elution) at flow rate of 1.0 mL·min-1.Detection wavelength was set at 272 nm and column temperature was 30℃.RESULTS: Established HPLC fingerprint was distinct and reproducible.There were 8 characteristic peaks among which No.5 characteristic peaks,No.6,No.7,No.8 came from HPLC fingerprint of Salvia miltiorrhiza and No.1 characteristic peaks,No.2,No.3,No.4 came from HPLC fingerprint of Panax notoginseng.CONCLUSION: The characteristic peaks of effective parts of Compound danshen tablet mainly come from S.miltiorrhiza.The study can be used for tracing and isolation of effective part of Compound danshen tablet and establishes basis for the further development of Chinese patent drugs. | Simulated annealing of chemical potential located the highest affinity positions of eight organic probes and water on eight static structures of hen egg white lysozyme (HEWL) in various conformational states. In all HELW conformations, a diverse set of organic probes clustered in the known binding site (hot spot). Fragment clusters at other locations were excluded by tightly-bound waters so that only the hot-spot cluster remained in each case. The location of the hot spot was correctly predicted irrespective of the protein conformation and without accounting for protein flexibility during the simulations. Any one of the static structures could have been used to locate the hot spot. A site on a protein where a diversity of organic probes is calculated to cluster, but where water specifically does not bind, identifies a potential small-molecule binding site or protein–protein interaction hot spot. | eng_Latn | 26,256 |
Variational approach to the conformation of flexible polymers in solution | Approximate solutions to the self‐consistent reference interaction‐site model (RISM) integral equation theory of polymer liquids are employed to study the conformational properties of flexible polymers as a function of density and chain length. The nonlinear nature of the expression describing the medium‐induced potential between two sites along the polymer chain necessitates the use of approximate methods to determine the intrachain pair‐correlation function consistent with the interchain packing. In the limiting case where the polymer segment hard‐core diameter approaches zero and the number of interaction sites comprising the chain goes to infinity, with the segment volume fraction held fixed, the intrachain pair correlation function is determined through a Feynman variational procedure for the effective free energy of a single chain in solution. The screening of the excluded volume interactions and the corresponding reduction of the polymer dimensions as a function of both polymer density and chain le... | The present invention relates to the use of a combination of preparatory steps in conjunction with mass spectrometry and time of flight detection methods to maximize the diversity of biopolymers can be verified in the particular sample. Then, the population of biopolymers verified in such a sample is be inspected for its ability Teru's evidence at least one condition, whereby the diagnostician, the relative presence and / or recognition of the absence of the biopolymer at least give the ability characterizes any single pathology presence or absence, and predicting the risk assessment of disease, and it is possible to expand the treatment for the disease. | eng_Latn | 26,257 |
Composite material with increased adhesion force, method of its production and application, in particular, in cigarette filters | FIELD: technological processes. SUBSTANCE: invention relates to a composite material with higher force of adhesion made of at least one polymer and at least one compound selected from silicon dioxide and activated coal, at the same time the specified composite material has the following: average particle size of at least 100 mcm, porous volume (Vd1), formed by pores with diameter from 3.6 to 1000 nm, of at least 0.2 cm 3 /g, force of adhesion such that content of particles in it with size of less than 100 mcm, produced under air pressure of 2 bar, makes less than 1.5 vol. %, is preferably equal to 0.0%. Also a method to produce a composite material is described, as well as its usage as a liquid medium carrier, a catalyst carrier, an additive or for filtration of liquid or gas, in particular, in cigarette filters. EFFECT: invention provides for high properties of hazardous components reduction in filtered medium. 33 cl, 2 tbl, 5 ex | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,258 |
The effect of the saturation and isomerization of dietary fatty acids on the osmotic fragility and water diffusional permeability of rat erythrocytes. | Weanling rats were fed semi-purified diets containing 15% by weight of either corn oil, a high oleic acid safflower oil, lard or hydrogenated soybean oil. Significant changes in the fatty acid composition of erythrocytes were induced by these dietary fats. The compositional changes did not effect water diffusional permeability, but did affect their osmotic fragility. An increased fragility appeared to be associated with an increased octadecenoate content of the membranes. | Dendrimers have tremendous potential application in the construction of novel nanocomposite materials. Thus, it is of great importance to understand the dendrimer–surface interaction. In this work, we have used fully atomistic molecular dynamics simulation to study the behavior of polyamidoamine (PAMAM) dendrimers adsorbed on the polarizable model of the gold surface. The structural properties of a single adsorbed PAMAM dendrimer as well after film formation were considered at three different solution pH’s. Based on calculated structural features such as radius of gyration, asphericity, distribution of terminal groups, and solvent-accessible surface area, we find that with an increase in pH dendrimers adopt a more compact, compressed structure. Moreover, the structure of individual dendrimers can undergo a further transition after aggregation compared to the isolated polymer. | eng_Latn | 26,259 |
Reversible Destabilization of UV‐Responsive Polymer Particles (Latex) using a Photoresponsive Surfactant | Production of aqueous dispersions of polymeric nanoparticles via heterogeneous radical polymerization in emulsion-type systems is of enormous commercial importance. The ability to reversibly destabilize such a latex is highly desirable, for example, to save transportation costs. Herein, a method for synthesis of photo-responsive polymer latexes that can be destabilized (leading to sedimentation) by only using UV irradiation (no addition of chemicals or change in the experimental conditions) and subsequently redispersed by stirring under visible light irradiation is described. The destabilization/redispersion mechanism relies on photoinduced trans-cis isomerization of the cationic diazene surfactant 2-(4-(4-butylphenyl)diazenylphenoxy)ethyltrimethylammonium bromide (C4AzoTAB) used in conjunction with the anionic surfactant sodium dodecyl sulfate. It is demonstrated that reversible destabilization can be achieved very rapidly (90 s residence time) employing continuous flow technology. | Abstract The overall aim of this chapter is to provide an introduction to thermodynamics of protein solutions applied to understanding how cosolvents, such as salts, osmolytes, or denaturants, impact upon protein stability and denaturation and protein phase behavior. This is especially relevant for any type of protein formulation or in bioseparation processes where a key variable is the cosolvent composition, which often needs to be manipulated to maintain protein stability and/or control protein solubility. The emphasis is on a molecular perspective, which is achieved by relating thermodynamic properties to protein–solvent and protein–protein interactions. Using a molecular approach provides a link through knowledge of intermolecular interactions between protein solution behavior and the protein physicochemical properties and solvent conditions, which, in turn, allows for some level of predictability. | eng_Latn | 26,260 |
