排序方式: 共有140条查询结果,搜索用时 140 毫秒
51.
Amrita Sarkar 《Journal of luminescence》2011,131(8):1731-45
Optical response of a novel dye has been studied in various media like neat and mixed binary solvents, aqueous SDS micelles and β-cyclodextrin (β-CD) nanocavities. Fluorescence parameters in pure and mixed binary solvents have been found to be sensitive to the nature of the microenvironment. The emitting state of the dye in protic solvent is different from that in aprotic solvents. In presence of cations (H+, Mg2+), the dye exists in two tautomeric forms at equilibrium in solution. The values of the equilibrium constant (K) and ΔH0 have been measured. Values of local dielectric constant (ε) and microviscosity (η) at the region of solubilisation of the dye in aqueous SDS micellar media have been found out. The dye has also been found to form complex with β-CD. The equilibrium constant and the energy of maximum fluorescence of the dye encapsulated by β-CD have been determined. 相似文献
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Hazra AB Han Y Chatterjee A Zhang Y Lai RY Ealick SE Begley TP 《Journal of the American Chemical Society》2011,133(24):9311-9319
In many bacteria tenI is found clustered with genes involved in thiamin thiazole biosynthesis. However, while TenI shows high sequence similarity with thiamin phosphate synthase, the purified protein has no thiamin phosphate synthase activity, and the role of this enzyme in thiamin biosynthesis remains unknown. In this contribution, we identify the function of TenI as a thiazole tautomerase, describe the structure of the enzyme complexed with its reaction product, identify the substrates phosphate and histidine 122 as the acid/base residues involved in catalysis, and propose a mechanism for the reaction. The identification of the function of TenI completes the identification of all of the enzymes needed for thiamin biosynthesis by the major bacterial pathway. 相似文献
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Cioci G Srivastava A Loganathan D Mason SA Pérez S Imberty A 《Journal of the American Chemical Society》2011,133(26):10042-10045
The biological addition of oligosaccharide moieties to asparagine residues of N-glycoproteins influences the properties and bioactivities of these macromolecules. The low-temperature neutron crystal structures of three N-glycoprotein linkage models and analogues provide accurate characterization of the three-dimensional structure of the conserved GlcNAc-Asn linkage. These first crystal structures of N-acetylated carbohydrates obtained by neutron diffraction provide high-resolution geometrical parameters that can be used for force-field parametrization and subsequent molecular dynamics simulation of N-glycoproteins. The correct localization of hydrogen atoms demonstrates the occurrence of trifurcated hydrogen bonds and hydrophobic contacts. 相似文献
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Dinabandhu Naskar Subhasish Neogi Amrita Roy Ashis Baran Mandal 《Tetrahedron letters》2008,49(48):6762-6764
Indoles can serve as substrates for the Petasis boronic acid-Mannich reaction, providing a practical synthetic route for C-C bond formation in α-(N-substituted indole)carboxylic acids. The scope and limitations of this method have been examined. 相似文献
55.
The complex [RuIII(edta)(H2O)]? (edta4? = ethylenediaminetetraacetate) catalyzes the oxidation of captopril (CapSH) using primary oxidants, hydrogen peroxide (H2O2) and peroxomonosulfate (\( {\text{HSO}}_{5}^{ - } \)). The kinetics of the oxidation reaction were studied as a function of both oxidant (H2O2, \( {\text{HSO}}_{5}^{ - } \)) and substrate (CapSH) concentrations using stopped-flow and rapid scan stopped-flow techniques. Spectral and kinetic data are suggestive of a pathway involving rapid formation of the intermediate complex [RuIII(edta)(CapS)]2? followed by direct attack of the oxidant (H2O2 or \( {\text{HSO}}_{5}^{ - } \)) at the S atom of the coordinated CapS?. ESI–MS and HPLC analysis of the reaction products showed that captopril disulfide (CapSSCap) is the major oxidation product. A probable mechanism in agreement with the spectral and kinetic data is presented. 相似文献
56.
