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Kinetic study of CO hydrogenation reaction over Fe–Co–Mn ternary catalyst
|
Abstract A new kinetic approach is presented to study the mechanism of the catalytic reaction of the hydrogenation of carbon monoxide on Fe–Co–Mn catalyst prepared by wet impregnation method over MgO support. The experimental data obtained by a fixed bed reactor are used for calculating the apparent activity energy of the LHHW kinetic models developed for the consumption of carbon monoxide, and formation of methane, alkenes and alkanes. Then, using the calculated activation energies and the available UBI–QEP relationships for the ternary catalyst and obtaining the relationships between the apparent activity energy of the LHHW kinetic model and the activity energy of surface elementary reactions involved in the kinetic equation extraction and by developing an appropriate software coupled with a genetic optimization algorithm, the surface binding energy of carbon, oxygen and hydrogen on the ternary catalyst are calculated.
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A fluorometric enzyme assay was developed to evaluate the ability of a variety of compounds to bind to and/or inhibit pyroglutamyl aminopeptidase I. Among these compounds were a series of chloromethyl ketone analogues of thyrotropin releasing hormone (TRH) which had previously been shown to possess TRH-like activity in the central nervous system and have now been found to be good inhibitors of pyroglutamyl aminopeptidase. Thus, it is suggested that the observed TRH-like CNS activity could derive indirectly from inhibition of endogenous TRH degradation by pyroglutamyl aminopeptidase I.
|
eng_Latn
| 31,500 |
Kinetics and mechanism of the reaction of photoinduced 9-aryloxy-1,10-anthraquinones with alcohols
|
A stepwise mechanism for the reaction of 9-aryloxy-1,10-anthraquinones with alcohols has been established, starting with nucleophilic 1,4-addition of a molecule of alcohol. A quantitative reactivity study has been carried out. Introduction of acceptor substituents into the anthraquinone nucleus substantially increases the reaction rate, while donor substituents reduce it. A qualitative correlation between the rate constants and the electron density at the C and O atoms of the reaction site has been established.
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Abstract Exposure of the dorsal skin of hairless mice to the light of a germicidal lamp under standardized conditions produces reproducible, time-dependent increases of putrescine and spermidine concentrations, and a decrease of spermine levels, concomitant with the increase of the rate of DNa synthesis. Systemic or topical treatment of the animals with α-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, completely prevents the uv light-induced rapid formation of putrescine, and diminishes the enhancement of polyamine turnover rates. A significant effect of the drug on the rate of DNA synthesis could not be shown. The model is suitable for the study of interrelations between polyamine metabolism and cell proliferation and for the screening of compounds designed as inhibitors of polyamine biosynthesis.
|
eng_Latn
| 31,501 |
Antioxidant flavonol glycosides in mulberry (Morus alba L.) leaves isolated based on LDL antioxidant activity
|
Oxidation of low-density lipoprotein (LDL) has been implicated in atherogenesis. Antioxidants that prevent LDL from oxidation may reduce atherosclerosis. We investigated LDL antioxidant activity and extracted compounds of mulberry (Morus alba L.) leaves. The LDL antioxidant activity of 60% ethanol extracted of mulberry leaves, which inhibits human LDL oxidation induced by copper ion, was determined on the basis of oxidation lag time and calculated as epigallocatechin 3-gallate equivalents (58.3 μmol of EGCG equivalent/g of dry weight). Three flavonol glycosides [quercetin 3-(6-malonylglucoside), rutin (quercetin 3-rutinoside) and isoquercitrin (quercetin 3-glucoside)] were identified as the major LDL antioxidant compounds by LC-MS and NMR. The amounts of these flavonol glycosides in mulberry leaves and mulberry-leaf tea were determined by HPLC. Our results showed that quercetin 3-(6-malonylglucoside) and rutin were the predominant flavonol glycosides in the mulberry leaves.
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Five new complexes, [(NH3)5Co(dicarboxylate)Co(NH3)5]X4 (dicarboxylate=oxalate, succinate, pimelate, fumarate, and maleate; X=ClO4− or Cl−), were synthesized by the reactions of [Co(hydrogen dicarboxylate)(NH3)5](ClO4)2 with [Co(NH3)5(H2O)](ClO4)3 and characterized by chromatographic behavior and electronic and NMR techniques. When maleate was used as the dicarboxylate, the formation of [(NH3)5Co(fumarate)Co(NH3)5]4+ as well as [(NH3)5Co(maleate)Co(NH3)5]4+ was observed. The IR and Raman spectra of [(NH3)5Co(oxalate)Co(NH3)5]4+ indicate that the symmetry of the oxalate ion in the complex may be approximated by D2h.
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eng_Latn
| 31,502 |
1-(2,5-Dimethoxyphenyl)-3-ferrocenyl-2-(1H-1,2,4-triazol-1-yl)prop-2-en-1-one
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In the title compound, [Fe(C5H5)(C18H16N3O3)], the propene plane is tilted from its parent cyclopentadienyl ring by a small dihedral angle [17.9 (5)°], whereas the triazole and dimethoxyphenyl groups are nearly perpendicular to the propene plane [dihedral angles 75.9 (2) and 67.9 (2)°, respectively]. The cyclopentadienyl rings exhibit an almost eclipsed geometry.
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Abstract Exposure of the dorsal skin of hairless mice to the light of a germicidal lamp under standardized conditions produces reproducible, time-dependent increases of putrescine and spermidine concentrations, and a decrease of spermine levels, concomitant with the increase of the rate of DNa synthesis. Systemic or topical treatment of the animals with α-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, completely prevents the uv light-induced rapid formation of putrescine, and diminishes the enhancement of polyamine turnover rates. A significant effect of the drug on the rate of DNA synthesis could not be shown. The model is suitable for the study of interrelations between polyamine metabolism and cell proliferation and for the screening of compounds designed as inhibitors of polyamine biosynthesis.
|
fra_Latn
| 31,503 |
Outcomes and Practice Preferences After Endophthalmitis Following Anti-VEGF Intravitreal Injection
|
Purpose:This study examines treatment-based outcomes of endophthalmitis due to antivascular endothelial growth factor (anti-VEGF) intravitreal injection and its effect on subsequent management of n...
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In six of seven cases, direct anodic oxidation of the ethynyl group of an ethynylphenyl-derivatized free-base porphyrin gave modified glassy carbon electrodes in which the porphyrin was strongly surface-bound, most likely in a perpendicular geometry through covalent attachment of the ethynyl group to a surface carbon atom. The porphyrins each contained an ethynylphenyl group in one meso position and varied in the groups present in the other three meso positions. Electrografted 5,10,15,20-tetrakis(ethynylphenyl)porphyrin, H21, which has ethynyl moieties in all four meso positions, has well-defined surface voltammetry and grows to multilayer levels upon repeated cyclic voltammetry (CV) deposition scans. Multilayering was not observed to the same degree for monoethynylphenyl-substituted porphyrins and became progressively less for porphyrins having groups in the 15-meso position that were more protective against ethynyl radical attack. Clean molecular monolayer-level coverage was observed for 5-ethynylphenyl...
|
eng_Latn
| 31,504 |
Mechanistic Study of Thermal Decomposition of Hexamethyldisilane by Flash Pyrolysis Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry and Density Functional Theory
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Thermal decomposition of hexamethyldisilane (HMDS) was studied from room temperature to 1310 K using flash pyrolysis vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). Decomposition pathways of HMDS and initial reaction intermediates were also investigated using density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. Unimolecular decomposition reactions of HMDS involving Si-Si and Si-C bond cleavage, as well as decomposition producing Me4Si and Me2Si: via a three-centered elimination, were determined as the initiation reactions. Me3SiSi(Me)2∙, Me4Si, Me3Si∙ and :SiMe2 were major products of the initiation reactions. These initial products were apt to decompose by homolytic reactions. Me2Si=CH2, :SiMe2, and other silene/silylene intermediates preferred decomposing through molecular eliminations. Both homolytic and molecular elimination reactions are important in the pyrolysis of HMDS.
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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.
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eng_Latn
| 31,505 |
Catalysts for Dehydrogenation of ammonia boranes
|
Several effective homogeneous catalysts for the dehydrogenation of amine boranes have been developed. The best catalyst uses an iridium complex, and is capable of dehydrogenating H3NBH3 (AB) and CH3NH2BH3 (MeAB) at comparable rates. Thermodynamic measurements using this catalyst demonstrate that the dehydrogenation of AB and MeAB is substantially exothermic, which has important implications for regeneration.
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Cationic fluorophore homodimer probes 1 and 2 bearing 7-aminocoumarin and naphthalimide dyes, respectively, connected via diethylenetriamine (DETA) spacer, have been developed to demonstrate the validity of our modular probe design on the basis of the triamine-based spacer.
|
eng_Latn
| 31,506 |
Synchrotron Infrared Radiation for Electrochemical External Reflection Spectroscopy: A Case Study Using Ferrocyanide
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Synchrotron infrared radiation has been successfully coupled through an infrared (IR) microscope to a thin-cavity external reflectance cell to study the diffusion controlled redox of a ferrocyanide solution. Excellent signal-to-noise ratios were achieved even at aperture settings close to the diffraction limit. Comparisons of noise levels as a function of aperture size demonstrate that this can be attributed to the high brilliance of synchrotron radiation relative to a conventional thermal source. Time resolved spectroscopic studies of diffusion controlled redox behavior have been measured and compared to purely electrochemical responses of the thin-cavity cell. Marked differences between the two measurements have been explained by analyzing diffusion in both the axial (linear) and radial dimensions. Whereas both terms contribute to the measured current and charge, only species that originate in the volume element above the electrode and diffuse in the direction perpendicular to the electrode surface are ...
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Abstract Asymmetric total synthesis of small ring macrolide stagonolide-E has been described in this communication. The main highlight of our synthetic strategy is the application of ME-DKR (metal enzyme combo dynamic kinetic resolution) reaction, asymmetric reduction with Noyori’s BINAL-H reagent system, stereoselective cross metathesis, and RCM (ring closing metathesis) reaction at a late stage enables us to achieve the synthesis of the target molecule in an efficient way.
|
eng_Latn
| 31,507 |
A group of diphosphine-thiosemicarbazone complexes of palladium: Efficient precursors for catalytic CC and CN coupling reactions
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Abstract Reaction of 4-R-benzaldehyde thiosemicarbazone (denoted in general as HL-R; where H stands for the dissociable acidic proton and R (R = OCH 3 , CH 3 , H, Cl and NO 2 ) for the substituent) with [Pd(dppe)(EtOH) 2 ] 2+ , generated in situ via interaction of [Pd(dppe)Cl 2 ] (dppe = 1,2-bis(diphenylphosphino)ethane) with AgNO 3 in hot ethanol, in the presence of triethylamine affords a group of orange complexes of the type [Pd(dppe)(L-R)]NO 3 . Structures of [Pd(dppe)Cl 2 ] and [Pd(dppe)(L-OCH 3 )]NO 3 have been determined by X-ray crystallography. In the [Pd(dppe)(L-R)]NO 3 complexes, the thiosemicarbazone ligands are coordinated to the metal center as monoanionic bidentate N,S-donors forming five-membered chelate rings. The [Pd(dppe)(L-R)]NO 3 complexes show intense absorptions in the visible and ultraviolet regions, which have been analyzed by TDDFT calculations. All the [Pd(dppe)(L-R)]NO 3 complexes are found to efficiently catalyze Suzuki-type C C and Buchwald-type C N coupling reactions.
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Objective To investigate the roles of antioxidant, pyrrolidine dithiocarbamate (PDTC) in severe acute pancreatitis (SAP). Methods Seventy two Wistar rats were randomly divided into sham-operation(SO) group, SAP group, and SAP previously treated with PDTC group. SAP was induced in rats by injection of 5% sodium taurocholate into biliopancreatic duct. Plasma TNF-α and IL-6 were determined at 1, 3, 6 and 12 hour after operations. Results The plasma cytokine TNF-α and IL-6 in SAP group increased obviously compared with that in SO group ( P 0.05). The TNF-α reached its peak at 1 h while IL-6 did at 3 h postoperatively. The treatment with PDTC, markedly decreased the plasma TNF-α and IL-6 level compared with that in SAP group ( P 0.05), and also ameliorated the histologic injury of pancreas. Conclusions PDTC, an inhibitor of NF-κB activation, might alleviate the inflammatory response in SAP by suppressing cytokine gene expression.
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eng_Latn
| 31,508 |
Light Regulation of Aptamer Activity: An Anti-Thrombin Aptamer with Caged Thymidine Nucleobases
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"Caged" derivatives of a 15 nucleotide ssDNA anti-thrombin aptamer have been synthesized in which thymidine nucleotides are modified with photolabile protecting groups. One caged thymidine in a key location is enough to completely mask the aptamer's function in respect to their affinity for thrombin and their inhibition of the blood clotting cascade. With light (366 nm) the caging group can be removed, yielding the unmodified active aptamer.
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Three crystal forms of the repressor protein TetR class D in complex with the palindromic 17 bp operator sequence containing T overhangs on both sides were obtained by hanging-drop vapor-diffusion methods using PEG 4000 and PEG monomethylether 5000 as precipitants. Although the crystallization conditions were very similar, up to three different crystal forms were observed in the same drop. The space groups are monoclinic C2, P21 and hexagonal P6122. The asymmetric units of the latter two crystal forms contain one repressor-operator complex. The crystal structures of these forms were solved by molecular replacement using the Tet-repressor molecule of the complex with tetracycline as a search model.
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kor_Hang
| 31,509 |
Aminopyrido[2,3-c]-1,2,6-thiadiazine 2,2-dioxides as laser dyes
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Abstract Measurements of the spectral and temporal characteristics and energy efficiency of the neutral and acidic species of 4-amino-1,7-dimethylpyrido[2,3-c]-1,2,6-thiadiazine 2,2-dioxide (compound N1 ) and 4-amino-7,8-dimethylpyrido[2,3-c]-1,2,6-thiadiazine 2,2-dioxide (compound N2 ) in dimethylsulphoxide and acetonitrile have been performed. Continuous lasing of N1 from 0 to 1 M total proton concentration reveals simultaneous lasing of the neutral (N) and acidic (A) species of N1 .
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Abstract Photosensitivity based practical applications of chalcogenide glasses such as high resolution inorganic photoresists require thorough understanding of the relations between the glass structure and the etching kinetics. In this paper we report on the selective wet etching of thermally evaporated As2Se3 thin films carried out using amine based solutions. The relation between photo- and thermo-induced structural changes in thin As2Se3 films and the decrease of the etching rate, increase of the etching process' activation energy respectively, was determined.
|
eng_Latn
| 31,510 |
UV and IR Studies on Heterofullerene C76BN
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Twenty-two possible isomers for C76BN were studied by INDO methods. The two most stable geometries are 52,53-C76BN and 29,28-C76BN, in which boron and nitrogen atoms are connected with each other and located at the 6/6 bond near the longest axis of C78(C2v). Electronic spectra of C76BN were investigated with INDO/SCI method. UV absorptions of C76BN are red-shifted compared with those of C78(C2v). The structures and IR spectra for the four stable isomers of C76BN were calculated by AM1 method. It was indicated that the substitution of the BN unit weakens the conjugation of carbon atoms, leading to the decrease of IR frequencies.
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The present invention is 2,4,4,4-tetrafluoro-1-ene and cis-1,1,1,4,4,4-hexafluoro-but-2-ene and compositions containing, and, in particular, as a heat transfer fluid, to its use.
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kor_Hang
| 31,511 |
Regioselective ortho alkylation of nitro indole, carbazole, benzothiophene and benzofuran
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Abstract Substituted indoles, carbazoles, benzothiophenes and benzofurans are important motifs in the pharmaceutical industry. Herein we report a novel, regioselective method to introduce alkyl substituents into position ortho of nitro groups by the addition of a Grignard reagent followed by subsequent oxidation with DDQ.