Density fluctuations and structure of amorphous polymers | A comparison of density fluctuation, estimated from the different equations, has been done. It was shown that density fluctuation can be calculated from the values of the volume of a fluctuational free volume minimum hole. The concentration fluctuation can be calculated from the structural characteristics of amorphous polymers. This parameter serves as the characteristic of the degree of the nonuniformity of a structure in the amorphous state of polymers. | The development of aptamers on custom synthesized DNA microarrays, which has been demonstrated in recent publications, can facilitate detailed analyses of sequence and fitness relationships. Here we use the technique to observe the paths taken through sequence-fitness space by three different evolutionary regimes: asexual reproduction, recombination and model-based evolution. The different evolutionary runs are made on the same array chip in triplicate, each one starting from a small population initialized independently at random. When evolving to a common target protein, glucose-6-phosphate dehydrogenase (G6PD), these nine distinct evolutionary runs are observed to develop aptamers with high affinity and to converge on the same motif not present in any of the starting populations. Regime specific differences in the evolutions, such as speed of convergence, could also be observed. | eng_Latn | 26,261 |
Effects of heat treatment at two temperatures on the myosin cluster of bighead carp for gel formation | The α-helix of myosin decreased and the diameter of the myosin clusters increased monotonically with increasing heating time at 50 and 90°C. The clusters that formed during heating at 90°C were much larger than those that formed at 50°C. With increasing heating time, the G′ of the myosin heated at 50°C increased, but it decreased in the myosin heated at 90°C. The rheology data suggested that myosin heated at 50°C exhibited better gel formation than myosin that was heated at 90°C. The myosin gel network formed at 50°C was more consistent and homogeneous, whereas the gel formed 90°C was irregular and sturdy. Myosin heated at 50°C tended to form small, open clusters via heads, and the tails were outstretched, whereas the clusters that formed via myosin heads and tails at 90°C were larger and closed. | Protein immobilization in a specific conformation or orientation at an interface is influenced by specific interactions with the outer layer of the surface. A strategy to build-up a complex construct which is able to orient protein molecules, based on metal-cation chelation processes, is reported. The proposed methodology implies the formation of a mercaptoundecanoic acid monolayer on a gold surface that is activated to attach covalently the tripeptide glycyl-l-histidyl-l-lysine (GHK) on the surface, whose sites are then employed to chelate copper ions, providing a selective platform for the orientation of human serum albumin (HSA) molecules. The protein adsorption process on GHK and GHK–Cu(II)-complex surfaces was monitored by the in situ quartz crystal microbalance with dissipation monitoring (QCM-D) and force spectroscopy technique. The changes in frequency and dissipation factor as well as the D–f plots from QCM-D measurements help to characterize the changes in the protein conformation and are confir... | eng_Latn | 26,262 |
Improved performance of graphene doped with pyridinic N for Li-ion battery: a density functional theory model. | The performance of N-doped graphene on Li-ion battery has been investigated systematically by means of a density functional theory method. Pyridinic N doping, graphitic N atoms and 5-8-5 double vacancies have been selected as the functional defects to study their influence on Li storage compared to the pristine graphene. It has been confirmed that introducing pyridinic N atoms with p-type doping is a suitable method, especially for graphene doped with 4 pyridinic N atoms, whose structural distortion induced by Li intercalation is small and supplies strong force for Li adsorption. The diffusion barrier for this model is lower than for pristine graphene, both for the side and center diffusion routes, contributing to the high mobility. In addition, we point out that the strong catch force for Li will cause more Li to stay on the pyridinic N-doped graphene during the charge-discharge cycles, leading to a faster decrease of capacity compared to pristine graphene. | Staphylococcus aureus, a Gram positive coccal bacterium is a major cause of nosocomial infection. We report the synthesis of new triphenylamine phosphonium ionic liquids which are able to self-assemble into multiwall nanoassemblies and to reveal a strong bactericidal activity (MIC=0.5mg/L) for Gram positive bacteria (including resistant strains) comparable to that of standard antibiotics. Time kill, metabolism and fluorescence confocal microscopy studies show a quasi-instantaneously penetration of the nanoassemblies inside the bacteria resulting of a rapid blocking (30min) of their proliferation. As confirmed by rezasurin reduction monitoring, these compounds strongly affect the bacterial metabolism and a Gram positive versus Gram negative selectivity is clearly observed. These fluorescent phosphonium ionic liquid might constitute a useful tool for both translocation studies and to tackle infectious diseases related to the field of implantology. | eng_Latn | 26,263 |
Colloid Propulsion A Re-Evaluation, with an Integrated Design | A fully integrated micro-fabricated concept design of a colloid thruster is presented. A review of the possible mission applications for this thruster is provided, which concludes that the colloid thruster is versatile and shows good system advantages for missions as diverse as fundamental science missions, requiring high thrust stability, to low power consumption, high performance missions for small satellites. | We studied the dynamics of isolated vesicles as well as vesicle interactions in semi-dilute vesicle suspensions subjected to a shear flow. We found that the long-range hydrodynamic interactions between vesicles give rise to strong fluctuations of vesicle shape and inclination angle, , though the functional dependence of and the transition path to tumbling motion is preserved. The dependence of the suspension viscosity on the viscosity ratio between inner and outer fluids, ?, was found to be non-monotonic and surprisingly growing with ? at the fixed outer fluid viscosity for ?<1, at odds with recent predictions made for a dilute suspension of non-interacting vesicles. | eng_Latn | 26,264 |