Prakash Amrita Dhara Mishra R. K. Valsala T. P. Sharma V. Acharya R. Tyagi A. K. Pujari P. K. Kaushik C. P. 《Journal of Radioanalytical and Nuclear Chemistry》2021,328(2):519-526
Journal of Radioanalytical and Nuclear Chemistry - An attempt was made to increase the solubility of High Level liquid Waste (HLW), mainly Cr and Mo, by addition of P2O5 to sodium borosilicate... 相似文献
57.
Green's function approach to study the propagation of SH‐wave in piezoelectric layer influenced by a point source 下载免费PDF全文
Abhishek Kumar Singh Amrita Das Kshitish Ch. Mistri Amares Chattopadhyay 《Mathematical Methods in the Applied Sciences》2017,40(13):4771-4784
Green's function technique serves as a powerful tool to find the particle displacements due to SH‐wave propagation in layer of a shape different from the space between two parallel planes. Therefore, the present paper undertook to study the propagation of SH‐wave in a transversely isotropic piezoelectric layer under the influence of a point source and overlying a heterogeneous substrate using Green's function technique. The coupled electromechanical field equations are solved with the aid of Green's function technique. Expression for displacements in both layer and substrate, scalar potential and finally the dispersion relation is obtained analytically for the case when wave propagates along the direction of layering. Numerical computations are carried out and demonstrated with the aid of graphs for six different piezoelectric materials namely PZT‐5H ceramics, Barium titanate (BaTiO3) ceramics, Silicon dioxide (SiO2) glass, Borosilicate glass, Cobalt Iron Oxide (CoFe2O4), and Aluminum Nitride (AlN). The effects of heterogeneity, piezoelectric and dielectric constants on the dispersion curve are highlighted. Moreover, comparative study is carried out taking the phase velocity for different piezoelectric materials on one hand and isotropic case on the other. Dispersion relation is reduced to well‐known classical Love wave equation with a view to illuminate the authenticity of problem. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
58.
Basak A Roy SK Das S Hazra AB Ghosh SC Jha S 《Chemical communications (Cambridge, England)》2007,(6):622-624
The spontaneous activation of a nonaromatic enediynyl azide under ambient conditions has been demonstrated. The aromatic enediyne followed the expected cycloaddition with the alkene in the neighbouring arm to form a stable bridged bicyclic enediyne. 相似文献
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Electrochemical capacitors, based on the double-layer capacitance of high specific surface area carbon materials, are attracting major fundamental and technological interest as highly reversible, electrical-charge storage and delivery devices, capable of being operated at high power densities. In the present paper, studies have been carried out on nanocomposite gel polymer electrolyte comprising poly(vinylidene fluoride-co-hexafluoropropylene)-propylene carbonate-magnesium perchlorate-nanofumed silica with a view to use them as electrolyte in electrochemical double-layer capacitors (EDLCs) based on chemically treated activated charcoal as electrodes. The optimized composition of nanogel polymer electrolyte exhibits high room-temperature ionic conductivity of 5.4?×?10?3 S cm?1 with good mechanical and dimensional stability which is suitable for their application as electrolyte in EDLCs. Detailed chemical and microstructural characterization of chemically treated and untreated activated charcoal was conducted using scanning electron microscopy and Brunauer–Emmett–Teller (BET). BET studies reveal that the effective surface area of treated activated charcoal powder (1,515 m2 g?1) increases by more than double-fold compared with untreated one (721 m2 g?1). Performance characteristics of EDLCs have been tested using cyclic voltammetry, impedance spectroscopy, prolonged cyclic test, and charge–discharge techniques. Analysis shows that the treated activated charcoal electrodes have almost five times more capacitance values as compared with the untreated one. The maximum capacitance of 324 mF cm?2, equivalent to single electrode specific capacitance of 216 F?g?1 was achieved. It corresponds to an energy density of 20 Wh kg?1 and a power density of 2.2 kW kg?1. 相似文献