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A fluorometric enzyme assay was developed to evaluate the ability of a variety of compounds to bind to and/or inhibit pyroglutamyl aminopeptidase I. Among these compounds were a series of chloromethyl ketone analogues of thyrotropin releasing hormone (TRH) which had previously been shown to possess TRH-like activity in the central nervous system and have now been found to be good inhibitors of pyroglutamyl aminopeptidase. Thus, it is suggested that the observed TRH-like CNS activity could derive indirectly from inhibition of endogenous TRH degradation by pyroglutamyl aminopeptidase I.
|
eng_Latn
| 31,512 |
Chemistry of Benzocyclopropenes.1H-and13C-NMR. Spectra of 2, 5-dideuterio-1-fluorobenzocyclopropenium ion
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Preparation of 1, 1-difluorobenzocyclopropene (4) and of its 2, 5- and 3, 4-dideuterio derivatives 4a and 4b is reported. Upon ionization in cold fluorosulfonic acid, 4 affords 1-fluorobenzocyclopropenium ion (6). 1H- and 13C-NMR. spectra of 4 and 6 are assigned on the basis of the data for the specifically deuteriumlabelled compounds 4a and 6a. Hydrolysis of 6a leads to 2, 5-dideuteriobenzoic acid (7a).
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The photochemical ring expansion of dispiro substituted cyclobutane-1,3-diones in methanol has been investigated. The formation of ring expansion product was strongly dependent on the spiro ring size of dispiro substituent. The ring expanded acetal was obtained in a low yield when the spiro ring of dispiro substituted cyclobutane-1,3-diones was a five- or seven-membered ring. This is the first example of photochemical ring expansion from cyclobutane-1,3-diones. A mechanism is postulated.
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eng_Latn
| 31,513 |
Water Gas Shift Reaction ‐ Homogeneous
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This article presents a brief overview of the soluble metal complexes that catalyze the water gas shift in homogeneous solution. Also discussed are the reaction mechanisms of the catalytic cycles that may be functioning in acidic solution and in basic solution as well as for the Reppe hydroformylation of alkenes. ::: ::: ::: Keywords: ::: ::: water gas shift; ::: hydrogen; ::: carbon monoxide; ::: ruthenium; ::: rhodium; ::: platinum; ::: iridium; ::: Reppe hydroformylation
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Abstract : Research extending earlier studies of chemical alleviation of the reentry plasma sheath is reported in the areas of plasma sheath chemical composition, the effect of hydrogen on additive effectiveness, and the effect of additives on high power pulse transmission through the plasma sheath. (Author)
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eng_Latn
| 31,514 |
Structural characterization of a four-electron donating, doubly-bridging isocyanide in (μ-p-CH3C6H4NC)Mn2(Ph2PCH2PPh2)2(CO)4
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Abstract X-Ray crystallographic analysis of (μ- p -CH 3 C 6 H 4 NC)Mn 2 (Ph 2 PCH 2 PPh 2 ) 2 (CO) 4 is reported. The molecule consists of two manganese atoms joined by a single bond and bridged by two trans diphosphine ligands and the isocyanide. There are two terminal CO groups per Mn. The isocyanide carbon donates a pair of electrons to one Mn (MnC = 1.81 A) while the CN unit donates a second pair of electrons to the other Mn (MnN = 2.12 A, MnC = 2.14 A). The isocyanide is strongly bent with a CNC(phenyl) angle of 137°. The bonding of the isocyanide ligand is discussed.
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Abstract The reactions of MC12L2(M = Pt,Pd, or Ni; L = tertiary phosphine), IrCl(CO)L2 (L = PPh3,PMePh2) with carbon monoxide, methanol, triethylamine and the isolation of methoxycarbonyl derivatives of palladium, platinum and iridium are described. The compounds Ir(CO2Me)(CO)2L2 (L = PPh3 or PMePh2) add iodo methane to give IrI(CO2Me)(Me)(CO)L2.
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eng_Latn
| 31,515 |
Facile Synthesis of Metalloporphyrins-Ba2+ Composites as Recyclable and Efficient Catalysts for Olefins Epoxidation Reactions
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A facile co-precipitation method was developed to prepare the novel metalloporphyrins-Ba2+ composites with ca. 3 μm diameter and olive-like morphology. Olefins epoxidation reactions were employed to investigate their catalytic performance. Compared with the free metalloporphyrins, the composites exhibited not only the improved stability and recyclability, but also the enhanced catalytic activity. Such catalytic behaviors could be related to the unique structure of the composites, e.g., the strong interaction between R-SO3- and Ba2+ ions and the uniform distribution of metalloporphyrins on the catalyst surface, respectively. Furthermore, the composites showed good compatibility with a wide range of substrates. The well-designed composites are expected to be efficient catalysts, alternative to many sophisticated-synthesized metalloporphrins-based materials, in the industrially important reactions.
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We present an overview of advanced oxidation processes (AOPs) for removing different pesticides, with emphasis on the toxicity of degradation products and the bioanalytical techniques used to assess the toxicity. Inhibition of bioluminescence from Vibrio fischeri appears to be the most versatile indicator of toxic compounds generated in degradation processes for pesticides. However, detection of neurotoxic compounds, which can be generated in AOPs of some organophosphorous pesticides, requires acetylcholinesterase (AChE) bioassays that rely on inhibiting AChE activity. The novel AChE-flow-injection analysis (FIA)-thermal lens spectrometric (TLS) bioassay was recently applied with success for toxicity testing in degradation of organophosphates by AOPs.
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eng_Latn
| 31,516 |
Halo-Substituted Chalcones and Azachalcones Inhibited Lipopolysaccharited-Stimulated Pro-Inflammatory Responses through the TLR4-Mediated Pathway
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A series of B-ring, halo-substituted chalcones and azachalcones were synthesized to evaluate and compare their anti-inflammatory activity. Mouse BALB/c macrophage RAW 264.7 were pre-treated with 10 μg/mL of each compound for one hour before induction of inflammation by lipopolysaccharide (1 μg/mL) for 6 h. Some halo-chalcones and -azachalcones suppressed expression of pro-inflammatory factors toll-like receptor 4 (TLR4), IκB-α, transcription factor p65, interleukine 1β (IL-1β), IL-6, tumor necrosis factor α (TNF-α), and cyclooxygenase 2 (COX-2). The present results showed that the synthetic halo-azachalcones exhibited more significant inhibition than halo-chalcones. Therefore, the nitrogen atom in this series of azachalcones must play a more crucial role than the corresponding C-2 hydroxyl group of chalcones in biological activity. Our findings will lay the background for the future development of anti-inflammatory nutraceuticals.
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This paper reports on the development of optically based techniques to detect and identify chemical agents. Detection ::: sensitivity and molecule discrimination are studied. In parallel, efforts are made to develop rugged and compact ::: experimental designs that can be used for field measurements. Laser Induced breakdown spectroscopy (LIBS) is a ::: surface analyzing optical technique investigated to measure sarin like molecules deposited on samples coming from the ::: Parisian subway. On the other hand, Tunable Diode Laser Spectroscopy (TDLS) - Cavity Ring-Down Spectroscopy ::: (CRDS) or Cavity Enhanced Absorption Spectroscopy (CEAS) - is used to measure traces of the industrial toxic ::: hydrogen fluoride gas down to the ppb level. Measurements in laboratory are reported and primary results obtained in a ::: field experiment are described.
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eng_Latn
| 31,517 |
A process for preparing aryloxy or arylthio-2-2 optically active alkanoic acids
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A process for preparing 2-aryloxy or arylthio-2 acids optically active alkanoques by enantioselective hydrolysis of the corresponding racemic amides in the presence of a microorganism or an enzyme selected according to its ability to selectively hydrolyze alpha phenylpropionamide racemic alpha-phenylpropionic acid S.
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Japanese lacquer is a sole, enzymatically drying natural lacquer, giving films with excellent durability. Oligomerization of urushiol (1) (a major component of the lacquer) in the lacquer system was reviewed. The enzymic formation of the urushiol-quinone (3) from urushiol was studied by laccase-catalyzed reactions with pyrocatechols. On the basis of the separated urushiol dimers in both the lacquer and model reaction systems, a nonenzymatic CC and CO coupling reaction of the urushiol-quinone with the unsaturated chain or with the nucleus of urushiol is discussed as significant reaction path in the polymerization of Japanes lacquer. The films of the lacquer made by a mild oxidation process, a technique applied for so long time in practice, retained their dynamechanical properties completely over 16 years.
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eng_Latn
| 31,518 |
New heteroleptic iridium(III) nitro complexes derived from fac-[Ir(NO2)3(H2O)3]
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Abstract An aqueous solution of fac-[Ir(H2O)3(NO2)3] (1) was utilized as a starting material for preparation of the new heteroleptic iridium complex [Ir(H2O) (bpy) (NO2)3] (2). From alkaline solutions of 2, the salt Na [Ir(OH) (NO2)3 (bpy)]·2H2O was isolated and its structure was determined by X-ray structure analysis. Structures of new compounds 2 and 3 as well as the parent complex 1 was characterized using multinuclear magnetic resonance spectroscopy and mass spectrometry. The structures of parent fac-[Ir(H2O)3(NO2)3] and complexes 2 and 3 were probed by employing density functional theory (DFT) calculations.
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Purpose Given the fact that neuroimaging studies are currently not used routinely in the evaluation of concussions in the clinical setting, the diagnosis and management of concussion has centered around subjective symptom reports, clinical and neurocognitive examinations. Functional near-infrared spectroscopy (fNIRS), a noninvasive and portable neuroimaging modality that detects changes in blood oxygenation related to human brain function, is a promising tool to address this gap in the clinical evaluation of concussion. While fNIRS has recently demonstrated that adults with a concussion show reduced brain activation on neurocognitive tests compared to …
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eng_Latn
| 31,519 |
An Air‐Stable, Neutral Phenothiazinyl Radical with Substantial Radical Stabilization Energy
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The vital effect of radical states on the pharmacological activity of phenothiazine-based drugs has long been speculated. Whereas cationic radicals of N-substituted phenothiazines show high stability, the respective neutral radicals of N-unsubstituted phenothiazines have never been isolated. Herein, we describe SQH2• as the first air-stable neutral phenothiazinyl free radical. The crystalline dark-blue species is characterized by EPR and UV-Vis/NIR spectroscopy as well as cyclic voltammetry, spectro-electrochemical analysis, SCXRD and computation. SQH2• stands out from other aminyl radicals by an impressive radical stabilization energy - and its parent amine by one of the weakest N-H bond dissociation energies ever determined. Besides serving as open-shell reference in medicinal chemistry, its tridentate binding pocket or hydrogen-bond donor ability might enable manifold uses as redox-active ligand or proton coupled electron transfer reagent.
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SummaryThe metabolism of betahistine, demethylbetahistine and 2-(2-hydroxy-ethyl) pyridine in the rabbit leads to the urinary excretion of acidic metabolities, including 2-pyridylacetate, which is excreted in part as N-2-pyridylacetylglycine. Other unidentified Koenig-positive compounds were in the acidic fraction.
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eng_Latn
| 31,520 |
In pursuit of α4β2 nicotinic receptor partial agonists for smoking cessation: Carbon analogs of (−)-cytisine
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Abstract The preparation and biological activity of analogs of (−)-cytisine, an α4β2 nicotinic receptor partial agonist, are discussed. All-carbon-containing phenyl ring replacements of the pyridone ring system, generated via Heck cyclization protocols, exhibited weaker affinity and lower efficacy partial agonist profiles relative to (−)-cytisine. In vivo, selected compounds exhibit lower efficacy partial agonist profiles than that of (−)-cytisine.
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A generalized model of diffusion mass transfer of implanted dopant atoms (donors and acceptors) in crystalline silicon has been developed. It takes into account all possible charge states of diffusing species (vacancies, interstitial Si atoms, and “dopant atom-vacancy” and “dopant atom-interstitial silicon atom” pairs) and the difference between the diffusion coefficients of differently charged pairs. Expressions for the source/sink terms are derived which describe all bimolecular reactions between the species (generation and annihilation) in the course of diffusion with account for their charges.
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eng_Latn
| 31,521 |
Synthesis, characterization and molecular docking studies of N-(4-Bromo-2- fluorophenyl) malonamide
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The novel N-(4-bromo-2-fluorophenyl) malonamide has been efficiently synthesized from diethyl malonate (DEM) and NH3. Computational studies were undertaken to test the inhibitory effect of the synthesized molecule on protein kinase PKnB from Mycobacterium tuberculosis. Based on the virtual screening and molecular docking we found that N-(4-bromo-2-fluoro phenyl)malonamide showed good binding affinities with the active site pocket (comprising of VAL-95) of the PknB.
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The bond-stretching phonon modes of linear polyynes with hydrogen atom termination at the both ends are calculated as a function of chain length within the density functional theory. The frequency of one of two particular Raman active phonon modes monotonically decreases with the increase of polyyne chain length while that of the other one shows an oscillating behavior, consistent with previous Raman measurements. The relative Raman intensity of the two phonon modes are evaluated by optimized geometries for ground states and excited states. We also present a nuclear magnetic resonance (NMR) calculation for spin-spin coupling constants as a function of distance between hydrogen and carbon-13 nuclei and, within carbon-13 nuclei, up to the polyyne center of symmetry. We compare the calculated results with recent NMR experiments. (C) 2011 Elsevier Ltd. All rights reserved.
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eng_Latn
| 31,522 |
Bioelectrochemical Reaction Kinetics, Mechanisms, and Pathways of Chlorophenol Degradation in MFC Using Different Microbial Consortia
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Microbial fuel cell (MFC) is a sustainable technology for removing toxic pollutants such as chlorophenols, while generating electricity. Yet, there is lack of detailed study on understanding bioelectrochemical interactions within the complex biological, chemical, and electronic species in MFC system. This paper reports a new research approach to discover bioelectrochemical reaction kinetics, biodegradation pathways, and electrochemical reaction mechanisms of degradation of 2,4-dichlorophenol (2,4-DCP) in MFC, which was inoculated with industrial and domestic microbial consortia, referred to as iMFC and dMFC systems, respectively. The chlorophenol degradation was found to contribute electronic transfer and generation in MFC. Microbial growth and degradation kinetic results analyzed by Michaelis–Menten and Hanes–Woolf models showed that MFC is highly capable of degrading 2,4-DCP at high concentration (>30 mg/L). The biodegradation pathways and metabolites varied significantly in iMFC and dMFC under aerobic/...
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Purely organic room temperature phosphorescence (RTP) and ultralong RTP (OURTP) materials have attracted much attention recently, but it is challenging to integrate circularly polarized luminescence (CPL) to RTP/OURTP. Here, we show a strategy to realize CPL-active OURTP (CP-OURTP) by bonding achiral phosphor directly to the chiral center of an ester chain and this flexible chiral chain engineering enables efficient chirality transfer to carbazole aggregates, resulting in strong CP-OURTP with lifetime over 0.6 s and dissymmetry factor of 2.3×10 -3 after the conformation regulation upon photo-activation. Thus realized CP-OURTP is quite stable at room temperature but can be deactivated quickly at 50 o C to CP-RTP with high CPL stability during the photo-activation/thermal-deactivation cycles. Based on this extraordinary photo/thermal-responsive and highly reversible CP-OURTP/RTP, a CPL-featured lifetime-encrypted combinational logic device has been successfully established.
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eng_Latn
| 31,523 |
[Synthesis and bacteriostatic activity of thiosemicarbazone and their transition metal complexes].
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In this paper, 8 thiosemicarbazones and 12 transition metal complexes thereof have been synthesized and tested for bacteriostatic activity against five kinds of bacteria. The results show that hetero atom or substitution group in the o-position of the aryl ring to the carbonyl group in the aldehyde or ketone is essential to the bacteriostatic activity of the thiosemicarbazones, and different mechanisms of inhibition are followed by thiosemicarbazones and their complexes. The complexes displayed activity superior to the thiosemicarbazones.
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Documentary indications of the British patent specification 14 79 444 are traced through various machine-readable stores (OTAF, DERWENT, CASEARCH, CLAIMS/US) and various printed collections (claims of German Offenlegungsschriften, US and GB abstracts and Chemical Abstracts). The traceability of patents such as GB 14 79 444 (electrolytic cell with diaphragm and titanium anodes with a catalytically active coating of platinum or ruthenium and their compounds) using the IPC and free text terms is compared. Symptomatically, it was found that free text searches go further than IPC searches, because they can reach a greater search depth.