Nonlinear positron acoustic solitary waves | The problem of nonlinear positron acoustic solitary waves involving the dynamics of mobile cold positrons is addressed. A theoretical work is presented to show their existence and possible realization in a simple four-component plasma model. The results should be useful for the understanding of the localized structures that may occur in space and laboratory plasmas as new sources of cold positrons are now well developed. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,265 |
Acid phosphatase from tobacco leaves. | Abstract An acid phosphatase capable of hydrolyzing phosphomonoester and phosphate anhydride bonds has been extracted from tobacco leaves and purified over 300-fold. The activity of the enzyme is optimal at pH 5.5–5.7 and does not require the presence of divalent cations. The enzyme possesses high activity toward ribonucleoside di-and triphosphates and 3′-monophosphates, much less activity toward ribonucleoside 2′- and 5′-monophosphates and glucose 1-phosphate, and no activity toward RNA or phosphodiesters. ATP, ADP, P-P i , and phosphoenolpyruvate competitively inhibit hydrolysis of p -nitrophenyl phosphate, suggesting that a single enzyme is responsible for all these activities. On the other hand, among the substances tested, activity toward β-glycerophosphate is considerably more sensitive to very small amounts of ammonium molybdate and to heat. Ammonium molybdate and P i competitively inhibit hydrolysis of p -nitrophenyl phosphate; NaF acts as a noncompetitive inhibitor. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,266 |
Hollow aggregations of moon jellyfish (Aureliaspp.) | The relative importance of behavior and currents in forming and maintaining jellyfish aggregations is not completely understood; the objective of this work was to determine how the physical properties of the water column were related to the formation of hollow aggregations of moon jellyfish (Aurelia spp.). Hollow aggregations were observed near the surface by airborne lidar in shallow water ( | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,267 |
Study of non-ionic surfactants in wool scouring | The features of non-ionic surfactants are introduced. By contrasts and analyses,it is shown that applying the non-ionic surfactants in wool scouring, can effectively improve the quality of the scoured wool, and the disposal waste water is easy.It is a group of satisfactory detergent. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,268 |
Reflection of Neutrons from a Polymer Layer Adsorbed at the Quartz-Water Interface | The segment density profile of a homopolymer adsorbed at a single solid-liquid interface has been determined using neutron specular reflection. The polymer was polyethylene oxide (PEO) of relative molecular mass 145 000 adsorbed from solution in water or MgSO4/water at the amorphous quartz/water interface. The fraction of polymer within the first 40 A of the surface was found to be between 0.7 and 0.8, and there was a negligible fraction beyond about 80 A. These dimensions compare with estimated values of 200 A for the radius of gyration and 21 A for the statistical segment length. The polymer is adsorbed into a narrower layer than predicted by simple theoretical models. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,269 |
Optimization of Phenolic Monomer Production from Solvent Liquefaction of Lignin | Process conditions used for solvent liquefaction of technical lignin in mixtures of o-cresol and tetralin were explored for optimizing the yield of phenolic monomers (PM) and liquid products. The effects of solvent mixture, reaction temperature, solids loading, and residence time were evaluated using a central composite response surface statistical model. Six response variables were monitored to evaluate the influence of the four factors. Liquid and solid yield were tracked via mass balance. The yield of distillable products (distillate) was determined using a thermogravimetric analyzer (TGA). Gas chromatography (GC) was used to monitor the individual yields of phenol, guaiacol, and 2,6-xylenol. Tetralin, which served as a hydrogen donor, was most effective in enhancing liquid production, reducing solid products, and increasing selectivity toward PM when present at less than 30 wt % of the solvent mixture. The interaction of solids loading and solvent mixture further indicated o-cresol was more effective ... | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,270 |
Influence of pregrafting cotton fabrics on kinetics of DMEU finishing | Cotton fabrics were pregrafted with a mixture of N-methylolacrylamide and methacrylic acid at mixing molar ratio of 4/6. The influence of pregrafting on the kinetics of finishing with 1,3-dimethylolethylene urea was studied. The results shows that pregrafting can increase the rate constants. Values of E a , ΔH*, ΔS*, and ΔG* suggest that the pregrafting of cotton fabric not only affects the reaction action state, but also is beneficial for the reaction between cellulose and the finishing agent. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,271 |
Lactoferrin and transferrin damage of the Gram-negative outer membrane is modulated by Ca2+ and Mg2+ | Summary: Lactoferrin and transferrin have antimicrobial activity against selected Gram-negative bacteria, but the mechanism of action has not been defined. We studied the ability of lactoferrin and transferrin to damage the Gram-negative outer membrane. Lipopolysaccharide release by the proteins could be blocked by concurrent addition of Ca2+ and Mg2+. Addition of Ca2+ also blocked the ability of lactoferrin to increase the susceptibility of Escherichia coli to rifampicin. Transferrin, but not lactoferrin, increased susceptibility of Gram-negative bacteria to deoxycholate, with reversal of sensitivity occurring with exposure to Ca2+ or Mg2+. In transmission electron microscopy studies polymyxin B caused finger-like membrane projections, but no morphological alterations were seen in cells exposed to EDTA, lactoferrin or transferrin. These data provide further evidence that lactoferrin and transferrin act as membrane-active agents with the effects modulated by Ca2+ and Mg2+. | We report Nuclear Magnetic Resonance (NMR) data for both the In(1) and In(2) sites in the heavy fermion material CeRhIn$_5$ under hydrostatic pressure. The Knight shift data reveal a suppression of the hyperfine coupling to the In(1) site as a function of pressure, and the electric field gradient, $\nu_{\alpha\alpha}$, at the In(2) site exhibits a change of slope, $d\nu_{\alpha\alpha}/dP$, at $P_{c1} = 1.75$ GPa. These changes to these coupling constants reflect alterations to the electronic structure at the quantum critical point. | eng_Latn | 26,272 |
Painting with bacteria: Smart templated self assembly using motile bacteria | External control of the swimming speed of `active particles' can be used to self assemble designer structures in situ on the micrometer to millimeter scale. We demonstrate such reconfigurable templated active self assembly in a fluid environment using light powered strains of Escherichia coli. The physics and biology controlling the sharpness and formation speed of patterns is investigated using a bespoke fast-responding strain. | Summary: A medium containing propamidine is described which has high selective activity for the species Bacillus anthracis. The spore form of the organism is essential as inoculum for the medium. | eng_Latn | 26,273 |
Fabrication and Wettability of Colloidal Layered Double Hydroxide-Containing PVA Electrospun Nanofibrous Mats | We report a facile protocol of preparing colloidal layered double hydroxide/polyvinyl alcohol (cLDH/PVA) electrospun nanofibrous mats via direct incorporation of low-content cLDH nanoplatelets with PVA without aid of any surfactant. The as-prepared cLDH/PVA nanofibrous mats exhibit a uniform, smooth surface and enhanced temperatures of the onset decomposition and inflection compared with those of the electrospun mats of pristine PVA and solid powdery LDH/PVA (pLDH/PVA) with the same LDH content. Subsequent surface chemical modification enables the resulting cLDH/PVA fibrous mats to exhibit superhydrophobicity and adhesion to water droplets, which are distinctly different from the hydrophilicity of the unmodified cLDH/PVA fibrous mats. Our results involving the cLDH/PVA electrospun nanofibrous mats may allow designing a variety of electrospun composite nanofibers with homogeneous morphology and multiple properties. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,274 |
Novel DiR and SPIO nanoparticles embedded PEG-PLGA nanobubbles as a multimodalimaging contrast agent | Fluorescence dye DiR and superparamagnetic iron oxide nanoparticles (SPIONs) embedded in PEG-PLGA nanobubbles (DiR-SPIO-NBs) were produced using double emulsion method on a membrane of Shirasu porous glass (SPG). The nanobubbles encapsulated with DiR and SPIONs had a liquid core (perfluoropentane) and a PEG-PLGA shell. DiR-SPIO-NBs showed biocompatibility based on MTT cytotoxicity and hemolysis studies. The PFP encapsulated in the nanobubbles experienced phase transition under ultrasonic irradation. Nanobubbles dispersed well in saline over 3 months�» and the relaxivity was 127.9 mM -1 s -1 , suggesting that it could be used as a contrast agent in MRI. The MR and fluorescence images in vivo demonstrated that the signal intensity in the spleen and liver was significantly enhanced with the treatment of nanobubbles. In addition, results of ultrasound images suggested that the nanobubbles had persistent contrast ability. In conclusion, nanobubbles could be utilized as an US/MRI/fluorescence contrast agent. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,275 |
[Administration of aggregated beta-amyloid peptide (25-35) causes change in long-term potentiation in the hippocampus]. | A month after intracerebroventricular injection of aggregated beta-amyloid fragment 25-35 (7.5 nmol/ventricle), a significant change in in vivo long-term potentiation in hippocampus was demonstrated. The time course of the long-term potentiation was compared with that in sham-operated animals, a powerful and stable increase in the evoked potential amplitude was observed. This phenomenon can be related with the oxidative stress that was revealed in this model in our previous studies, and, as a consequence, with deterioration of ion homeostasis. | Dendrimers have tremendous potential application in the construction of novel nanocomposite materials. Thus, it is of great importance to understand the dendrimer–surface interaction. In this work, we have used fully atomistic molecular dynamics simulation to study the behavior of polyamidoamine (PAMAM) dendrimers adsorbed on the polarizable model of the gold surface. The structural properties of a single adsorbed PAMAM dendrimer as well after film formation were considered at three different solution pH’s. Based on calculated structural features such as radius of gyration, asphericity, distribution of terminal groups, and solvent-accessible surface area, we find that with an increase in pH dendrimers adopt a more compact, compressed structure. Moreover, the structure of individual dendrimers can undergo a further transition after aggregation compared to the isolated polymer. | eng_Latn | 26,276 |
Thenar insertion of abductor pollicis longus accessory tendons and thumb carpometacarpal osteoarthritis. | Although the etiology of osteoarthritis of the thumb carpometacarpal (CMC) joint remains unclear, some theories have focused on variations in the local anatomy of the abductor pollicis longus tendon insertion. This cadaver study of 68 specimens analyzed the relationship between a thenar insertion of an accessory abductor pollicis longus tendon and the presence and severity of thumb CMC osteoarthritis. The joint cartilage surfaces were visually graded for degenerative changes. Thirty-five of 68 specimens (51%) had a thenar insertion, most frequently inserting on either the abductor pollicis brevis or opponens pollicis fascia or muscle belly. No significant association between a thenar insertion and thumb CMC arthritis was observed. Conversely, increasing age was noted to have a significant association with degenerative joint disease. Thus, these findings indicate that a thenar slip of the abductor pollicis longus tendon does not correlate with the presence or severity of CMC osteoarthritis. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,277 |
THE AQUEOUS SOLUTION BEHAVIOR OF LARGE UNIVALENT IONS. A NEW TYPE OF ION-PAIRING1a | For large, unhydrated, univalent ions, a tightening of the surrounding water structure is a dominant feature of their aqueous solution behavior. As represented by their activity and osmotic coefficients, this corresponds to a rise in the coefficients above the Debye-Huckel limiting law, and the increase is larger, the larger the ion, but if both the cation and anion are such large hydrophobic ions, the hydrogenbonded water structure forces them together to maximize the water-water interactions and to minimize the disturbance to itself. This water structure-enforced ion-pairing is every different from the more usual electrostatic, or Bjerrum, type of ion-pairing, occurring oniy in water, or other highly hydrogen-bonded solvents, and being greater, the larger the ions and the smaller their charges. Some chemical results of this type of ion-pairing are discussed. (auth) | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | yue_Hant | 26,278 |
Ocean acidification increases larval swimming speed and has limited effects on spawning and settlement of a robust fouling bryozoan, Bugula neritina | Abstract Few studies to date have investigated the effects of ocean acidification on non-reef forming marine invertebrates with non-feeding larvae. Here, we exposed adults of the bryozoan Bugula neritina and their larvae to lowered pH. We monitored spawning, larval swimming, settlement, and post-settlement individual sizes at two pHs (7.9 vs. 7.6) and settlement dynamics alone over a broader pH range (8.0 down to 6.5). Our results show that spawning was not affected by adult exposure (48 h at pH 7.6), larvae swam 32% faster and the newly-settled individuals grew significantly larger (5%) at pH 7.6 than in the control. Although larvae required more time to settle when pH was lowered, reduced pH was not lethal, even down to pH 6.5. Overall, this fouling species appeared to be robust to acidification, and yet, indirect effects such as prolonging the pelagic larval duration could increase predation risk, and might negatively impact population dynamics. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,279 |