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eng_Latn
| 31,524 |
Aromatics to Diquinanes: AnExpeditious Synthesis of Tetramethyl-bicyclo[3.3.0]octaneFramework of Ptychanolide
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An expeditious route to methyl-7-oxo-1,4,5,8-tetra- methylbicyclo(3.3.0)octane-3-carboxylate from a simple aromatic precursor is described. Oxidative dearomatization of 2-hydroxy- methyl-3,4,6-trimethylphenol into spiroepoxycyclohexa-2,4-di- enone, its cycloaddition and triplet-sensitized 1,2-acyl shift, and stereochemical inversion are the key features of our methodology.
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AbstractAcetoin and 2,3-butanediol (2,3-BD) have a large number of industrial applications. The production of acetoin and 2,3-BD has traditionally relied on oil supplies. Microbial production of acetoin and 2,3-BD will alleviate the dependence on oil. Acetoin and 2,3-BD are neighboring metabolites in the 2,3-BD metabolic pathway of bacteria. This review summarizes metabolic engineering strategies for improvement of microbial acetoin and 2,3-BD production. We also propose enhancements to current acetoin and 2,3-BD production strategies, by offering a metabolic engineering approach that is guided by systems biology and synthetic biology.
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eng_Latn
| 31,525 |
Dynamics of carbocation formation in the photolysis of 1,2,2,3-tetramethyl-1,2-dihydroquinoline in alcohols
|
Dynamics of the formation of the carbocation in the ground state as a result of photoinduced proton transfer from a solvent to the excited state of 1,2,2,3-tetramethyl-1,2-dihydroquinoline (3MDHQ) in MeOH and 2,2,2-trifluoroethanol (TFE) was registered by pump-probe laser photolysis (λpump = 310 nm) with femtosecond time resolution. The lifetimes of the excited singlet state of 3MDHQ τ = 115 and 780 ps were determined in TFE and MeOH, respectively. The transient species with absorption spectrum corre-sponding to the spectrum of the carbocation from 3MDHQ (λmax = 480 nm) is generated at time delays lower than 500 fs from the unrelaxed excited singlet state.
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Abstract Exposure of the dorsal skin of hairless mice to the light of a germicidal lamp under standardized conditions produces reproducible, time-dependent increases of putrescine and spermidine concentrations, and a decrease of spermine levels, concomitant with the increase of the rate of DNa synthesis. Systemic or topical treatment of the animals with α-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, completely prevents the uv light-induced rapid formation of putrescine, and diminishes the enhancement of polyamine turnover rates. A significant effect of the drug on the rate of DNA synthesis could not be shown. The model is suitable for the study of interrelations between polyamine metabolism and cell proliferation and for the screening of compounds designed as inhibitors of polyamine biosynthesis.
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eng_Latn
| 31,526 |
Solving the Burgers-Huxley Equation by <i>G'/G</i> Expansion Method
|
By introducing and extending the G'/G expansion method with the aid of computer algebraic system “Mathematics”, the exact general solutions were obtained for the Burgers-Huxley equation and special form. Final results were represented in hyperbolic function, trigonometric function and rational function with arbitrary parameters.
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We have carried out molecular dynamics (MD) simulations and free energy calculations on the α-subtype of the human estrogen receptor ligand-binding domain (ERα LBD) complexed with a number of known agonists and putative xenoestrogens. Our dynamical simulations of ligand−receptor complexes underscore the highly structured nature of the complex and offer some interesting insights into the structure−activity relationship (SAR) for these ligands. With traditional thermodynamic integration (TI) calculations, we calculate relative binding free energies for three known agonists, in good agreement with experimental values. The sheer number of possible xenoestrogenic compounds makes an approach using traditional free energy calculations unfeasible. Instead, we have made use of a single-step perturbation methodology that allows the calculation of relative free energies for a large number of related polyaromatic hydrocarbons (PAHs) from a single simulation. Our results show good (maximum deviation 3.3 kJ mol-1) agre...
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eng_Latn
| 31,527 |
Et2SnCl2 · H2O and the Trigonal–Bipyramidal Transition State of a SN2 Reaction
|
Abstract The title compound Et2SnCl2 · H2O was prepared and characterized by IR-spectroscopy and single crystal X-ray diffraction, showing the typical trigonal bipyramidal structure of a SN2 transition state with the water molecule in an axial position. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT
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Abstract an easy two-step preparation of 1,1,6-trimethyl 1,2-dihydronaphtalene from α-ionone via 1,1,6-trimethyl 1,2,3,4-tetrahydronaphtalene is described.
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eng_Latn
| 31,528 |
The gaseous oxidation of acetone - I. The high-temperature reaction
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The gaseous oxidation of acetone has been studied at temperatures between 250 and 510°C at pressures up to 450 mmHg. In contrast to earlier reports, two oxidation régimes have been discovered, separated by a region where the rate of reaction decreases as the temperature rises. This paper presents the results of a detailed study of the kinetics and products of the reaction in the high-temperature region. The reaction is autocatalytic, and a reaction scheme is proposed which accounts for the principal experimental facts. This scheme involves degenerate chain branching, in which the oxidation of formaldehyde plays an important part.
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Abstract Photosensitivity based practical applications of chalcogenide glasses such as high resolution inorganic photoresists require thorough understanding of the relations between the glass structure and the etching kinetics. In this paper we report on the selective wet etching of thermally evaporated As2Se3 thin films carried out using amine based solutions. The relation between photo- and thermo-induced structural changes in thin As2Se3 films and the decrease of the etching rate, increase of the etching process' activation energy respectively, was determined.
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eng_Latn
| 31,529 |
Phytochemical screening and antimicrobial activity of stem bark extracts of Antidesma Venosum
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Chemical studies on stem bark of Antidesma venosum used in phytotherapy were done in vitro. The stem b ark was extracted by Soxhlet in absolute methanol, and part itioned using ethyl acetate, n-pentanol and distill ed water to give fractions coded EAA, NPE and AQE, respectively. Phy tochemical screening of crude methanol extract (CME ) and EAA showed presence of alkaloids, saponins, tannins and flavonoids; Saponins and tannins in NPE and AQ E. These fractions together with CME were screened for antim icrobial activity against Staphylococcus aureus, Sa lmonella typhi and Escherichia coli. The highest antimicrobi al activity was observed with EAA and least with AQ E. All fractions and extract however, exhibited some activ ity on tested microorganisms.
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A brief overview is presented of the VAMAS Surface Chemical Analysis Technical Working Party project. This project is aimed at providing the reference working base for surface analysis. There are currently 20 projects covering AES, XPS, SIMS, sputtered neutral mass spectrometry and sputter-depth profiling. The coordination of the projects leads to considerable gains in confidence and in project output, together with a reduction in the workload necessary to meet the project targets. This arises simply because of the increased availability of characterized samples, reference methodologies and software within the overall programme. This Technical Working Party has been active for 4 years now and definitive milestones are being achieved that would be impossible without the overall coordination.
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eng_Latn
| 31,530 |
Generation of trifluoromethyl thiolsulphonate through one-pot reaction of sulfonyl chloride and trifluoromethanesulfanylamides
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Abstract A novel and efficient tandem reaction of sulfonyl chloride and trifluoromethylsulfanylamide is described here for the synthesis of various trifluoromethyl thiolsulphonates with a broad functional group tolerance. In the process, it is believed that sulfinate generated from sulfonyl chloride is a critical intermediate and the additive 4-methylbenzenesulfonic acid ( p -TsOH) facilitates the formation of “CF 3 S + ”. Electrophilic trifluoromethylthiolation of in situ generated sulfinate and “CF 3 S + ” provides the final products.
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Conventional time-dependent density functional theory (TDDFT) is based on a closed-shell Kohn–Sham (KS) singlet ground state with the adiabatic approximation, using either linear response (KS-LR) or the Tamm–Dancoff approximation (KS-TDA); these methods can only directly predict singly excited states. This deficiency can be overcome by using a triplet state as the reference in the KS-TDA approximation and “exciting” the singlet by a spin flip (SF) from the triplet; this is the method suggested by Krylov and co-workers, and we abbreviate this procedure as SF-KS-TDA. SF-KS-TDA can be applied either with the original collinear kernel of Krylov and co-workers or with a noncollinear kernel, as suggested by Wang and Ziegler. The SF-KS-TDA method does bring some new practical difficulties into play, but it can at least formally model doubly excited states and states with double-excitation character, so it might be more useful than conventional TDDFT (both KS-LR and KS-TDA) for photochemistry if these additional ...
|
eng_Latn
| 31,531 |
Amiodarone N-deethylation in human liver microsomes : involvement of cytochrome P450 3A enzymes (first report)
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Abstract Experiments were conducted on three different human liver samples to identify the cytochrome P450 isozyme which is involved in the biotransformation of the class III antiarrhythmic agent, amiodarone, into its major metabolite, desethylamiodarone (DEA). The classic P450 inhibitors, SKF 525A, metyrapone, and carbon monoxide provided a significant reduction in the in vitro formation of DEA by human hepatic microsomes. Amiodarone N -deethylase activities expressed by intrinsic clearance values were similar in all the livers used, although two livers were genotyped as extensive and one as a poor metabolizer for the cytochrome P450 CYP2D6 gene ∗ . DEA production was strongly inhibited (more than 80%) by the anti-P450 3A4 antibody, but not by anti-LKM1-positive serum. It seems therefore that the P450 3A subfamily is certainly implicated in human hepatic amiodarone N -deethylation.
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A simple, inexpensive approach is proposed for enhancing the durability of automotive proton exchange membrane fuel cells by selective promotion of the hydrogen oxidation reaction (HOR) and suppression of the oxygen reduction reaction (ORR) at the anode in startup/shutdown events. Dodecanethiol forms a self-assembled monolayer (SAM) on the surface of Pt particles, thus decreasing the number of Pt ensemble sites. Interestingly, by controlling the dodecanethiol concentration during SAM formation, the number of ensemble sites can be precisely optimized such that it is sufficient for the HOR but insufficient for the ORR. Thus, a Pt surface with an SAM of dodecanethiol clearly effects HOR-selective electrocatalysis. Clear HOR selectivity is demonstrated in unit cell tests with the actual membrane electrode assembly, as well as in an electrochemical three-electrode setup with a thin-film rotating disk electrode configuration.
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eng_Latn
| 31,532 |
Neurochemical evaluation of rats prenatally exposed to the adrenergic agonists clonidine and lofexidine.
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Clonidine (CLON), an alpha-2 adrenergic agonist, is widely used to reduce hypertension; it is also recommended for blocking acute opiate withdrawal. Lofexidine (LOF), a CLON analog, is an investigational compound being readied for the marketplace. Since exposure to both drugs is likely to occur in the last two trimesters of human pregnancy, it is important to determine whether such exposure can have effects upon brain or behavior of offspring. Pregnant CD rat dams were given daily subcutaneous injections of saline, CLON, or LOF on days 8 through 20 of gestation. Maternal weight during gestation, neonatal weight and neurochemical measures were monitored. Maternal body weight was reduced in a dose dependent manner. At PND 1 brain ornithine decarboxylase (ODC) activity was reduced in LOF- but not CLON-exposed pups of both sexes. At this age no alteration was seen in whole brain catecholamine levels or in whole brain alpha-2-adrenergic binding.
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Electrochemiluminescence (ECL)-functionalized metal–organic frameworks (MOFs) have attracted increasing attention in biosensing in virtue of their diverse and tunable optical properties. A famous ECL luminophore, carboxyl-rich tris(4,4′-dicarboxylic acid-2,2′-bipyridyl) ruthenium(II) (Ru(dcbpy)32+), possesses the characteristics of good water solubility and excellent ECL performance and also has the potential to be the organic ligand of metal–organic frameworks. Herein, functionalized MOF nanosheets (RuMOFNSs) containing plenty of Ru(dcbpy)32+ in the frameworks were synthesized in aqueous solution by a simple one-pot method. In this protocol, Ru(dcbpy)32+ acted as organic ligand to coordinate with Zn2+ originated from Zn(NO3)2, and polyvinylpyrrolidone (PVP) was used as structure-directing agent to control the formation of sheetlike structure. For practical application, a “signal-on” ECL immunosensor was designed for cardiac troponin I (cTnI) detection by employing RuMOFNSs as ECL probe. The immunosensor ...
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eng_Latn
| 31,533 |
Analytical chemistry of synthetic colorants
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X-ray powder diffraction of synthetic organic colorants. Solid state nuclear magnetic resonance spectroscopy of synthetic dyes. Near infrared spectroscopy. Mass spectrometry. Electron spin resonance spectroscopy. Microspectrophotometry. Emission spectroscopy. Identification and analysis of diarylide pigments by spectroscopic and chemical methods. Index.
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Abstract A new liquid chromatography detector has been developed with sensitivity to most organic compounds in the 10 – 100 picogram region, but insensitive to common eluents. Photons from a vacuum UV lamp ionize solutes in the vaporized LC column effluent, without ionizing the mobile phase. Initial studies of its performance and applications indicate considerable promise as a sensitive, universal detector.
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eng_Latn
| 31,534 |
Meso-aryl-ß-pyrrolic positions interactions in meso-tetraarylporphyrins: Flat arylporphyrins and building blocks for oligoporphyrins
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Aryl groups bound to the meso positions of porphyrins often react with neighboring groups, in particular s-acyl groups to give highly diversified monomeric and dimeric new functionalized porphyrins. The products, whose meso-aryl ring approaches coplanarity with the porphyrin macrocycle, show large shifts of UV-visible absorption bands and various potentialities for building external chelating moieties and assembling oligoporphyrins.
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Two new processor arrays for the 2D discrete Fourier transform are proposed. Both structural schemes are oriented towards VLSI technology. They can be used in the construction of high-throughput processors for multidimensional and fast Fourier transforms as well as triple matrix multiplication. The first structural scheme consists of two successively connected one-dimensional arrays of processor elements (PEs), and the second one represents a single array of more complex PEs. The advantages of these structural schemes are the localisation of all data exchanges between PEs and the absence of necessity of matrix transposition. >
|
eng_Latn
| 31,535 |
Characterization of the products formed in the reaction between 1,3-butadienemonoxide and 2′-deoxyadenosine by liquid chromatography—continuous-flow fast atom bombardment mass spectrometry
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1,3-Butadiene. a widely produced industrial chemical, has recently been identified as a strong rodent carcinogen. Butadiene is metabolized to reactive 3,4-epoxy-1-butene (BM), which may bind to DNA. The reaction between 3,4-epoxy-1-butene and 2'-deoxyadenosine (dAdo) was studied. The reaction was carried out in trifluoroethanol-triethylamine and the reaction mixture was analysed by liquid chromatography-continuous-flow fast atom bombardment mass spectrometry. The recorded total-ion chromatogram showed four peaks. The spectra of the peaks exhibited a protonated molecule of BM adducts of dAdo (m/z 322), indicating formation of different isomers of the adducts. One alkylation site was shown to be at the exocyclic amino group of the 2'-deoxyadenosine
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Highly active ketol-acid Li deokto iso isomerase enzyme and, in addition to the fermentation method of producing isobutanol is provided by the fermentation culture of recombinant micro-organisms expressing other enzymes required for the conversion of glucose to isobutanol. Gene, glucose, isobutanol, inactive, polypeptides, host cells
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eng_Latn
| 31,536 |
NICKEL(II), COPPER(II), ZINC(II), CADMIUM(II) AND MERCURY(II) COMPLEXES OF TRIS(2-AMINOETHYL)PHOSPHINE OXIDE
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Abstract New coordination compounds Ni(TEAPO)X2nH2O, Cu(TAEPO)(NO3)24H2O, Zn(TEA-PO)(N03)22H2O, Cd(TEAPO)(NO3)22H2O, Hg(TEAPO)Br22H2O (TAEPO = tris(2-aminoethyl)phosphine oxide, X=C1 or ClO4, n = 4 or 2) have been synthesized and characterized. As revealed by a single-crystal X-ray analysis of Cu(TAEPO)(NO3)2-4H2O, the Cu(II) ion has a distorted octahedral arrangement of donor atoms with a CuN3O3 chromophore. Tris(2-aminoethyl)phosphine oxide acts as a tetradentate donor forming a bridge among three adjacent copper(II) atoms in the cyclic-chain, polymeric structure. Each central atom is coordinated by three nitrogens and one oxygen from three TAEPO ligands in a square-planar geometry. The coordination geometry of Cu(II) is completed by weaker interactions with two water molecules [Cu-O = 2.461(5), 2.601(5) A]. The remaining water molecules and nitrate anions are not coordinated.