Synthesis and Antitumor Activity of Novel Nitrogen Mustard-Linked Chalcones | A series of nitrogen mustard-linked chalcones were synthesized and evaluated for their antitumor activity in vitro against the K562 and HepG2 cell lines. The aldol condensation of [N,N-bis(chloroethyl)-3-amino]-acetophenone (2) with aromatic aldehydes afforded the nitrogen mustard-linked chalcones. Among the analogs tested, compounds 5e and 5k exhibited significant anti-proliferation activities against K562 cells with IC50 values of 2.55 and 0.61 µM, respectively, which revealed higher cell toxicity than the standard drugs cisplatin (IC50 > 200 µM) and adriamycin (IC50 = 14.88 µM). The methoxyl and N,N-dimethyl groups on the B-ring of the chalcone frame enhanced the inhibitory activities against both the K562 and HepG2 cell lines. The structure–activity relationship study indicated that the inhibitory activities significantly varied with the position(s) and species of the substituted group(s). | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,280 |
Reproductive Output of Female Anopheles gambiae (Diptera: Culicidae): Comparison of Molecular Forms | Abstract Knowledge of ecological differences between the molecular forms of Anopheles gambiae Giles (Diptera: Culicidae) might lead to understanding of their unique contribution to disease transmission, to better vector control, and to identification of the forces that have separated them. We compared female fecundity measured as egg batch size in relation to body size between the molecular forms in Mali and contrasted them with their sibling species, Anopheles arabiensis Patton. To determine whether eggs of different egg batches are of similar “quality,” we compared the total protein content of first-stage larvae (L1s), collected <2 h after hatching in deionized water. Egg batch size significantly varied between An. gambiae and An. arabiensis and between the molecular forms of An. gambiae (mean batch size was 186.3, 182.5, and 162.0 eggs in An. arabiensis and the M and the S molecular form of An. gambiae, respectively). After accommodating female body size, however, the difference in batch size was not s... | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,281 |
Kinetics of formation of heterocyclic polymer networks. 4. Storage time effect | The effect of the time of preliminary storage at room temperature on the kinetics of HMDI trimerization at the fixed HMDI/ER ratio (85/25), and different concentrations of the catalyst, TEA, and the evolution of glass transition parameters of the end products in function of the curing reaction regime, were studied by calorimetry. It was established that both the activation energy E α and the pre-exponential factor In A increased, the longer the storage time, and both tended to decrease with the conversion α 1 The time for the onset of gelation t gel decreased, the higher the catalyst concentration and/or the longer the preliminary storage time the former proved to be a major factor controlling t gel . The glass transition temperatures T g for post-cured samples of series HT internally diluted with stiff oxazolidone heterocycles were systematically higher than those for samples of series LT cured at 393 K whatever the catalyst concentration and/or the storage time. | A brief statement concerning the way in which biopolymers may have originated in the nonbiological world is made, including experimental evidence. This also includes a discussion of such matters as the way in which the code might have originated, that is, the relationship between polypeptides and polynucleotides as well as the secondary and tertiary structure resulting from the primary structure determination. The importance of the interaction of biopolymers with lipids for the formation of limiting membranes, leading to the formation of cells and other self-organizing cellular type organelles, is discussed. Thus, the second critical physical-chemical problem for cellular organization, namely, the biopolymer-lipid interaction, is now coming under scrutiny, both in terms of synthetic systems as well as natural ones. | eng_Latn | 26,282 |
A textile-based wearable supercapacitor using reduced graphene oxide/polypyrrole composite | Abstract Wearable electronics such as supercapacitors have been extensively explored and developed. Textile-based composites hold excellent promise as suitable hosts for electronic devices for the development of smart garments. In the present work, a textile-based electrode is developed through modification with reduced graphene oxide (rGO) nanosheets and polypyrrole (PPy) nanospherical particles onto polyethylene terephthalate (PET) fabric. The conductive composites are used to fabricate flexible, all-solid-state supercapacitors by using a gel electrolyte. The optimum device delivers an areal capacitance of 0.23 F cm−2 at a scanning rate of 1 mV s−1, a volumetric capacitance of 5.5 F cm−3 at a discharge current density 1.6 mA cm−3, an energy density of 11 μWh cm−2 and a power density of 0.03 mW cm−2 corresponding to 6.86 mg cm−2 of electroactive materials loading. It also retains about 76% of the initial capacitance after 6000 cyclic voltammetric cycles and possesses excellent stability under bending. | Staphylococcus aureus, a Gram positive coccal bacterium is a major cause of nosocomial infection. We report the synthesis of new triphenylamine phosphonium ionic liquids which are able to self-assemble into multiwall nanoassemblies and to reveal a strong bactericidal activity (MIC=0.5mg/L) for Gram positive bacteria (including resistant strains) comparable to that of standard antibiotics. Time kill, metabolism and fluorescence confocal microscopy studies show a quasi-instantaneously penetration of the nanoassemblies inside the bacteria resulting of a rapid blocking (30min) of their proliferation. As confirmed by rezasurin reduction monitoring, these compounds strongly affect the bacterial metabolism and a Gram positive versus Gram negative selectivity is clearly observed. These fluorescent phosphonium ionic liquid might constitute a useful tool for both translocation studies and to tackle infectious diseases related to the field of implantology. | eng_Latn | 26,283 |
Longitudinal relaxation of initially straight flexible and stiff polymers. | The relaxation mechanism of an initially straight flexible or stiff polymer chain of length N in a viscous solvent is studied through Brownian dynamics simulations covering a broad range of time scales. After the short-time free diffusion, the chain's longitudinal reduction R2(0)-R2 approximately Nt1/2 at early intermediate times is shown to constitute a universal behavior for any chain stiffness caused by a quasisteady T approximately Nt(-1/2) relaxation of tensions associated with the deforming action of the Brownian forces. Stiff chains with a persistence length E > or = N are shown to exhibit a late intermediate-time longitudinal reduction R2(0)-R2 approximately N2E(-3/4)t1/4 associated with a T approximately N2E(-3/4)t(-3/4) relaxation of tensions affected by the deforming Brownian and the restoring bending forces. | Abstract The spatial configuration of the polysaccharide chain of chitin is discussed. It is concluded that the only arrangement which is sterically satisfactory and fits X-ray diffraction data is that of a “bent” chain. | eng_Latn | 26,284 |
The onset of double diffusive convection in a binary viscoelastic fluid saturated anisotropic porous layer | The onset of double diffusive convection in a binary viscoelastic fluid saturated anisotropic porous layer is studied using a linear and a weak nonlinear stability analyses. The modified Darcy law for the viscoelastic fluid of the Oldroyd type is used to model the momentum equation. The onset criterion for stationary and oscillatory convection is derived analytically. There is a competition between the processes of thermal, solute diffusions, and viscoelasticity that causes the convection to set in through oscillatory rather than stationary. The effect of anisotropy parameters, Darcy–Prandtl number, relaxation, and retardation parameters on the stability of the system is investigated. The nonlinear theory based on the truncated representation of Fourier series method is used to find the transient heat and mass transfer. The effect of various parameters on heat and mass transfer is also brought out. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,285 |
Self-Assembled Architectures from Biohybrid Triblock Copolymers | The synthesis and self-assembly behavior of biohybrid ABC triblock copolymers consisting of a synthetic diblock, polystyrene-b-polyethylene glycol (PSm-b-PEG113), where m is varied, and a hemeprotein, myoglobin (Mb) or horse radish peroxidase (HRP), is described. The synthetic diblock copolymer is first functionalized with the heme cofactor and subsequently reconstituted with the apoprotein or the apoenzyme to yield the protein-containing ABC triblock copolymer. The obtained amphiphilic block copolymers self-assemble in aqueous solution into a large variety of aggregate structures. Depending on the protein and the polystyrene block length, micellar rods, vesicles, toroids, figure eight structures, octopus structures, and spheres with a lamellar surface are formed. | This is a reply to the comment by Xiao, et al. on our recently published paper J. Phys. Chem. C 2019, 123, 12, 7074-7080. In our paper, we did a high-throughput search of all the I-III-IV class of half-Heusler compounds that might exist in cubic phase for various energy applications. We agree that, as suggested by Xiao, et al., doing energy above the compex hull analysis is indeed an important descriptor in high-throughput calculations. However, the literature reports that some of the compounds claimed by Xiao, et al. to be highly unstable are indeed already experimentally synthesised. This raises concerns about the correctness of their presented analysis. | eng_Latn | 26,286 |
Temperature dependence of the lattice constant in doped and nonstoichiometric GaAs, GaAs1−xPx, and GaP | Results of measurements of the GaAs, GaAs1−xPx, and GaP lattice constants in the range 300 to 700 K are presented. The resulting values of the thermal expansion coefficient and their temperature changes are discussed. | Abstract The overall aim of this chapter is to provide an introduction to thermodynamics of protein solutions applied to understanding how cosolvents, such as salts, osmolytes, or denaturants, impact upon protein stability and denaturation and protein phase behavior. This is especially relevant for any type of protein formulation or in bioseparation processes where a key variable is the cosolvent composition, which often needs to be manipulated to maintain protein stability and/or control protein solubility. The emphasis is on a molecular perspective, which is achieved by relating thermodynamic properties to protein–solvent and protein–protein interactions. Using a molecular approach provides a link through knowledge of intermolecular interactions between protein solution behavior and the protein physicochemical properties and solvent conditions, which, in turn, allows for some level of predictability. | eng_Latn | 26,287 |
Immobilization of Thermolysin by Water-Soluble Reactive Polyurethane: Influence of Charges on the Matrix and Metal-Exchange at the Active-Site | Thermolysin [EC 3.4.24.4] was immobilized by use of a carbamoyl sulfonated urethane prepolymer. The pH dependence of apparent activity of the immobilized thermolysin was dependent on the species of the introduced diamine; compared with the one obtained with hexamethylenediamine, that prepared with l-lysine showed an optimum pH shifted to the basic side while an addition of triethylenetetramine shifted the pH profile to the acidic side. The activity after repeated use was improved by treatment with glutaraldehyde and also by an addition of cobalt(II) ion. The metal ion at the active site of the immobilized enzyme was effectively (though not completely) replaced by a treatment with ethylenediaminetetraacetic acid and the successive addition of metal ion. | We have used the modified Oseen hydrodynamic interaction tensor along with iterative numerical solution of the coupled hydrodynamic interaction equations to calculate the rotational diffusion coefficients of macromolecular complexes composed of nonidentical spherical subunits. For the one structure, a prolate ellipsoid of revolution, for which exact solutions are available, a subunit model with the same length and volume gives asymptotic agreement with the Perrin equations. Other structures considered include plane polygonal rings, lollipops, and dumbbells. | eng_Latn | 26,288 |
A Papaverine-Selective Electrode with Ion-To-Electron Transducer Based on the Conducting Polymer Poly(α-naphthylamine) | A new all-solid-state ion-selective electrode, which is reversible to papaverine, has been constructed using the conducting polymer poly(α-naphthylamine) as an ion-to-electron transducer. The ion-selective membrane represents an ion association complex of papaverine with a silicon tungstate counteranion in the form of an electroactive substance dispersed in a PVC matrix. The stability of the electrode potential of the proposed electrode was evaluated using a ionometric technique. | We attempt quantitative implementation of a previous suggestion that asymmetric charge neutralization of DNA phosphate groups may provide part of the driving force for nucleosome folding. Polyelectrolyte theory can be used to estimate the effective compressive force acting along the length of one side of the DNA surface when a fraction of the phosphate groups are neutralized by histones bound to that side. A standard engineering formula then relates the force to the bending amplitude caused by it. Calculated bending amplitudes are consistent with the curvature of nucleosomal DNA and the overall extent of charge neutralization by the histones. The relation of the model to various aspects of nucleosome folding, including the detailed path of core-particle DNA, is discussed. Several other DNA-protein complexes are listed as examples of possible asymmetric charge-induced bending. | eng_Latn | 26,289 |