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The active-site CXXC motif of thiol:disulfide oxidoreductases is essential for their catalysis of redox reactions. Changing the XX residues can perturb the reduction potential of the active-site disulfide bond of the Escherichia coli enzymes thioredoxin (Trx; CGPC) and DsbA (CPHC). The reduction potential is correlated with the acidity of the N-terminal cysteine residue of the CXXC motif. As the pKa is lowered, the disulfide bond becomes more easy to reduce. A change in pKa can account fully for a change in reduction potential in well-characterized CXXC motifs of DsbA but not of Trx. Formal analysis of the Nernst equation reveals that reduction potential contains both pH-dependent and pH-independent components. Indeed, the difference between the reduction potentials of wild-type Trx and wild-type DsbA cannot be explained solely by differences in thiol pKa values. Structural data for thiol:disulfide oxidoreductases reveal no single factor that determines the pH-independent component of the reduction potent...
|
yue_Hant
| 31,537 |
Direct Observation of Conformational Isomers of (CH3S)2 Molecules on Cu (111)
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Scanning tunneling microscope (STM) images of isolated molecules of dimethyl disulfide, (CH3S)2, adsorbed on a Cu (111) surface were successfully obtained at a sample temperature of 4.7 K. A (CH3S)2 molecule appears as an elliptic protrusion in the STM images. The STM images of (CH3S)2 molecules revealed that the molecules have a total of six equivalent adsorption orientations on Cu (111), which are given by the combination of three equivalent adsorption sites and two conformational isomers for each adsorption site.
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We have used IR spectroscopy to study the reaction between L-cysteine and dimethyl sulfoxide in aqueous medium. We have found that reaction occurs with formation of an insoluble product, which we have identified. We show that oxidation of L-cysteine by dimethyl sulfoxide can occur at an appreciable rate under mild conditions, with formation of L-cystine, dimethyl sulfide, and water.
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eng_Latn
| 31,538 |
Synthesis andCrystal Structure of 2,7,7-Trimethyl-3-ethoxycarbonyl- 4-(3-nitrophenyl)-5-oxo-1,4,5,6,7,8-hexahydroquinoline under Microwave Irradiation
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The title compound (C21H24N2O5) has been synthesized by the reaction of 3-nitrobenzaldehyde, dimedone, ethyl acetoacetate and ammonium acetate under microwave irradiation without solvent and its structure was determined by single-crystal X-ray diffraction. The crystal is orthorhombic, space group Pbcn with a =17.953(3), b =15.206(4), c =14.299(3), V=3904(2)3, Z =8, Mr =384.42, Dc =1.308Mg/m3, ?(MoKα) =0.094cm-1, F(000) =1632. The structure was solved by direct methods and refined by full-matrix least-squares method to the final R=0.0493, wR =0.1078. X-ray analysis reveals that the prydine ring is of boat conformation and the six-membered ring fused with it is of envelope conformation.
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Abstract The chemical carcinogens 4-nitroquinoline 1-oxide (4-NQO) and 4-hydroxylaminoquinoline 1-oxide (4-HAQO) can induce single-strand breaks in the DNA of cultured Ehrlich ascites tumor cells. In cells incubated after treatment with these carcinogens most of the DNA fragments can be rejoined. This rejoining process may be related to the malignant transformation of normal cells by treatment in vitro with carcinogenic compounds.
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eng_Latn
| 31,539 |
Organosilanols as Catalysts in Asymmetric Aryl Transfer Reactions
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[reaction: see text] Various ferrocene-based organosilanols have been synthesized in four steps starting from achiral ferrocene carboxylic acid. Applying these novel planar-chiral ferrocenes as catalysts in asymmetric phenyl transfer reactions to substituted benzaldehydes afforded products with high enantiomeric excesses. The best result (91% ee) was achieved in the addition to p-chlorobenzaldehyde with organosilanol 2b, which has a tert-butyl substituent on the oxazoline ring and an isopropyl group on the silanol fragment.
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The article has investigated photocatalytic destruction of anionic SAS—sodium alkylbenzene sulfate (ABS) in the aqueous medium by ozone on TiO2 Degussa P-25 at UV radiation by a DB-15 low-pressure mercury-quartz lamp. The paper has determined the parameters of photocatalytic ozonization securing complete ABS destruction (100% in terms of organic carbon). We have assessed advantages of photocatalytic ozonization of ABS solutions compared with photocatalytic oxidation by oxygen and O3/UV treatment.
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eng_Latn
| 31,540 |
Inhibition of cyclooxygenase-2 activity in subchondral bone modifies a subtype of osteoarthritis
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Osteoarthritis (OA) causes the destruction of joints. Its pathogenesis is still under investigation, and there is no effective disease-modifying therapy. Here, we report that elevated cyclooxygenase-2 (COX-2) expression in the osteocytes of subchondral bone causes both spontaneous OA and rheumatoid arthritis (RA). The knockout of COX-2 in osteocytes or treatment with a COX-2 inhibitor effectively rescues the structure of subchondral bone and attenuates cartilage degeneration in spontaneous OA (STR/Ort) mice and tumor necrosis factor-α transgenic RA mice. Thus, elevated COX-2 expression in subchondral bone induces both OA-associated and RA-associated joint cartilage degeneration. The inhibition of COX-2 expression can potentially modify joint destruction in patients with arthritis.
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Removal of 137Cs+, one of the most hazardous radionuclides, from nuclear waste, is a challenging task because it requires simultaneously high capacity and high selectivity. Chalcogenides offer a great opportunity to design and create high-performance 137Cs+ absorbents. We report a new material (InSnOS) with facile ion-exchange properties. The anionic framework is based on corner-shared pseudo-T4 supertetrahedral oxysulfide [In8Sn12O10S34]16– clusters, resulting in the formula [In8Sn12O10S32]12–. The crystal structure features the interpenetration of two independent oxysulfide cluster frameworks which create pincer cavities based on sulfur atoms that prove highly effective for capturing Cs+ ions. The binding mode of the Cs+ ions by the material was determined by a single crystal structure refinement of a fully ion-exchanged single crystal. The structure determinations show that the small pores created by the two interpenetrating frameworks are the optimal size for capturing Cs+. This advantage makes the ma...
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eng_Latn
| 31,541 |
UV absorption cross-sections of cis-BrONO
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Abstract UV absorption cross-sections for cis -BrONO in the gas phase have been measured over the wavelength range 200–365 nm. Absorption measurements were made following cw photolysis of Br 2 in Br 2 /NO 2 /N 2 mixtures in a 100 cm long temperature-regulated absorption cell. The cis -BrONO absorption spectrum shows two maxima in this wavelength range: at 228 nm (2.7×10 −18 cm 2 molecule −1 ) and 316 (0.41×10 −18 cm 2 molecule −1 ). cis -BrONO absorption cross-sections were determined relative to BrNO 2 .
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Abstract The IR spectra of some halogenated symmetric derivatives of phenol in solid state are reported. The CNDO/2 method has been applied to calculate the V 2 torsional barrier; this method gives larger values than those obtained from other conventional methods. The origin of the tilt angle in phenols is discussed.
|
eng_Latn
| 31,542 |
Metabolic engineering strategies for acetoin and 2,3-butanediol production: advances and prospects
|
AbstractAcetoin and 2,3-butanediol (2,3-BD) have a large number of industrial applications. The production of acetoin and 2,3-BD has traditionally relied on oil supplies. Microbial production of acetoin and 2,3-BD will alleviate the dependence on oil. Acetoin and 2,3-BD are neighboring metabolites in the 2,3-BD metabolic pathway of bacteria. This review summarizes metabolic engineering strategies for improvement of microbial acetoin and 2,3-BD production. We also propose enhancements to current acetoin and 2,3-BD production strategies, by offering a metabolic engineering approach that is guided by systems biology and synthetic biology.
|
Abstract Ethylene dimerization has been studied by means of ab initio calculations using the STO-3G basis set. A transition state that presents a tricentric interaction has been found. The appearing of such structure is discussed and justified.
|
eng_Latn
| 31,543 |
“Click Chemistry” in Zeolites: Copper(I) Zeolites as New Heterogeneous and Ligand‐Free Catalysts for the Huisgen [3+2] Cycloaddition
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For the first time, copper(I)-exchanged zeolites were developed as catalysts in organic synthesis. These solid materials proved to be versatile and efficient heterogeneous, ligand-free catalytic systems for the Huisgen [3+2] cycloaddition. These cheap and easy-to-prepare catalysts exhibited a wide scope and compatibility with functional groups. They are very simple to use, easy to remove (by filtration), and are recyclable (up to three times without loss of activity). Investigations with deuterated alkynes and deuterated zeolites proved that this Cu I -zeolite-catalyzed "click" reaction exhibited a mechanism different from that reported for the Meldal-Sharpless version.
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A fluorescent chemosensor is a powerful analytical tool for the visualization and quantitation of analytes in living cells, tissue slices, and whole bodies. Peptides with a reporter ionophore are very valuable as fluorescent chemosensors, because of their higher biological compatibility and solubility compared to organic dyes, and they are more stable than proteins in aqueous solutions. Herein, we report a novel peptide fluorescent chemosensor (HL) based on tetra-peptides conjugated with dansyl groups, which was synthesized by solid phase peptide synthesis. This chemosensor selectively and sensitively detects Zn2+ based on the photo-induced electron transfer (PET) effect by turn-on response in 100% aqueous solutions. As designed, HL can penetrate live HeLa cells and image intracellular Zn2+ by turn-on response. Moreover, HL exhibits low biotoxicity with a limit of detection (LOD) of about 32 nM for Zn2+, implying that HL acts as a highly useful peptide fluorescent chemosensor for biological systems.
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eng_Latn
| 31,544 |
High-performance ion-exchange separation of oxidized and reduced nicotinamide adenine dinucleotides.
|
High-performance anion-exchange chromatography of oxidized and reduced forms of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) on a Pharmacia Mono Q anion-exchange column is reported. Microgram quantities of all four nucleotides can be separated at pH 7.7 in approximately 20 min. For preparative purposes, greater than 7 mg of NADH can be purified in a single injection, and the peak fractions have an A260 of greater than 80 OD units with an A260/A340 ratio of 2.25.
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Abstract A layer of random defects in the simple cubic Ising model with nearest neighbor ferromagnetic interactions of strength J is considered. Using the real space renormalization group method we calculate defect free energy in the whole temperature range. Specifically, we analyze: the layer of diluted defects, the layer of spin-glass type defects, and the layer of mixed defects. The free energy is strongly dependent on the value of couplings between the defect and the bulk.
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eng_Latn
| 31,545 |
Novel preparation of fluorinated isoindoles and their conversion to fluorinated benzoporphyrins
|
4,5,6,7-Tetrafluoroisoindole and their related compounds were prepared directly from the corresponding phthalonitriles by reduction of a hydride reagent such as DIBAL or catalytic hydrogenation in the presence of an acid. 4,5,6,7-Tetrafluoroisoindole was converted to fluorinated benzoporphyrins.
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The single-factor test and orthogonal design were applied for optimizing five factors in the ISSR-PCR reaction system including primers,Taq DNA polymerase,dNTPs,template DNA and annealing temperature to establish and optimize ISSR-PCR reaction system for Mahonia bealei.The suitable PCR reaction system contained 0.5 μmol/L primer,0.5 U Taq DNA,150 μmol/L dNTPs,and 20 ng template DNA in total 20 μL reaction solution.15 primers were screened from 80 ISSR primers with stable amplification and rich polymorphism.The ISSR reaction system was proved to be stable and credible in the test of 9 Mahonia bealei populations.This optimized ISSR reaction system would provide the basis for the genetic analysis of Mahonia bealei.
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eng_Latn
| 31,546 |
Facile activation of the C−I bond of primary alkyl halides by Pt(II) complexes having a benzothiazole ligand
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Abstract The alkyl halides, RI (MeI and EtI), were oxidatively added to a Pt(II) complex [PtMe2(pbt)], 1, in which pbt = 2-(2-pyridyl)benzothiazole, to give the Pt(IV) complexes [PtIRMe2(pbt)] (R = Me; 2 and R = Et; 3). Kinetics of the reactions in toluene and acetone were studied using UV-vis spectroscopy between 5 and 40 °C and an SN2 mechanism was suggested. The reaction of MeI with complex 1 was considerably faster than EtI. The reactions followed second-order kinetics, rate = k2 [1] [RI], and the rates in the polar solvent acetone were faster than those in the nonpolar solvent toluene. Activation parameters have been determined and large negative values for ΔS‡ were obtained. The results were also confirmed using DFT calculations. The computational investigations were used to determine the geometry of the species involved in the suggested mechanism and energy barriers.
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Objective To design and synthesis novel triazole antifungal derivatives and study the antifungal activity.Methods All the target compounds were prepared from 1,3- difluorobenzene via click reaction;The antibacterial activities of the title compounds were determined with broth dilution method.Results Twelve compounds were synthesized and characterized by 1H NMR and MS.All the title compounds exhibited potent antifungal activities against nearly all fungi tested.Conclusion The electronic effects of the substituents affected the activity of compounds,specifically the electron- donating groups.
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eng_Latn
| 31,547 |
[Grafting reaction of tetrabutyltin on the MCM-41 surface and characterization of the grafted product].
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MCM-41 modified with tetrabutyltin and Sn-O-MCM-41 obtained from calcination of the modified MCM-41 in pure oxygen were characterized by XRD, FTIR, UV-Vis DRS, and TG analysis. It was found that the hydrothermal stability, surface acidity, and coordinative states of tin atoms on both samples were evidently different. After calcination, the surface tin atoms of sample remained in the tetrahedronal structure, and the hydrothermal stability and surface acidity were improved. According to the results, the reason for the enhancement of catalytic activity of Sn-O-MCM-41 was discussed.
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AbstractAcetoin and 2,3-butanediol (2,3-BD) have a large number of industrial applications. The production of acetoin and 2,3-BD has traditionally relied on oil supplies. Microbial production of acetoin and 2,3-BD will alleviate the dependence on oil. Acetoin and 2,3-BD are neighboring metabolites in the 2,3-BD metabolic pathway of bacteria. This review summarizes metabolic engineering strategies for improvement of microbial acetoin and 2,3-BD production. We also propose enhancements to current acetoin and 2,3-BD production strategies, by offering a metabolic engineering approach that is guided by systems biology and synthetic biology.
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eng_Latn
| 31,548 |
A rapid and efficient entry to synthesis of quino and chromenocarbazoles via Ullmann-Goldberg condensation
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Abstract An efficient two-step method for the preparation of quino and chromenocarbazoles via Ullmann–Goldberg condensation of 3-aminocarbazole and 3-hydroxy-9-ethylcarbazole with o -halobenzoic acids followed by cyclization with POCl 3 has been described.
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SummaryThe metabolism of betahistine, demethylbetahistine and 2-(2-hydroxy-ethyl) pyridine in the rabbit leads to the urinary excretion of acidic metabolities, including 2-pyridylacetate, which is excreted in part as N-2-pyridylacetylglycine. Other unidentified Koenig-positive compounds were in the acidic fraction.