Collapsing the proton motive force to identify synergistic combinations against Staphylococcus aureus. | Pathways of bacterial energy metabolism, such as the proton motive force (PMF), have largely remained unexplored as drug targets, owing to toxicity concerns. Here, we elaborate on a methodical and systematic approach for targeting the PMF using chemical combinations. We began with a high-throughput screen to identify molecules that selectively dissipate either component of the PMF, ΔΨ or ΔpH, in Staphylococcus aureus. We uncovered six perturbants of PMF, three that countered ΔΨ and three that selectively dissipated ΔpH. Combinations of dissipators of ΔΨ with dissipators of ΔpH were highly synergistic against methicillin-resistant S. aureus. Cytotoxicity analyses on mammalian cells revealed that the dose-sparing effect of the observed synergies could significantly reduce toxicity. The discovery and combination of modulators of ΔΨ and ΔpH may represent a promising strategy for combating microbial pathogens. | External control of the swimming speed of `active particles' can be used to self assemble designer structures in situ on the micrometer to millimeter scale. We demonstrate such reconfigurable templated active self assembly in a fluid environment using light powered strains of Escherichia coli. The physics and biology controlling the sharpness and formation speed of patterns is investigated using a bespoke fast-responding strain. | eng_Latn | 26,290 |
Preparation of honeycomb-patterned polyimide films by self-organization | Microporous polymer films are attractive materials with potential application in the fields of electronics, photonics, and biotechnology. Chemical and thermal stabilities of the microporous polymer films are required for their materials application. Besides preparation by conventional photolithography, we have reported that honeycomb-patterned porous polymer films are prepared by a method utilizing the condensation of small water droplets on solutions of amphiphilic copolymers. Here, we show preparation of honeycomb-patterned microporous films of a thermally and chemically stable material, polyimide. A water-template-assisted honeycomb structure was formed from a polyion complex of polyamic acids and dialkylammonium salt. The pore size of films was controlled by the casting volume of polymer solution. The patterned polyion complex film converted into polyimide by simple chemical treatment, keeping the porous structure. Self-supporting microporous polyimide films are fabricated. The honeycomb-structured fi... | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,291 |
In situ Diffusion Studies Using Spatially Resolved Infrared Microspectroscopy | Spatially resolved infrared microspectroscopy is used in conjunction with the contact method to conduct in situ diffusion experiments of photocured polymer-dispersed liquid crystals (LCs). The system analyzed consists of a low-molecular-weight liquid crystal (E7) diffusing into a photopolymerizable monomer (NOA65). The measured concentration profiles were generated by monitoring the hydroxyl band of the monomer as a function of time and spatial position. The diffusion coefficients were calculated from least-squares fitting of the data. The system followed Fick's second law of diffusion. The diffusion coefficient for this system is (1.97 ± 0.2)(10-8) cm2/s. The morphology of the system after polymerization exhibited three distinct regions: nematic LC molecularly mixed in the cross-linked network of the polymer, nematic LC droplet gradient in the polymer matrix, and polymer fibers scattered in the continuous nematic LC. | We propose a setup which allows us to couple the electron spin degree of freedom to the mechanical motions of a nanomechanical system not involving any of the ferromagnetic components. The proposed method employs the strain-induced spin-orbit interaction of electrons in narrow gap semiconductors. We have shown how this method can be used for detection and manipulation of the spin flow through a suspended rod in a nanomechanical device. | eng_Latn | 26,292 |
Antibacterial activities of fluorescent nano assembled triphenylamine phosphonium ionic liquids. | Staphylococcus aureus, a Gram positive coccal bacterium is a major cause of nosocomial infection. We report the synthesis of new triphenylamine phosphonium ionic liquids which are able to self-assemble into multiwall nanoassemblies and to reveal a strong bactericidal activity (MIC=0.5mg/L) for Gram positive bacteria (including resistant strains) comparable to that of standard antibiotics. Time kill, metabolism and fluorescence confocal microscopy studies show a quasi-instantaneously penetration of the nanoassemblies inside the bacteria resulting of a rapid blocking (30min) of their proliferation. As confirmed by rezasurin reduction monitoring, these compounds strongly affect the bacterial metabolism and a Gram positive versus Gram negative selectivity is clearly observed. These fluorescent phosphonium ionic liquid might constitute a useful tool for both translocation studies and to tackle infectious diseases related to the field of implantology. | An extensive understanding in the molecular motions that occur in Nafion® should lead to important development of improved proton exchange membrane for use in fuel cells (PEMFC). As water molecules are added in the system, changes within the Nafion® chain definitely take place. To visualize such a process, molecular dynamics is especially useful. Can information gained at this level of details be useful to propose new molecules, with ultimately better physical properties, such as higher proton conductivity? For this purpose, we first computed non-bond parameters stemming from the study of the trifluorosufonic acid. They are inserted in the pcff force field. We then applied the procedure developed in our lab to extract the glass transition temperature of Nafion® with different water uptakes. The plasticization effect is first confirmed, fostering a molecular analysis. The particular behavior of the sulfur-sulfur distance is revealed, guiding the design of new monomers. | eng_Latn | 26,293 |
Novel Platinum(II)‐Diaminobiotin Complexes. Their Synthesis and Characterisation | The diaminobiotin ligand 1 (cis-3, 4-diamino-2-tetrahydrothiophene valeric acid) was reacted with potassium chloroplatinate and with diaquodiammine platinum(II) cation 3 to yield new platinum complexes which were coordinated in a bidentate fashion through the diamine function of the ligand and have [PtN2Cl2] and [PtN4] geometries respectively. | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,294 |