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eng_Latn
| 31,549 |
Effect of the structure and concentration of diphosphine ligands on the rate of hydrocarbomethoxylation of cyclohexene catalyzed by palladium acetate/diphosphine/TsOH system
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Abstract Cyclohexene hydrocarbomethoxylation catalyzed by the Pd(OAc) 2 – p-toluenesulfonic acid – diphosphine systems with broad variation of diphosphine structure and concentration was studied. It was shown that the hydrocarbon part of the structure and the mutual arrangement of the phosphine groups are the factors that control the activity of palladium-containing catalysts. By comparison of the promoting effects of mono and diphosphine ligands, it is demonstrated that bridging trans-diphosphines show higher efficiency with regard to both the kinetic (TOF) and concentration factors (low P/Pd ratios). In particular, their promoting activity is an order of magnitude higher than that for triphenylphosphine at lower P/Pd ratios (8–65 times). The results were interpreted from the standpoint of chelation effect and the geometric matching of the diphosphine structure to the arrangement of vacant s,d-orbitals of the Pd centre.
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This work deals with the analysis of the performance and emissions of ethanol HCCI/PSCCI engines by means of a Dynamic Adaptive Chemistry (DAC) technique. The implementation of such a technique provides a reduction of the computational cost of the simulations without compromising the reliability of the results. Very accurate results, in terms of pressure and heat release rate profiles and CO, CO2 and UHC emissions, are obtained with ethanol as the only species for the DRGEP graph search both with the charge uniformly distributed in the combustion chamber and by directly injecting liquid fuel in the same chamber. The global speed up of DAC simulations is twice with respect to a full mechanism which consists of 57 species and 288 reactions and a further increase is expected when DAC is compared to very detailed kinetics.Copyright © 2012 by ASME
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eng_Latn
| 31,550 |
A new synthetic technology of the anti-malarial drug lumefantrine
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Objective: To design a new synthetic technology of the anti-malarial drug lumefantrine.Methods: Industrial fluorine was used as starting material.In the presence of manganese dioxide and using glacial acetic acid as solvent,inletting hydrogen chloride gas and 2,7-dichlorofluorene were produced.Then,using anhydrous AlCl3 as catalyst,2,7-dichlorofluorene reacted with chloracetyl chloride to produce 2,7-dichloro-4-chloracetyl fluorene.Finally,the "one-pot reaction" was used for the reduction,amination and condensation reaction to obtain lumefantrine.Results and Conclusion: The total yield of this technology was over 40% based on fluorene,its processing steps were less than those of previous technologies,and the operation was simple.Thus,the new method is much more advanced and the new process route is much more suitable for industrial production.
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Our fluorescence study gave information on the presence of chemical defects and irregularities in crystal structure, offering a good tool for quality evaluation of organic crystalline materials. We have analyzed the correlation between the bulk or thin film samples' quality determined by experimental parameters (thermal gradient, moving speed of the growth interface, crucible configuration, slow or fast solidification rates) and the fluorescence characteristics for pure meta-dinitrobenzene and meta-dinitrobenzene doped with 8 hydroxyquinoline or 1.3 dihydroxybenzene. The comparative study of the position and shape of the fluorescence emissions for pure and controlled doped materials gave us information on the chemical defects.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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eng_Latn
| 31,551 |
Zooxanthellactone, a Novel γ-Lactone-type Oxylipine from Dinoflagellates of Symbiodinium sp : Structure, Distribution, and Biological Activity
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A novel fatty acid derivative named zooxanthellactone (ZL) was isolated from several strains of symbiotic microalgae, dinoflagellates of the genus Symbiodinium. The metabolite is structurally related to docosahexaenoic acid (DHA) and seems to be biosynthesized by oxidation and subsequent lactonization. The absolute stereochemistry was determined from the specific rotation of the perhydro derivative. The distribution of ZL within several Symbiodinium isolates was quantitatively analyzed by HPLC techniques and suggested a relationship between the productivity of this metabolite and the Symbiodinium phylogeny. The cytotoxicity of ZL was evaluated by using human squamous cell carcinoma cell lines in comparison with that of DHA and other common fatty acids, suggesting that the long unsaturated chain was important rather than the γ-lactone moiety.
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Zeolite-based catalysts have been widely used in the conversion of biomass recently, but the catalytic yields of the desired products are strongly limited by the relatively small micropores of zeolite. Here, we reported a hierarchically porous ZSM-5 zeolite with micropore and b-axis-aligned mesopore-supported Ru nanoparticles (Ru/HZSM-5-OM) that are highly efficient for the hydrodeoxygenation of both small and bulky phenolic biomolecules to the corresponding alkanes. Compared with the conventional ZSM-5 zeolite-supported Ru catalyst, the high catalytic activities and alkane selectivities over Ru/HZSM-5-OM are attributed to the abundant exposed acidic sites in HZSM-5-OM with open mesopores. This feature is potentially important for future phenolic bio-oil upgrading.
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eng_Latn
| 31,552 |
New 1,2-Dihydropyridine-Based Fluorophores and Their Applications as Fluorescent Probes
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New 1,2-dihydropyridine (1,2-DHP)-based fluorophores 1a-1h were designed and synthesized by a one-pot four-component condensation reaction using dienaminodioate, aldehydes, and an in situ-generated hydrazone mediated by trifluoroacetic acid. The photophysical properties of 1,2-DHPs were studied in detail, and a few of them exhibited selective mitochondrial staining ability in HeLa cell lines (cervical cancer cells). A detailed photophysical investigation led to the design of 1,2-DHP 1h as an optimal fluorophore suitable for its potential application as a small molecule probe in the aqueous medium. Also, 1,2-DHP 1h exhibited sixfold enhanced emission intensity than its phosphorylated analogue 1h' in the long wavelength region (λem ≈ 600 nm), which makes 1,2-DHP 1h' meet the requirement as a bioprobe for protein tyrosine phosphatases, shown in L6 muscle cell lysate.
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Partial 16S rRNA gene sequence comparisons have been used to determine the phylogenetic placement of the Elbe River isolate RW1, the first described bacterium capable of complete mineralization of dibenzo-p-dioxin. Sequence similarities, cluster analysis and signature positions demonstrate that RW1 groups with other species of Sphingomonas as a distinct, new species of this genus.
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eng_Latn
| 31,553 |
Semiempirical molecular orbital calculations on octahedral aquo complexes of transition metal ions: σ-donor ability of water
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A comparative analysis is carried out on the strengths of binding of a series of transition metal ions to a water molecule using CNDO type MO theory developed earlier. Comparative features of the energetics of metal-ligand bonds in aquo and amine complexes are also analyzed.
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Quantum dots consisting of a cadmium selenide core encapsulated in a shell of cadmium doped zinc sulfide have the potential to revolutionize fluorescent imaging of live cell cultures. In order to utilize these fluorescent probes it is necessary to functionalize them with biologically active ligands. In this paper we report the design and synthesis of a ligand that has a high affinity for the serotonin transporter (SERT) that may be conjugated to quantum dots.
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eng_Latn
| 31,554 |
Cytotoxic and anti-inflammatory activities of phenanthrenes from the medullae of Juncus effusus L.
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Bioactivity guided phytochemical investigation of the ethanol extract of the medullae of Juncus effusus resulted in the isolation of two new phenanthrenes, 8-hydroxymethyl-2-hydroxyl-1-methyl-5-vinyl-9,10-dihydrophenanthrene (1), and 5-(1-methoxyethyl)-1-methyl-phenanthren-2,7-diol (2) together with 15 known phenanthrenoids (3–17). The chemical structures of 1 and 2 were established by a combination of spectroscopic techniques. Compounds 1–15 and 17 were evaluated for their cytotoxic activities against five human cancer cell lines (SHSY-5Y, SMMC-7721, HepG-2, Hela and MCF-7) by CCK-8 assay, and their anti-inflammatory activities were also evaluated by inhibition on NO production in LPS-activated murine macrophage RAW 264.7 cells.
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Anharmonic correlated Debye model has been derived for calculation and analysis of extended X-ray absorption fine structure (EXAFS) cumulants using an anharmonic effective potential that takes into account all nearest neighbor interactions of absorber and backscattering atoms. Dispersion relation has been considered, and anharmonic effects are included based on cumulant expansion. Analytical expressions for the first, second, third, and fourth EXAFS cumulants have been derived. They contain anharmonic effective potential parameters. Numerical calculations have been applied to Cu, where Morse potential is used to characterize the interaction between each pair of atoms. The results are found to be in good agreement with experiment.
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eng_Latn
| 31,555 |
Efficient synthesis of 2-imino-1,2-dihydroquinolines and 2-imino-thiochromenes via copper-catalyzed domino reaction
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A domino approach to 2-imino-1,2-dihydroquinolines and 2-imino-thiochromenes from sulfonyl azides, alkynes, and 2-acyl anilines or the potassium salt of 2-mercapto-benzaldehyde has been developed. This one-pot method is efficient and versatile.
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Thermodynamic considerations were done to interpret the vapor growth mechanisms of CuInS2 layers on GaP substrates. The transport rate (QcuIns2 ) and GaP etchiog cooceotsatioo were computed. The transport rate of CuInS2 at fixed reaction temperatures peaks at a certain iodine concentration. At fixed source temperature and iodine concentration, QcuIns2 increases with the temperature difference between the source and the substrate (ΔT). Computational results of varying Tsource, Tsubstrate, and ΔT are included in this paper. The thermodynamic calculations provide accounts for the substrate etching. Furthermore, the transport rate is computed when nonstoichiometric materials are used as the source.
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eng_Latn
| 31,556 |
Teneur en lipides de halophytes et resistance au sel Lipid Contents of Halophytic Plants and Salt-resistance
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Summary The study of five halophytic species showed that shoots lipid contents were similar or varied slightly with salt-tolerance. However it seemed that fatty acid composition and salt-resistance degree of each one of these species were related. The most salt-tolerant species ( Halocnemum strobilaceum and Arthrocnemum indicum ) showed the lowest linolenic acid level (34,4% and 39,7% respectively). In less salt-resistant species, linolenic acid level remained always higher than 50 % of total fatty acids. As for linoleic acid percentage, it increased with degree of salt tolerance: 25,4 % for Salicornia arabica and 32,6 % for Halocnemum strobilaceum .
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Transient receptor potential vanilloid (TRPV) channels are activated by ligands and heat and are involved in various physiological processes. In contrast to the architecturally related voltage-gated cation channels, TRPV1 and TRPV2 subtypes possess another activation gate at the selectivity filter that can open widely enough to permeate large organic cations. Despite recent structural advances, the mechanism of selectivity filter gating and permeation for both metal ions and large molecules by TRPV1 or TRPV2 is not well known. Here, we determined two crystal structures of rabbit TRPV2 in its Ca2+-bound and resiniferatoxin (RTx)- and Ca2+-bound forms, to 3.9 A and 3.1 A, respectively. Notably, our structures show that RTx binding leads to two-fold symmetric opening of the selectivity filter of TRPV2 that is wide enough for large organic cation permeation. Combined with functional characterizations, our studies reveal a structural basis for permeation of Ca2+ and large organic cations in TRPV2.
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eng_Latn
| 31,557 |
Switching the selectivity of the photoreduction reaction of carbon dioxide by controlling the band structure of a g-C3N4 photocatalyst
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The selectivity of the CO2 photoreduction reaction in the presence of water vapour can be modulated by the band structure of a g-C3N4 photocatalyst. The major products obtained using bulk g-C3N4 with a bandgap of 2.77 eV and g-C3N4 nanosheets with a bandgap of 2.97 eV are acetaldehyde (CH3CHO) and methane (CH4), respectively.
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A hypothesis that low molecular weight aromatic compounds, which occur naturally in the soil, may act as alternative substrates or inducers for the 2,4-dichlorophenoxyacetate (2,4-D) degrading enzyme system of an Arthrobacter sp. and maintain this enzyme system in the absence of 2,4-D, was examined experimentally. In a nonmanometric resting cell experiment, the 2,4-D adapted Arthrobacter sp. rapidly degraded 6 of the 12 aromatic compounds tested, and these 6 compounds were tested further with 2 additional aromatic compounds in manometric experiments with 2,4-D grown and citrate-grown cells. Homogentisic acid and catechol were oxidized more rapidly by 2,4-D grown cells than by cells grown on citrate medium. Thus, these two compounds could serve as alternative substrates for the 2,4-D degrading enzyme system of the Arthrobacter sp. In further manometric experiments, the 2,4-D degrading enzyme system in cells adapted to 2,4-dichlorophenol, catechol, or sodium benzoate was not induced.
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eng_Latn
| 31,558 |
Detection of Clostridium botulinum Type C Cells in the Gastrointestinal Tracts of Mozambique Tilapia (Oreochromis mossambicus) by Polymerase Chain Reaction
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We established a method of directly detecting Clostridium botulinum type C cells, while minimizing spore detection, in the intestinal contents of Mozambique tilapia (Oreochromis mossambicus). This technique involved extraction of predominantly cellular DNA from tilapia intestinal tracts and used a polymerase chain reaction assay to detect presence of type C1 toxin gene. We consistently detected C. botulinum type C cells in tilapia gastrointestinal contents at a level of 7.5 x 104 cells per 0.25 g material or 1.9 x 103 cells. This technique is useful for determining prevalence of the potentially active organisms within a given population of fish and may be adapted to other types of C. botulinum and vertebrate populations as well.
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Abstract This review deals with the reaction mechanisms of polyaminecarboxylate complexes of different transition metals such as Fe, Mn, Ni, and Ru. Three types of chemical processes are treated, viz. water-exchange reactions, the binding of NO, and the activation of peroxides. In each case, the nature of the polyaminecarboxylate chelate and its influence on the underlying reaction mechanism are considered. In general, the complexes are either six- or seven-coordinate and all contain a coordinated water molecule. The lability of the latter is controlled by the nature of the polyaminecarboxylate chelate and the oxidation state of the metal ion. The binding of NO and the activation of peroxide are in turn controlled by the lability of the coordinated water molecule that is displaced during the interaction with these small molecules.
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eng_Latn
| 31,559 |
Solvent-free synthesis of functionalized 5-imino-2,5-dihydrofurans from isocyanides, activated acetylenes and alkyl cyanoformates
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The reaction between alkyl(aryl) isocyanides, dialkyl acetylenedicarboxylates and alkyl cyanoformates under solvent-free conditions leads to dialkyl 2-cyano-5-alkyl(aryl)imino-2-alkoxy-2,5-dihydrofuran-3,4-dicarboxylates in high yields.
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We have used IR spectroscopy to study the reaction between L-cysteine and dimethyl sulfoxide in aqueous medium. We have found that reaction occurs with formation of an insoluble product, which we have identified. We show that oxidation of L-cysteine by dimethyl sulfoxide can occur at an appreciable rate under mild conditions, with formation of L-cystine, dimethyl sulfide, and water.
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eng_Latn
| 31,560 |
Atomic Absorption Determination of Certain Sulfonamides via Their Metal Complexes
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Abstract An atomic absorption spectroscopic (A.A.S.) method for microdetermination of sulfathiazole, sulfadiazine and sulfamerazine has been developed. The procedure is based upon the measurement of the metal content of the sulfur metal chelate. The experimental conditions as well as the molar ratios are thoroughly studied. The percentage recoveries for the 3 compounds tested were found to be 99.5 ± 1.30, 99.7 ± 0.80 and 100.6 ± 0.78, respectively. The proposed method was applied to some pharmaceutical preparations of common occurrence and the results were satisfactory and in good agreement with those given by complexometric and diazometric ones.
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Related Article: Gummadi Durgaprasad, Javier A. Luna, Kyle D. Spielvogel, Christian Haas, Scott K. Shaw, Scott R. Daly|2017|Organometallics|36|4020|doi:10.1021/acs.organomet.7b00623
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eng_Latn
| 31,561 |
Condensed heterocycles. 48. Benzo[b]furan mercapto- and selenolaldehydes in the synthesis of bifunctional and complex-forming compounds
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2-Bromo-3-benzo[b]furaldehyde and 3-chloro-2-benzo[b]furaldehyde react with sodium hydrosulfide or hydroselenide to give isomeric mercapto- and selenolbenzo furaldehydes, which afford the S (or Se) alkyl derivatives on reaction with ethyl chloroacetate, and Schiff bases on reaction with ethylenediamine hydrochloride. In the presence of sodium ethoxide, the S- and Sealkylated mercapto- and selenolaldehydes cyclize to thieno- and selenobenzofurans, while the Schiff bases afford chelate complexes with nickel and copper acetates.
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We have shown that de novo designed peptides self-assemble in the presence of copper to create supramolecular assemblies capable of carrying out the oxidation of dimethoxyphenol in the presence of dioxygen. Formation of the supramolecular assembly, which is akin to a protein fold, is critical for productive catalysis since peptides possessing the same functional groups but lacking the ability to self-assemble do not catalyze substrate oxidation. The ease with which we have discovered robust and productive oxygen activation catalysts suggests that these prion-like assemblies might have served as intermediates in the evolution of enzymatic function and opens the path for the development of new catalyst nanomaterials.
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eng_Latn
| 31,562 |
Secondary structure and topology of a mitochondrial presequence peptide associated with negatively charged micelles. A 2D H-NMR study.
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In this study the secondary structure and topology of the peptide, corresponding to the presequence of cytochrome oxidase subunit IV (p25) in a negatively charged membrane-mimetic environment, were assessed by circular dichroism and two-dimensional nuclear magnetic resonance. The micelles used consisted of dodecylphosphoglycol (DPG), a mild anionic detergent with a headgroup resembling that of phosphatidylglycerol. The secondary structure was analyzed by interresidue nuclear Overhauser enhancement measurements and chemical shifts of backbone protons. The data revealed α-helix formation of the peptide upon interaction with the micelles, both in the N- and in the C-terminal halves, which are separated from each other by the proline residue at position 13. The topology of the peptide was studied by determining the effect of spin-labeled 12-doxylstearate on the line widths of the peptide proton resonances. This method revealed the insertion of hydrophobic residues of both the N- and the C-terminal halves of p...
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Substitution of selenium for sulfur in the cathode of a rechargeable battery containing Sx molecules in microporous slits in carbon allows a better characterization of the electrochemical reactions that occur. Paired with a metallic lithium anode, the Sex chains are converted to Li2Se in a single-step reaction. With a sodium anode, a sequential chemical reaction is characterized by a continuous chain shortening of Sex upon initial discharge before completing the reduction to Na2Se; on charge, the reconstituted Sex molecules retain a smaller x value than the original Sex chain molecule. In both cases, the Se molecules remain almost completely confined to the micropore slits to give a long cycle life.
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eng_Latn
| 31,563 |
ChemInform Abstract: A Novel Intermolecular Synthesis of γ-Lactones via Visible-Light Photoredox Catalysis.
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Hydroxyalkylation of aromatic alkenes and following transesterification allows the direct γ-lactone formation via a light promoted photoredox reaction in the presence of an Ir-catalyst.
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Objective: To design a new synthetic technology of the anti-malarial drug lumefantrine.Methods: Industrial fluorine was used as starting material.In the presence of manganese dioxide and using glacial acetic acid as solvent,inletting hydrogen chloride gas and 2,7-dichlorofluorene were produced.Then,using anhydrous AlCl3 as catalyst,2,7-dichlorofluorene reacted with chloracetyl chloride to produce 2,7-dichloro-4-chloracetyl fluorene.Finally,the "one-pot reaction" was used for the reduction,amination and condensation reaction to obtain lumefantrine.Results and Conclusion: The total yield of this technology was over 40% based on fluorene,its processing steps were less than those of previous technologies,and the operation was simple.Thus,the new method is much more advanced and the new process route is much more suitable for industrial production.
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eng_Latn
| 31,564 |
Characterization of a Perfluorotetradecahydrophenanthrene Oligomer
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A complex mixture of oligomeric perfluorocarbons was characterized primarily by nuclear magnetic resonance spectroscopy, electron spectroscopy for chemical analysis, and time-of-flight secondary ion mass spectrometry. Supporting tools were infrared and ultraviolet/visible spectrometry, plus elemental analysis and conventional gas chromatography/mass spectrometry. The following distribution of carbon and fluorine groups (expressed as the percentage of total carbons) was determined : olefinic carbon, 8% ; CF 3 , 8% ; CF 2 , 51% ; and CF, 33%. A general structural framework is proposed with the chemical formula C 14 F 23 (C 14 F 22 ) n C 14 F 23 , where n = 0, 1, and 2 for dimer, trimer, and tetramer, respectively. The monomer has the structure of perfluorotetradecahydrophenanthrene. A wide diversity of structures was created during synthesis by (1) loss of fluorine atom pairs to create further ring closure or unsaturated carbon-carbon bonds and (2) ring opening to obtained perfluoroalkyl side chains.
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This work discusses the nature and significance of molecular, ultrastructural, and behavioural characters that can be used in phylogenetic analyses of rotifers.
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eng_Latn
| 31,565 |
Glucocorticoid activity and structure activity relationships in a series of some novel 17 alpha-ether-substituted steroids: influence of 17 alpha-substituents.
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A series of non-fluorinated glucocorticoids, cortienic acid analogs with a 17 beta-chloromethyl ester and various 17 alpha-ether functions, were tested for their affinity to the rat-lung type-II glucocorticoid receptor. The relative binding affinity of a set of 9 compounds was determined in a competitive experiment with [1,2,4-3H]triamcinolone acetonide. The highest binding affinities were observed with the 17 alpha-propoxy and butoxy analogs which were 1.3 times more active than the standard dexamethasone. Quantitative analysis of the results suggested that steric factors and lipophilicity of the side-chain were the major parameters affecting receptor affinity. Representative members of the series were compared to betamethasone 17 alpha-valerate in a vasonstriction test. The results paralleled those of the receptor binding experiment, indicating that the new steroids have good skin-permeation properties and good glucocorticoid activity.
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Abstract Cluster-based coordination frameworks superior to single metal-ion based coordination frameworks possess highly connected nets, large porous channels and enhanced stability. The carbonate anion (CO32−), an excellent anion template, can also serve as a rigid ligand with planar triangular geometry. It is an effective means of utilizing renewable carbon resources by the fixation of atmospheric carbon dioxide. Therefore, pursuing complex functional cluster-based coordination framework materials bridging by CO32− ligand is a sensible idea. Herein, compound {[Ag34(SBut)16(CF3COO)10(CO3)5(H2O)4][Et3N+]2}n (1) (Ag17S8 dimer) consists of a [Ag17(SBut)8(CF3COO)6(CO3)]+ cationic secondary building unit (SBU), a [Ag17(SBut)8(CF3COO)4(CO3)3(H2O)4]− anionic SBU and a bridging CO32− ligand in an asymmetric unit, which is extended into a 2D honeycomb network parallel to the bc plane with a simple topology symbol of {63}. Compound 1 has been well defined and the luminescence properties of 1 have been investigated.
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eng_Latn
| 31,566 |
Poly(Schiff's bases)-bifluorophores : Synthesis, photophysical properties, non-radiative energy transfer of electronic excitation
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The method of synthesis of unsymmetrical azomethynes-bifluorophores where one of the fluorescent fragments is a donor of electron excitation energy and the second one is an acceptor was worked out. Photophysical properties of azomethynes-bifluorophores were investigated. It was shown that in these compounds non-radiative energy transfer takes place. It was established that quantum-chemical semiempirical method AMI may be used for the calculation of spatial structure of amines-fluorophores.
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Microwave Photonics, a symbiotic field of research that brings together the worlds of optics and radio frequency is currently facing several challenges in its transition from a niche to a truly widespread technology essential to support the ever-increasing values for speed, bandwidth, processing capability and dynamic range that will be required in next generation hybrid access networks. We outline these challenges, which are the subject of the contributions to this focus issue.
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eng_Latn
| 31,567 |
Superluminal optical solitons in a four-level tripod atomic system
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With one weak probe field and two strong pumping fields, superluminal optical solitons are formed in a lifetime-broadened four-level tripod atomic medium. With proper parameters, both dark and bright solitons can occur in the highly resonant medium. The corresponding group velocity of the solitons can be superluminal. Meanwhile, the conditions for superluminal solitons occurrence are given.
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ConspectusThe axioms of stereoelectronic theory constitute an atlas to navigate the contours of molecular space. All too rarely lauded, the advent and development of stereoelectronic theory has been one of organic chemistry’s greatest triumphs. Inevitably, however, in the absence of a comprehensive treatise, many of the field’s pioneers do not receive the veneration that they merit. Rather their legacies are the stereoelectronic pillars that persist in teaching and research. This ubiquity continues to afford practitioners of organic chemistry with an abundance of opportunities for creative endeavor in reaction design, in conceiving novel activation modes, in preorganizing intermediates, or in stabilizing productive transition states and products. Antipodal to steric governance, which mitigates destabilizing nonbonding interactions, stereoelectronic control allows well-defined, often complementary, conformations to be populated. Indeed, the prevalence of stabilizing hyperconjugative interactions in biosynt...
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eng_Latn
| 31,568 |
Process Development of the Sharpless Catalytic Asymmetric Dihydroxylation Reaction To Prepare Methyl (2R,3S)-2,3-Dihydroxy-3-phenylpropionate
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A typical Sharpless catalytic asymmetric dihydroxylation (ADH) process to make methyl (2R,3S)-2,3-dihydroxy-3 phenylpropionate has been successfully developed. The ADH reaction was exothermic and complete in 2−3 h without affecting the optical purity and yield. The major impurity of methyl (2R)-hydroxy-3-keto-phenylpropionate, which may seriously damage the quality of diol, has been identified and removed properly in the process.
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The article has investigated photocatalytic destruction of anionic SAS—sodium alkylbenzene sulfate (ABS) in the aqueous medium by ozone on TiO2 Degussa P-25 at UV radiation by a DB-15 low-pressure mercury-quartz lamp. The paper has determined the parameters of photocatalytic ozonization securing complete ABS destruction (100% in terms of organic carbon). We have assessed advantages of photocatalytic ozonization of ABS solutions compared with photocatalytic oxidation by oxygen and O3/UV treatment.
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eng_Latn
| 31,569 |
Discovery of new benzensulfonamide derivatives as tripedal STAT3 inhibitors
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Abstract Persistent activated STAT3 has a striking correlation with cancer development and inhibition of STAT3 signaling pathway is a novel therapeutic way for human cancers. Among STAT family, STAT1 and STAT3 play opposite roles in tumorigenesis. However, the discovery of selective STAT3 inhibitors is still challenging to date. In this study, a series of small-molecular (MW
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In this paper, 8 thiosemicarbazones and 12 transition metal complexes thereof have been synthesized and tested for bacteriostatic activity against five kinds of bacteria. The results show that hetero atom or substitution group in the o-position of the aryl ring to the carbonyl group in the aldehyde or ketone is essential to the bacteriostatic activity of the thiosemicarbazones, and different mechanisms of inhibition are followed by thiosemicarbazones and their complexes. The complexes displayed activity superior to the thiosemicarbazones.
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eng_Latn
| 31,570 |
Absence of Epstein-Barr virus carrying cells in synovial membranes and subcutaneous nodules of patients with rheumatoid arthritis.
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OBJECTIVES--To determine whether the Epstein-Barr virus is present in synovial membranes and subcutaneous nodules of patients with rheumatoid arthritis. METHODS--A sensitive in situ hybridisation technique was applied to tissue sections of 11 synovial membranes and five rheumatoid nodules. RESULTS--Cells carrying the Epstein-Barr virus were not detected using EBER and BHLF1 oligonucleotides in the tissue samples investigated here. CONCLUSIONS--Although it has been suggested that the Epstein-Barr virus could play a part in the aetiology of rheumatoid arthritis, it was not detected in synovial membranes and subcutaneous lesions in this study.
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Abstract A new cyano-bridged dimeric oxo-centered triruthenium complex [{Ru 3 (μ 3 -O)(μ-CH 3 COO) 6 (py) 2 }(μ-CN){Ru 3 (μ 3 -O)(μ-CH 3 COO) 6 (py)(L py-SS )}] + (py = pyridine, L py-SS = (C 5 H 4 N–CH 2 NHC(O)(CH 2 ) 4 CH(CH 2 ) 2 SS) ([ 1 ] + ) has been prepared, characterized, and confined on an Au(1 1 1) surface to form self-assembled monolayers (SAMs) ( 1/Au ). The redox and IR spectroscopic properties observed for the discrete ions are essentially preserved in its SAMs. The molecules of SAMs 1/Au stand up with the cyano groups tilted to the gold surface. The electronic structures of 1/Au in different oxidation states have been studied by in situ infrared spectroscopy monitoring the stretching modes of the cyano group. The extent of cyano-mediated electronic communications between two triruthenium units in the SAMs has been successfully tuned by simply changing the electrolyte solutions from 0.1 M n -Bu 4 NPF 6 –CH 2 Cl 2 to aqueous 0.1 M HClO 4 .
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eng_Latn
| 31,571 |
Photochromic properties of some N-substituted 3,3-dimethyl-6′-nitroindoline-2-spiro-2′-2H-chromenes
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A number of photochromic 1-carbethoxymethyl-3,3-dimethyl-6′-nitroindoline-2-spiro-2′-2H-chromenes were synthesized. The introduction of a carbethoxymethyl substituent at the nitrogen atom instead of a methyl group somewhat increases the rate of dark decolorization of the photomerocyanines without appreciably affecting the spectral characteristics. The results are compared with the analogous spectral-kinetic characteristics of 1-phenyl-substituted compounds.
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Equations have been developed for describing the isotherms of extraction of rare-earth metal(III) [REM(III)] nitrates from aqueous concentrated solutions by 100% diisoamyl methylphosphonate, taking into account the variation of activity coefficients of components in the organic phase when its composition is varied within broad limits. The thermodynamic parameters of the extraction equilibria have been calculated using as the standard states hypothetical one-molal aqueous REM(III) nitrate solutions and pure components of the organic phase at a mole fraction of 1.0.
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eng_Latn
| 31,572 |
Synthesis and characterization of a luminescent Ni(II)-compound based on tpt and m-H2bdc detecting picric acid and chromate anions in aqueous
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Abstract A new luminescent compound Ni4(tpt)4(m-bdc)4·H2O (1) (tpt = tris(4-pyridyl)triazine, m-H2bdc = m-benzenedicarboxylic acid) was successfully synthesized by hydrothermal method, and characterized using single-crystal X-ray diffraction, PXRD, TG analysis and IR. 1 possesses a four-connected three-dimensional (3D) topological network with the Schlafli symbols of {65⋅8}. 1 not only has excellent thermal and chemical stability, but also is a dual-functional luminescent sensor with high selectivity and sensitivity for detection of picric acid (PA) and chromate (CrO42−) anions in water via the luminescent quenching. And the sensing mechanism for the quenching process was discussed in detail. Moreover, 1 can be regenerated by a fast and simple method in detecting PA and CrO42−, showing excellent recyclability after the sensing experiment.
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TiCl((OPr)-Pr-i)(3) and NaBH(OAc)(3): an efficient reagent combination for the reductive amination of aldehydes by electron-deficient amines Sodium triacetoxyborohydride, NaBH(OAC)(3) with tri- isopropoxytitanium chloride, TiCl((OPr)-Pr-i)(3) is a useful reagent combination for reductive amination. Electron-deficient amines and heteroaromatic amines such as 2-aminopyrimidine and 2-aminothiazole can be reductively alkylated at room temperature to afford the corresponding secondary amines in good yields. © 2005 Elsevier Ltd. All rights reserved.
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eng_Latn
| 31,573 |
Synthesis and Structure–Activity Relationship Studies of Furan-ring Fused Chalcones as Antiproliferative Agents
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As part of our continuing investigation of flavonoid derivatives as potential anticancer substances, the synthesis of 25 cinnamoyl derivatives of benzofuran as furan-fused chalcones was carried-out and these compounds were further evaluated for their antiproliferative activity towards HL60 promyelocytic leukemia cells. In comparison with 2',4'-dihydroxychalcone, attachment of a furan moiety on the A-ring enhanced activity by more than twofold. Benzofurans may be useful in the design of biologically active flavonoids.