An experimental study on the proper criterion to judge the thermal performance of the nanofluids | Abstract This work is dedicated to finding a suitable measure to judge thermal performance of nanofluids. The importance of this issue arises from misleading claim of excess heat transfer of nanofluids compared to the base fluid, neglecting the hydraulic effects such as increase in pressure drop. To clarify the issue, the experimental setup with capability to create constant Reynolds number and constant pumping power is constructed. Thermal behavior of nanofluids of silicon oxide/water and aluminum oxide/water and distilled water in developing region of laminar flow regime is investigated. In this regard, the convective heat transfer coefficient within the finned tube heat exchanger is evaluated. According to the results, the concentration of nanoparticle in the base fluid will have a significant impact on the amount of deflection of these two criteria, so that by increasing the nanoparticle's concentration the difference between these two measures becomes greater. | Abstract The overall aim of this chapter is to provide an introduction to thermodynamics of protein solutions applied to understanding how cosolvents, such as salts, osmolytes, or denaturants, impact upon protein stability and denaturation and protein phase behavior. This is especially relevant for any type of protein formulation or in bioseparation processes where a key variable is the cosolvent composition, which often needs to be manipulated to maintain protein stability and/or control protein solubility. The emphasis is on a molecular perspective, which is achieved by relating thermodynamic properties to protein–solvent and protein–protein interactions. Using a molecular approach provides a link through knowledge of intermolecular interactions between protein solution behavior and the protein physicochemical properties and solvent conditions, which, in turn, allows for some level of predictability. | eng_Latn | 26,295 |
Swelling Behavior of Single-Chain Polymer Nanoparticles: Theory and Simulation | Cross-linking a single polymer chain with itself leads to soft nanoparticles with well-defined properties. We study such single-chain nanoparticles (SCNP) obtained by cross-linking in good and in poor solvents using Monte Carlo simulations and theoretical models. We show that SCNP obtained by cross-linking in poor solvents preserve their shape during swelling in good solvents only if the precursor chain is very long. In this case the Flory–Rehner model describes the swelling of SCNP. Shorter chains and SCNPs cross-linked in good solvent generate noncompact structures. Here we obtain a good theoretical description of the simulated swelling properties using a mean-field model by taking into account the cross-linking topology using the connectivity matrix of the cross-linked chain. The crossover between the two regimes can consistently be described using a scaling argument. We further show that the distances between cross-links along the chain contour follows the distribution for Gaussian chains after cross-... | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,296 |
5-(2,4-Dihydroxyphenyl)tetrazole Sesquihydrate | The structure of the title compound [4-(5-tetrazolyl)-1,3-benzenediol sesquihydrate, C 7 H 6 N 4 O 2 .3/2H 2 O] which crystallizes with two tetrazolylbenzenediol molecules per asymmetric unit together with three water molecules, has been determined by single-crystal X-ray diffraction at room temperature. The two molecules are linked through a hydrogen-bonded network to water molecules, forming layers extending along the bc face of the unit cell. | The purpose of this research was to synthesize and characterize gelatin and tamarind gum (TG)/carboxymethyl tamarind (CMT) gum-based phase-separated hydrogels. The hydrogels were thoroughly characterized using bright-field microscope, FTIR spectroscope, differential scanning calorimeter, mechanical tester, and impedance analyzer. The mucoadhesivity, biocompatibility, and swelling property of the hydrogels were also evaluated. The antimicrobial efficiency of ciprofloxacin (model antimicrobial drug) loaded hydrogels was studied against E. coli. The in vitro drug release was carried out in both gastric and intestinal pHs. Microstructural analysis suggested the formation of phase-separated hydrogels. FTIR studies suggested that CMT gum altered the secondary structure of the gelatin molecules. Presence of the polysaccharides within the hydrogels resulted in the increase in the enthalpy and entropy for evaporation of the moisture from the hydrogels. The mechanical studies indicated viscoelastic nature of the hy... | eng_Latn | 26,297 |
Recent Advances in Anionic Synthesis of Functionalized Polymers | Abstract There has been growing interest and research on new synthetic methods for the preparation of well-defined polymers with in-chain and chain-end functional groups. These functional groups in polymers can participate in (a) reversible ionic association; (b) chain extension, branching or crosslinking reactions with polyfunctional reagents; (c) coupling and linking with reactive groups on other oligomer or polymer chains; and (d) initiation of polymerization of other monomers. It is noteworthy that the use of end-functionalized polybutadienes formed by reaction of poly(butadienyl)lithium with 4,4′-bis(diethylamino)-benzophenone has been reported to provide marked improvements in the wear and traction properties of tires. In order to exploit the unique potential of functionalized polymers, it is important to consider the scope and limitations of current functionalization methodology using anionic polymerization. Anionic polymerization approaches the goal of synthesizing polymers with predictable, well-... | Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilm... | eng_Latn | 26,298 |
The Structure of E. coli IgG-Binding Protein D Suggests a General Model for Bending and Binding in Trimeric Autotransporter Adhesins | The Escherichia coli Ig-binding (Eib) proteins are trimeric autotransporter adhesins (TAAs) and receptors for IgG Fc. We present the structure of a large fragment of the passenger domain of EibD, the first TAA structure to have both a YadA-like head domain and the entire coiled-coil stalk. The stalk begins as a right-handed superhelix, but switches handedness halfway down. An unexpected β-minidomain joins the two and inserts a ∼120° rotation such that there is no net twist between the beginning and end of the stalk. This may be important in folding and autotransport. The surprisingly large cavities we found in EibD and other TAAs may explain how TAAs bend to bind their ligands. We identified how IgA and IgG bind and modeled the EibD-IgG Fc complex. We further show that EibD promotes autoagglutination and biofilm formation and forms a fibrillar layer covering the cell surface making zipper-like contacts between cells. | Abstract Several novel applications of Deep Eutectic Solvents (DESs) have emerged recently. With a growing interest in the field, there is an urge to understand formation and functioning of these solvents at molecular level, which in turn would assist in further designing of DESs. We herein performed molecular dynamics simulations on three of the commonly used type III DES, viz, reline, ethaline, and glyceline, which are mixtures of urea, ethylene glycol, and glycerol with choline chloride at eutectic composition. Our results explain the role of inter-molecular and intra-molecular hydrogen bonding and energies on formation of these DESs. Furthermore, the ability of these DESs to be altered in a desired way through a simple addition of water makes it versatile solution for several other applications. Hence, simulations are also performed on the aqueous DES solutions, which reveal the effect of water on intermolecular network of interaction existing within these DESs. | eng_Latn | 26,299 |
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