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The present invention is directed to a process for preparing a cellular polyurethane by reacting with an NCO-reactive component in the presence of a homogeneous mixture of an optionally water-containing adduct of carbon dioxide an amine containing at least one secondary amino group, low primary amino groups and at least one primary or secondary hydroxyl group (provided there are not more primary hydroxyl groups than amino groups), an amine catalyst and optionally monofluorotrichlormethane. The present invention is directed to the homogeneous mixture these three components.
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eng_Latn
| 31,574 |
Equivalent effects of nicardipine and captopril on urinary albumin excretion of type 2, non-insulin-dependent diabetic subjects with mild to moderate hypertension.
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To test if calcium antagonists and converting enzyme inhibitors can act similarly on urinary albumin excretion of type 2, non-insulin-dependent diabetic subjects with hypertension, a 24 week, double-blind, randomized, parallel multicentre study was performed in 111 such patients allocated to nicardipine 50 mg slow release form (n = 57) or to captopril 25 mg (n = 54) twice daily. The efficacy of both drugs was similar on urinary albumin excretion (Westlake test p = 0.19). However, blood pressure was lower on nicardipine than on captopril (p < 0.05), and the antialbuminuric effect of nicardipine was related to its hypotensive effect, while this was not the case for captopril. The two drugs were tolerated equally. Thus, nicardipine and captopril for 24 weeks can be equally effective on urinary albumin excretion of type 2, non-insulin-dependent diabetic subjects with hypertension, but the mechanisms of their anti-albuminuric effects may be different.
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A new combined approach of using layered double hydroxides (LDHs) for both environmental remediation and the derived material as heterogeneous catalyst for selective oxidation is presented. A series of CoAl LDHs with carbonate or nitrate anion in the interlayers was synthesized by two different methods, namely, constant-pH precipitation using NaOH as precipitating agent and homogeneous precipitation by hexamine hydrolysis. The samples were optimized for chromate removal and an uptake of 45 mg Cr/g was obtained for CoAl2-N (CoAl-LDH with Co/Al atomic ratio of 2 and nitrate as interlayer anion by constant-pH precipitation) which was significantly higher than its corresponding carbonate sample that showed 15 mg Cr/g. The thus derived materials after uptake of chromate were explored for solvent free selective oxidation of benzyl alcohol using tert-butyl hydroperoxide as oxidant at room temperature. Among the catalysts screened, CoAl2-N sample after chromate uptake gave 23% conversion with 100% selectivity for...
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eng_Latn
| 31,575 |
Hypocapnia enhances the pressor effect of phenylephrine during isoflurane anesthesia in monkeys.
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Phenylephrine was administered to increase arterial blood pressure in 6 monkeys anesthetized with isoflurane during both normocapnia (arterial partial pressure of CO2 35 to 44 mm Hg) and hypocapnia (arterial partial pressure of CO2 23 to 29 mm Hg). The doses of phenylephrine required to increase mean blood pressure to 33% and 66% above control pressure during hypocapnia [1.7+/-0.9 and 3.1+/-1.7 microg/kg/min (mean+/-SD), respectively] were significantly less than the doses required to achieve the same changes in blood pressure during normocapnia (2.4+/-0.9 and 4.9+/-2.4 microg/kg/min, respectively, P<0.05). In patients with intracranial pathology, for whom hypocapnia is frequently induced, phenylephrine dosage may need to be appropriately reduced.
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Tandem mass spectrometry was used to explore the trends in the unimolecular fragmentation of the ionized hydroxy-substituted polycyclic aromatic hydrocarbons 1-naphthol, 9-hydroxyphenanthrene and 1-hydroxypyrene. The main dissociation reactions across all ring systems were CO- and HCO-loss, with ionized 1-naphthol also losing H atoms. Both ionized 1-naphthol and 9-hydroxyphenanthrene displayed the sequential loss of C2H2 and C4H2 from the [M-HCO]+ ions, reminiscent of unsubstituted PAH ions. CO-loss is slightly favored for 1-naphthol and 9-hydroxyphenanthrene at low collision energy, but less so for 1-hydroxypyrene. Reaction mechanisms for HCO- and CO-losses from 1-hydroxypyrene were derived from CCSD/6-31G(d)//B3-LYP/6-31G(d) calculations. The CO-loss mechanism is dominated by two transition states, TS-A governing a 1,3-H shift in the molecular ion, and TS-C which governs a ring-closing step to form a five-member ring in the product ion. HCO-loss occurs over a much flatter potential energy surface with t...
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eng_Latn
| 31,576 |
2-Chloro-6-[(4-hydroxy-3,5-dimethoxybenzyl)amino]-9-isopropylpurine
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The structure of the title compound, C17H20ClN5O3, consists of discrete molecules of a 6-(benzylamino)purine derivative. The secondary structure is stabilized by N—H⋯O hydrogen bonds connecting molecules into centrosymmetric dimers and by weak interatomic contacts of the types C—H⋯Cl and C—H⋯O, and by π–π stacking interactions.
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Abstract Exposure of the dorsal skin of hairless mice to the light of a germicidal lamp under standardized conditions produces reproducible, time-dependent increases of putrescine and spermidine concentrations, and a decrease of spermine levels, concomitant with the increase of the rate of DNa synthesis. Systemic or topical treatment of the animals with α-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, completely prevents the uv light-induced rapid formation of putrescine, and diminishes the enhancement of polyamine turnover rates. A significant effect of the drug on the rate of DNA synthesis could not be shown. The model is suitable for the study of interrelations between polyamine metabolism and cell proliferation and for the screening of compounds designed as inhibitors of polyamine biosynthesis.
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eng_Latn
| 31,577 |
The serology of Newcastle virus infection. II. The antigenic relationships of Newcastle virus.
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Summary 1.Cross-neutralization tests were done with chicken and rabbit antisera, prepared against 3 strains of Newcastle virus and against a strain of mumps and of swine influenza virus. All 3 strains of Newcastle virus produced antisera effective against each other. 2.Both chicken and rabbit antisera against mumps failed to neutralize Newcastle virus. 3.Chicken antisera to Newcastle virus failed to neutralize mumps virus; but rabbit antisera prepared to the 3 strains of Newcastle gave inconsistent results against mumps and the possible relation of Newcastle and mumps viruses under this condition is being further tested. 4.Several human sera with high titers of neutralization antibodies against Newcastle were successfully absorbed with mumps virus. The absorption was successful particularly when a dilution of the serum was used, and includes 1 serum which had a low titer of neutralization against mumps itself.
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Studies on the relative reactivities of esters of oncogenic and nononcogenic members of the purine N-oxide series indicate that, despite similarities in rates of reaction with the solvent, electrophilic cations from oncogenic derivatives are 10- to 100-fold more reactive toward added nucleophiles in vitro than are cations from nononcogenic compounds. The studies provide strong confirmation of an earlier proposal that nitrenium ion contributors of delocalized aromatic cations from 3-acyloxypurines, rather than radical intermediates, are the agents responsible for the oxidizing reactivity of these esters. They demonstrate further that delocalized aromatic nitrenium ions are highly susceptible to reduction by common nucleophiles that are not usually associated with oxidation-reduction reactions. Examples of such behavior with "soft" bases and other oncogenic arylamines indicate the generality of this little recognized property of aromatic nitrenium ions.
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eng_Latn
| 31,578 |
Improved histochemical method of demonstrating open capillaries
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A modification of Pickworth's method for demonstrating open capillaries is described. The distinguishing feature of this method is freezing the organ in situ with liquid propane, cooled with liquid nitrogen, followed by lyophilization of the specimen and fixation with gaseous formaldehyde. The sections are stained strictly in accordance with Pickworth's method.
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Abstract Literature sources on metal-organic materials encapsulating versatile porphyrinoids and heme enzymes have been discussed in this review. General fundamentals and structural and chemical requisites of these architectures are discussed in introduction followed by historical perspectives of the initial composites. We have categorized the structural aspects of this class of compounds according to the host and guest skeletons as well as encapsulating strategies in a sequential manner. Heme mimetic, as well as some novel applications of the materials including oxidation, electron transfer, carbene transfer and bio-molecule sensing, are then discussed and compared with each other and their homogeneous analogues based on mechanistic similarities, wherever possible.
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eng_Latn
| 31,579 |
The primary water splitting light reaction. Mass spectrometric determination of gaseous hydrogen and oxygen evolution from water photolysis by platinized chlorophyll a dihydrate polycrystals
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Mass spectrometric analyses of the light-induced products from various mixtures of H/sub 2//sup 16/O, D/sub 2//sup 16/O, and H/sub 2//sup 18/O were compared with those of electrolyzed samples (30nA passed for ten minutes using a platinized Pt foil) containing the corresponding isotopic water mixtures. An energy storage efficiency of 0.04% was obtained for an observed rate of about 10/sup -3/ mol/hr of water photolysis using 10/sup 17/ chlorophyll a molecules. The authors estimate that <1% of the light was effectively engaged in the photoreaction, but expect that there is the possibility of enhancing the energy efficiency by two orders of magnitude. They conclude that the splitting of water observed in their studies is attributable to the intrinsic properties of the chlorophyll a, but there is evidence that the platinum itself may be partially responsible.
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We developed to produce optically pure glycerol derivatives, such as (R) and (S)-2, 3- dichloro-1-prop-anols, and (R) and (S)-3-chloro-1, 2-propanediols, based on microbial resolution. These compounds are precursors of optically active epichlorohydrins and glycidols which are used for wide variety of organic syntheses. We describe here the new methods to obtain these chiral C3 units and their several synthetic applications.
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eng_Latn
| 31,580 |
Intramolecular excited state charge transfer and fluorescence decay of p-cyano-N,N-dimethylaniline in mixed hydrocarbon/halocarbon solvents
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Abstract Fluorescence spectra, quantum yields and lifetimes of p-cyano-N,N-dimethylaniline (CDMA) were studied in various binary mixtures of n -hexane with chlorinated hydrocarbons. Solvent effects on the equilibrium between normal emission and fluorescence originating from the highly dipolar twisted internal charge transfer (TICT) state arise predominantly from non-specific solute-solvent interactions. The non-radiative deactivation rate of the TICT state is affected primarily by the solvent composition and slows down with the stabilization of the TICT state in environments of high polarity.
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A method of manufacturing a strongly adherent coating on an inorganic or organic base, on a) an inorganic or organic base, low-temperature plasma treatment, subjected to corona discharge treatment or flame treatment, b) on the inorganic or organic substrate, one more photoinitiators or mixtures of photoinitiators with monomers or / and oligomers containing at least one ethylenically unsaturated group, or solutions of the above materials, applying the suspension or emulsion, and optionally, c) using suitable methods, or dry these foregoing materials, and the method of irradiating with / or electromagnetic waves, the formula (I), (II), (III) and / or (IV): IN-L-RG (I) , IN-L-RG 1 -L 1 -H (II), IN-L-RG 1 -L 1 -IN 1 (III), IN-L-RG 1 -L 1 - , Monoacyl phosphine, be a mono-acylphosphine oxide or monoacylphosphine sulfide photoinitiator group; L, L
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eng_Latn
| 31,581 |
Bacteremia Caused by Linezolid-Resistant Enterococcus faecium in Liverpool, United Kingdom
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Linezolid is an effective antimicrobial agent for treating infections caused by vancomycin-resistant enterococci (VRE). More than 99.4% of all Enterococcus faecium isolates are susceptible to linezolid (1). We describe a case of bacteremia caused by a linezolid-resistant E. faecium strain that developed while treating a patient with an intra-abdominal infection. Linezolid acts at the peptidyltransferaseactive site at the 50S ribosome, blocking aminoacyl-tRNA binding and thereby preventing translation initiation. The most common mechanism for linezolid resistance in enterococci is the G2576T mutation, leading to G2576U alteration in domain V of the 23S rRNA, altering the drug’s binding site (2). We performed PCR on our patient’s VRE blood culture isolates to determine the presence of the mutational resistance mechanism, and we determined drug penetration levels into the site of infection by measuring the linezolid concentrations in samples of pancreatic fluid.
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Iron complexes of the tetradentate ligand, bis(2,5-dihydroxyacetophenone) ethylenediamine, and a fifth anionic ligand have been prepared and characterized by spectroscopic techniques. E.p.r. studies of the X-band frozen DMF solution reveal the presence of a broad, g ca. 4.0, signal with weak features at lower fields. The complexes exhibit a broad visible band with λmax in the 550–605 nm range which is assigned to the phenolate → Fe charge transfer transition. The LMCT band energy varies with the anionic ligand, namely, N 3 - > Bz- > HCOO- > Cl- > ClO 4 - (Bz- = benzimidazole anion), similar to the behaviour of dioxygenases and proteins containing tyrosine coordinated to iron.
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eng_Latn
| 31,582 |
Synthesis and biological activity of N-acylmethyl derivatives of 9H-2,3-dihydroimidazo-and 10H-2,3,4,10-tetrahydropyrimido[1,2-a]benzimidazoles and their reduction products
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A series of N-acylmethyl derivatives of 9H-2,3-dihydroimidazo-and 10H-2,3,4,10-tetrahydropyrimido[1,2-a]benzimidazoles and products of their reduction has been synthesized and their pharmacological properties have been studied. Most of the synthesized substances possess weak antioxidant activity. At the same time, they exhibit pronounced antiaggregant and hemorheological properties, possess spasmolytic activity, and influence the blood glucose level.
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In this laboratory experiment, upper-division undergraduate chemistry and biochemistry majors investigate amide-bond-forming reactions from a green chemistry perspective. Using hydrocinnamic acid and benzylamine as reactants, students perform three types of amide-forming reactions: an acid chloride derivative route; a coupling reagent promoted method; and a boric acid catalyzed condensation. After isolation of the common product, students assess the reactions using the 12 Principles of Green Chemistry and several green chemistry metrics: atom economy; reaction mass efficiency; process mass intensity; and the EcoScale. In addition to assessing what route is the greenest, students also compare the metrics to discern what aspects of green chemistry each metric captures. In order to extend sustainability to economic considerations, the projected “front-end” cost of synthesizing a kilogram of the amide is calculated based on data from each reaction. The experimental work is conducted over two 3 h laboratory pe...
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eng_Latn
| 31,583 |
Mössbauer Spectra of Various Organic Iron Chelates
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Continuing our previous studies of the Mossbauer spectra of inorganic iron compounds, we have found some characteristic features of the spectra of some organic iron compounds. There is a general tendency, in a series of related compounds, for the isomer shift and the quadrupole splitting to increase regularly with increase in the structural complexity of the compounds. The data for iron(III) acetate, benzoate and salicylate suggest the polynuclear structure of these compounds. The observed isomer shifts for other organic iron compounds may also be interpreted in terms of the chemical binding in the molecule. No resonance absorption was observed for a few groups of organic iron chelates (1,3 diketone derivatives, etc.). Though our interpretation is still conjectual, the reason for this is believed to rest in the high recoil probability of these compounds.
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Related Article: Gummadi Durgaprasad, Javier A. Luna, Kyle D. Spielvogel, Christian Haas, Scott K. Shaw, Scott R. Daly|2017|Organometallics|36|4020|doi:10.1021/acs.organomet.7b00623
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eng_Latn
| 31,584 |
Purine Nucleoside Analogs. 12. Synthesis of Novel 8,9-Disubstituted Guanine Derivatives by S-Alkylation of 2-Acetamido-9-(2-acetoxyethoxymethyl)-6-oxo-8-thioxopurine
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S-Alkylation of 2-acetamido-9-(2-acetoxyethoxymethyl)-6-oxo-8-thioxopurine was used to synthesize its novel S- and N(7)-substituted derivatives. We have established the effect of the structure of the alkylating agent on the reaction conditions and its regioselectivity. We have shown that the synthesized guanine derivatives can be modified further.
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Diethylpyrocarbonate treatment of the neutral endopeptidase (EC 3.4.24.11) inhibits both catalytic activity and binding of the inhibitor [3H]-N(R,S)-3-hydroxyaminocarbonyl-2-benzyl-1-oxopropyl]-glycine. The loss of activity can be reversed by hydroxylamine and almost completely prevented by the competitive inhibitor phenylalanyl-leucine suggesting the presence, as in thermolysin, of a histidine residue at the active site. Butanedione treatment also reduces both catalytic activity and [3H] inhibitor binding. Phenylalanyl-leucine completely protects from the butanedione induced loss of activity, providing further evidence for an essential arginine at the active site. In contrast, the tyrosine modifying agent N-acetylimidazole has no apparent effect on enzyme activity.
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eng_Latn
| 31,585 |
The First Synthesis of Stilbene Dendrimers and their Photochemical trans–cis Isomerization
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Highly branched stilbene dendrimers underwent trans–cis isomerization in the excited singlet state within the lifetime of 10 ns.
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Abstract Ethylene dimerization has been studied by means of ab initio calculations using the STO-3G basis set. A transition state that presents a tricentric interaction has been found. The appearing of such structure is discussed and justified.
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eng_Latn
| 31,586 |
Theoretical and experimental studies of the dissociation dynamics of methaniminium cation, CH2NH2+→CHNH++H2: Reaction path bifurcation
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The unimolecular dissociation of CH2NH2+ has been investigated experimentally and theoretically. Kinetic energy release distribution was obtained by analyzing the mass-analyzed ion kinetic energy profile. Critical configurations along the reaction path were investigated by electronic structure calculations at the HF, MP2, QCISD, and B3LYP levels using the 6-31G** and 6-311+G** basis sets. Reaction path bifurcation was observed at all the levels. The bifurcation point was in the entrance region (before the transition state) at the HF level. This point moved to the exit region when the electron correlation effect was included at the MP2, QCISD, and B3LYP levels. A global potential energy surface incorporating this bifurcation feature was constructed by interpolation at the MP2/6-311+G** level. Classical trajectories were calculated on this surface and product mode-specific energies were evaluated. Based on these data, various experimental observations, lack of hydrogen scrambling in particular, could be ade...
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Abstract By varying the conditions of reacting methylhistamine, histamine, histidine, 3-methylhistidine, 1-methylhistidine, methylimidazoleacetic acid, and imidazoleacetic acid with NBS and OPD, fluorophors are obtained which could be exploited for the measurement of these substances in biological material.
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eng_Latn
| 31,587 |
Structure of acid-stable carmine.
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Acid-stable carmine has recently been distributed in the U.S. market because of its good acid stability, but it is not permitted in Japan. We analyzed and determined the structure of the major pigment in acid-stable carmine, in order to establish an analytical method for it. Carminic acid was transformed into a different type of pigment, named acid-stable carmine, through amination when heated in ammonia solution. The features of the structure were clarified using a model compound, purpurin, in which the orientation of hydroxyl groups on the A ring of the anthraquinone skeleton is the same as that of carminic acid. By spectroscopic means and the synthesis of acid-stable carmine and purpurin derivatives, the structure of the major pigment in acid-stable carmine was established as 4-aminocarminic acid, a novel compound.
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This chapter contains a tabular compilation of molecular constants of calcium fluoride at different quantum state.
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eng_Latn
| 31,588 |
Nitrogen-15 nuclear magnetic resonance spectra of isocyanates, isothiocyanates andN-sulfinylamines
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The ^(15)N NMR spectra of ten isocyanates, four isothiocyanates, and four N-sulfinylamines have been obtained at the natural-abundance level by high-resolution NMR spectroscopy. The results show that isocyanates and isothiocyanates have ^(15)N chemical shifts over 200 ppm toward higher fields compared to those of N-sulfinylamines. The sensitivity of the ^(15)N shifts in these substances to substituent and electronic effects are discussed.
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In this paper, a modeling and simulation method for planar interdigitated ruthenium oxide MEMS supercapacitor was proposed based on the electrochemical reaction mechanism of supercapacitor. The study simulated the planar interdigitated ruthenium oxide MEMS super capacitor using Comsol software. The highly accurate charge and discharge curves of the super capacitor, electric potential distribution graph and the concentration distribution graph were got through simulation. The effects of two structure-parameters were discussed in the research.
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eng_Latn
| 31,589 |
Thermodynamic parameters of activation for photodegradation of phenolics
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Abstract The photocatalytic degradation of three phenolics namely phenol, 4-chlorophenol and 4-nitrophenol were carried out in aerated aqueous suspension of TiO 2 irradiated by ultraviolet light. The influence of temperature at optimized pH and TiO 2 concentration was studied. The degradation kinetics were somewhat accelerated by increase in temperature in the range 25–45 °C and apparent activation energy was calculated to be 9.68–21.44 kJ mol −1 . Thermodynamic parameters of activation were also assessed for the degradation process. Formation of acidic species results in decrease in pH of solution. The appearance and the evolution of main intermediate species like hydroquinone, benzoquinone and catechol during the degradation process were computed by UV–vis spectral analysis.
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In this paper, the method of phosphate surfactant is introduced and the product is similar to natural lecithin in property. The optimum technological conditions : reaction temperature; 120℃, time: 5h, rate: n (ether); n (pocl3) =2. 9: 1
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eng_Latn
| 31,590 |
Matching the nanoporous carbon electrodes and organic electrolytes in double layer capacitors
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In order to see how the power density of supercapacitors could be increased, a theoretical model of the nanoporous carbon electrode as a tier structure with transport channels has been developed. Also an experimental method has been developed to measure the rate of electrolyte transport through the porous electrode material. This method can be used for quick analysis and selection of electrodes. The results of modeling have been verified by testing the experimental EDLC prototypes with optimum electrode thickness and electrode porosity, the porosity being well matched with the size of ions in organic electrolytes. This enables us to reach a power density as high as 6–7 kW/L with a reasonably large energy density and high efficiency for both EDLC unit cells and stacks.
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A hypothesis that low molecular weight aromatic compounds, which occur naturally in the soil, may act as alternative substrates or inducers for the 2,4-dichlorophenoxyacetate (2,4-D) degrading enzyme system of an Arthrobacter sp. and maintain this enzyme system in the absence of 2,4-D, was examined experimentally. In a nonmanometric resting cell experiment, the 2,4-D adapted Arthrobacter sp. rapidly degraded 6 of the 12 aromatic compounds tested, and these 6 compounds were tested further with 2 additional aromatic compounds in manometric experiments with 2,4-D grown and citrate-grown cells. Homogentisic acid and catechol were oxidized more rapidly by 2,4-D grown cells than by cells grown on citrate medium. Thus, these two compounds could serve as alternative substrates for the 2,4-D degrading enzyme system of the Arthrobacter sp. In further manometric experiments, the 2,4-D degrading enzyme system in cells adapted to 2,4-dichlorophenol, catechol, or sodium benzoate was not induced.
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eng_Latn
| 31,591 |
Theoretical Investigation of the Selective CC Hydrogenation of Unsaturated Aldehydes Catalyzed by [{RuCl2(mtppms)2}2] in Acidic Media
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Density functional theory has been applied to identify possible reaction intermediates for the catalytic C=C hydrogenation of cinnamaldehyde, which occurs in acidic aqueous solutions in the presence of water-soluble ruthenium phosphine complexes. On the basis of ONIOM calculations, two different active species and, hence, two pathways were proposed. The C=C bond hydrogenation takes place through the insertion of the terminal carbon atom into the Ru-H bond and subsequent protonation of the other carbon by hydroxonium ions present in the solution. We find that water is directly involved in several steps of the reaction, either as a protonating/deprotonating agent or as a coordinating ligand. Selectivity against C=O hydrogenation is due to the much higher barrier of either C insertion or O insertion into the Ru-H bond as compared to that of the C insertion in the case of the C=C functionality.
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Abstract The four hemicellulose fractions of timothy hay showed an increase in the ratio of pentose molecules per uronic acid molecule with the increase in alkalinity of the solvent required to extract them. A summative analysis of the constituents of timothy hay was made.
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eng_Latn
| 31,592 |
Ruthenium catalyzed desymmetrization of diazabicyclic olefins to access heteroaryl substituted cyclopentenes through C–H activation of phenylazoles
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Abstract The first ruthenium catalyzed redox-neutral C–H activation strategy for the ring-opening of diazabicyclic olefins via C–H bond cleavage of phenyl azoles is reported. The developed method offers a novel route to functionalized cyclopentenes by employing less-expensive ruthenium catalyst and readily accessible biologically significant heteroarenes. The present protocol is a merger of the C–H activation of phenyl substituted heteroaromatics and subsequent β-nitrogen elimination of diazabicyclic olefins.
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1. The syntheses and properties of 7-acetoxymethylbenz[a]anthracene 5,6-oxide, 7-hydroxymethylbenz[a]anthracene 5,6-oxide and trans-5,6-dihydro-5,6-dihydroxy-7-hydroxymethylbenz[a]anthracene are described.2. 7-Hydroxymethylbenz[a]anthracene 5,6-oxide was converted by rat-liver microsomal preparations and homogenates into trans-5,6-dihydro-5,6-dihydroxy-7-hydroxymethylbenz[a]anthracene and by rat-liver soluble fraction and glutathione, or by rat-liver homogenates, into a glutathione conjugate. Small amounts of 5-hydroxy-7-hydroxymethylbenz[a]anthracene were sometimes formed in these incubations, probably by a non-enzymic reaction.3. 7-Hydroxymethylbenz[a]anthracene was metabolized by rat liver microsomes into a number of products including the trans-5,6-dihydrodiol. This product was not detected when the hydroxymethyl derivative was incubated with rat liver homogenate.4. 7-Hydroxymethylbenz[a]anthracene 5,6-oxide was less efficient in alkylating 4-(p-nitrobenzyl)pyridine than 7-methylbenz[a]anthracene 5,6-...
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eng_Latn
| 31,593 |
Hydrogen Bond Assisted Activation of a Dinitrile Towards Nucleophilic Attack.
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Dinitrile (I) is used as convenient starting compound for the preparation of derivatives (II), (IV), (VI), (VIII), and (X).
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Features of the interaction with DNA of photoactivable aryl azides having various substituents in the aromatic ring have been studied. The nature of the interaction with DNA and the degree of its modification depend substantially on the nature of these substituents. The results obtained can be used for obtaining DNA probes bearing various marker groups.
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eng_Latn
| 31,594 |
P-NITROBENZYLOXYMETHYL : A NEW FLUORIDE-REMOVABLE PROTECTING GROUP FOR RIBONUCLEOSIDE 2'-HYDROXYLS
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Abstract A novel protecting group for the 2′-hydroxyl of ribonucleosides, p -nitrobenzyloxymethyl, is used in the rapid solid phase synthesis of the oligonucleotide U(U) 11 U; it can be readily removed from the oligomer product by treatment with tetrabutylammonium fluoride.
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The lift-off processes of BP212 positive photoresist(and chlorobenzene treatment) and AZP4620 positive photoresist(and chlorobenzene treatment) were studied.AZ5214E image-reversal photoresist was also studied.Side wall graphics were observed using scanning electron microscope(SEM).The forming mechanism of different lateral wall pattern was analysed.The optimum process parameters were found and used in metal lift-off in RF MEMS switches.
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yue_Hant
| 31,595 |
A new synthesis of 3(2H)-furanones from acetylenic β-diketones †
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Thermal cyclization of 1,5-diarylpent-1-yne-3,5-diones led to the formation of 2-benzyliden-5-aryl-3(2H) furanones as well as 2,6-diaryl-4H-pyran-4-ones as minor products. The structure of the furanones was established from their ir, 1H nmr and mass spectral data. Their reaction with hydrazine hydrate gave pyrazole derivatives.
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Abstract Exposure of the dorsal skin of hairless mice to the light of a germicidal lamp under standardized conditions produces reproducible, time-dependent increases of putrescine and spermidine concentrations, and a decrease of spermine levels, concomitant with the increase of the rate of DNa synthesis. Systemic or topical treatment of the animals with α-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, completely prevents the uv light-induced rapid formation of putrescine, and diminishes the enhancement of polyamine turnover rates. A significant effect of the drug on the rate of DNA synthesis could not be shown. The model is suitable for the study of interrelations between polyamine metabolism and cell proliferation and for the screening of compounds designed as inhibitors of polyamine biosynthesis.
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eng_Latn
| 31,596 |
Silver catalyst for obtaining formaldehyde
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FIELD: chemistry. SUBSTANCE: invention relates to field of catalyst. Described is method of obtaining silver crystals with distribution of average size of particles from 0.15 mm to 2.5 mm and porous coating of oxide materials in which a) silver crystals contact with sol-gel solution of said materials, in solvent, which contains organic solvent and b) obtained as a result silver crystals are collected, c) released from organic solvent and d) then subjected to thermal processing at temperature between 50°C and point of silver melting. Described is application of obtained crystals as catalyst for obtaining formaldehyde. EFFECT: increased activity of catalyst for obtaining formaldehyde. 10 cl, 3 dwg, 4 tbl, 1 ex
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Abstract Exposure of the dorsal skin of hairless mice to the light of a germicidal lamp under standardized conditions produces reproducible, time-dependent increases of putrescine and spermidine concentrations, and a decrease of spermine levels, concomitant with the increase of the rate of DNa synthesis. Systemic or topical treatment of the animals with α-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, completely prevents the uv light-induced rapid formation of putrescine, and diminishes the enhancement of polyamine turnover rates. A significant effect of the drug on the rate of DNA synthesis could not be shown. The model is suitable for the study of interrelations between polyamine metabolism and cell proliferation and for the screening of compounds designed as inhibitors of polyamine biosynthesis.
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eng_Latn
| 31,597 |
Caryophyllene driven diversity in an one-pot rearrangement of oxidation and transanular reactions
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Abstract Diversity oriented synthesis starting from natural products is a newly coming strategy to build diverse skeletons to meet the demands of high throughput screening in drug development. Caryophyllene was being considered as an ideal starting point to build divers natural-like sesquiterpenes due to its rich sources and build-in reactivity. In this paper, six new natural-like products (2–7) were synthesized form the natural cryophyllene oxide via cascade oxidation and transannular reactions in a one-pot procedure. Their structures were elucidated by exhaustive spectra method including 2D NMR and X-ray diffraction. Of the products, compounds 6 and 7 possess very similar skeleton to natural products. Our findings demonstrated that one-pot cascade reactions on macrocyclic natural products is a concise strategy to create diverse natural-like skeletons.
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Biaryl ethers were recently reported as potent NNRTIs. Herein, we disclose a detailed effort to modify the previously reported compound 1. We have designed and synthesized a series of novel pyrazole derivatives as a surrogate for pyrazolopyridine motif that were potent inhibitors of HIV-1 RT with nanomolar intrinsic activity on the WT and key mutant enzymes and potent antiviral activity in infected cells.
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eng_Latn
| 31,598 |
KBr-assisted synthesis of Cd_(0.5)Zn_(0.5)S solid solution photocatalyst and its visible-light activity for hydrogen evolution
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Cd0.5Zn0.5S solid solution photocatalysts were synthesized by a hydrothermal method assisted by the KBr.The products were characterized by XRD,SEM,UV-Vis absorption spectrometry、BET and fluorescence spectra.Their photoactivities were evaluated by hydrogen evolution from water under visible light(λ≥420nm)irradiation.It is found that the presence of KBr promotes the growth of ZnS(111)crystal facet in Cd0.5Zn0.5S solid solution and reduces nonradiative transition of the catalyst,thus the visible light photocatalytic activity of Cd0.5Zn0.5S are enhanced.
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The active-site CXXC motif of thiol:disulfide oxidoreductases is essential for their catalysis of redox reactions. Changing the XX residues can perturb the reduction potential of the active-site disulfide bond of the Escherichia coli enzymes thioredoxin (Trx; CGPC) and DsbA (CPHC). The reduction potential is correlated with the acidity of the N-terminal cysteine residue of the CXXC motif. As the pKa is lowered, the disulfide bond becomes more easy to reduce. A change in pKa can account fully for a change in reduction potential in well-characterized CXXC motifs of DsbA but not of Trx. Formal analysis of the Nernst equation reveals that reduction potential contains both pH-dependent and pH-independent components. Indeed, the difference between the reduction potentials of wild-type Trx and wild-type DsbA cannot be explained solely by differences in thiol pKa values. Structural data for thiol:disulfide oxidoreductases reveal no single factor that determines the pH-independent component of the reduction potent...
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eng_Latn
| 31,599 |
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