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排序方式: 共有147条查询结果,搜索用时 15 毫秒
1.
Modified Stern-Volmer equation is obeyed by bovine serum albumin (BSA)-iodide system showing selective quenching of tryptophanyl
fluorescence of BSA. The fraction of accessible protein fluorescence is 0.56 and the effective Stern-Volmer constant is 290
M-1 at pH 7.4 in 0.005 M phosphate buffer at 25°C. Collisional quenching is operative both in the BSA -I−1 system and the model system, tryptophan-I−1. It is supported by the observed relationship between the ratio of quenching rate constants (k
q
) and diffusion coefficients and alsok
q
with bulk viscosity. 相似文献
2.
G.?V.?Ramana.?ReddyEmail author S.?Selvakumar L.?J.?Francisca 《Colloid and polymer science》2005,283(10):1085-1090
Kinetic study of aqueous polymerization of ethyl acrylate (EA) is carried out at 30 °C in dilute sulphuric acid medium by employing ammonium ceric sulphate–methyl ethyl ketone (MEK) as redox initiator system. The ceric ion consumption is found to be first order with respect to ceric ion and half order with respect to reducing agent concentrations. No complex formation between ceric ion and reducing agent is observed. The orders with respect to ceric ion, reducing agent and monomer concentrations are evaluated for the aqueous polymerization of EA by Ce(IV)–MEK redox initiator system, and are found to be 0.5, 0.5 and 1.4, respectively . The overall activation energy, E
overall, for aqueous polymerization of EA in the temperature region of 27–40°C is found to be 20.27 kJ/mol. A kinetic scheme for the aqueous polymerization of EA initiated by Ce(IV)–MEK redox initiator system is presented.This revised version was published online in June 2005 with corrections to figure legends as well as small corrections within text. 相似文献
3.
Thangavelu Saravanan Rajendran Selvakumar Mukesh Doble Anju Chadha 《Tetrahedron: Asymmetry》2012,23(18-19):1360-1368
The stereochemical preference of the biocatalyst, Candida parapsilosis ATCC 7330, was investigated with respect to the E/Z configuration in the deracemization and the asymmetric reduction of aryl secondary alcohols and prochiral ketones, respectively. The biocatalyst preferred the E-isomers over Z-isomers as substrates as evidenced from the experimental results of >99% ee and up to 86% isolated yield for E-secondary alcohols. The synthesis of enantiomerically pure E-4-phenylbut-3-ene-1,2-diol (ee >99%, isolated yield 86%) by whole cell mediated deracemization is reported here for the first time. The geometric preference of the enzymes was confirmed by using the cell free extract of this biocatalyst. Mechanistic insights using in silico studies showed that the E-isomers when located in the active site are favourably placed with respect to the catalytic triad (Ser-Tyr-Lys) for hydride transfer from NADPH. 相似文献
4.
Herein, synthesis of a series of naphtho[2,3-f]quinolin-13-one and naphtho[2,3-a]acridin-1(2H)-one derivatives directly by one-pot multi-component reaction of 1,3-dicarbonyl compounds (1,3-indanedione/1,3-cyclohexanedione), 2-aminoantharacene/2-naphthylamine and various substituted aldehydes under solvent-free conditions using heteropoly-11-molybdo-1-vanadophosphoric acid supported on montmorillonite K-10 clay catalyst (10% PVMoK-10) is reported. The successful formation of naphtho[2,3-f]quinolin-13-one and naphtho[2,3-a]acridin-1(2H)-one derivatives was confirmed by various spectroscopic techniques. This study offers a green approach for the synthesis of novel quinolinone derivatives. 相似文献
5.
Metal‐Free CH Bond Activation of Branched Aldehydes with a Hypervalent Iodine(III) Catalyst under Visible‐Light Photolysis: Successful Trapping with Electron‐Deficient Olefins
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Dr. Shin A. Moteki Asuka Usui Dr. Sermadurai Selvakumar Dr. Tiexin Zhang Prof. Dr. Keiji Maruoka 《Angewandte Chemie (International ed. in English)》2014,53(41):11060-11064
Direct acyl radical formation of linear aldehydes (RCH2‐CHO) and subsequent hydroacylation with electron‐deficient olefins can be effected with various types of metal and nonmetal catalysts/reagents. In marked contrast, however, no successful reports on the use of branched aldehydes have been made thus far because of their strong tendency of generating alkyl radicals through the facile decarbonylation of acyl radicals. Here, use of a hypervalent iodine(III) catalyst under visible light photolysis allows a mild way of generating acyl radicals from various branched aldehydes, thereby giving the corresponding hydroacylated products almost exclusively. Another characteristic feature of this approach is the catalytic use of hypervalent iodine(III) reagent, which is a rare example on the generation of radicals in hypervalent iodine chemistry. 相似文献
6.
Sridevi Duggirala Rakesh P. Nankar Selvakumar Rajendran Mukesh Doble 《Applied biochemistry and biotechnology》2014,174(1):283-296
Naturally occurring phytochemicals with reported antibacterial activity were screened for their ability to inhibit the bacterial cell division protein Escherichia coli FtsZ. Among the representative compounds, coumarins inhibit the GTPase and polymerization activities of this protein effectively. Further screening with ten coumarin analogs we identified two promising candidates, scopoletin and daphnetin. The former is found to inhibit the GTPase activity of the protein in a noncompetitive manner. Docking of these coumarins with the modeled protein indicate that they bind to T7 loop, which is different from the GTP-binding site (active site), thereby supporting the experimental data. Lowest binding energy is obtained with scopoletin. 3D QSAR indicates the need for groups such as hydroxyl, diethyl, or dimethyl amino in the 7th carbon for enhanced activity. None of the coumarins exhibited cytotoxicity against NIH/3T3 and human embryonic kidney cell lines. The length of Bacillus subtilis increases in the presence of these compounds probably due to the lack of septum formation. Results of this study indicate the role of coumarins in halting the first step of bacterial cell division process. 相似文献
7.
One-pot multi-component synthesis of N,N′-alkylidene bisamides, 2,4,5-trisubstituted imidazoles and 1,2,4,5-tetrasubstituted imidazoles in the presence of catalytic material heteropoly-11-tungsto-1-vanadophosphoric acid (HPV) supported on activated natural clay for about 20% (HPVAC-20) under solvent-free reaction condition have been achieved. Green heterogeneous reaction condition, simple workup procedure, short reaction time, high yield of products, and reusability of the catalyst are the advantages of this protocol. 相似文献
8.
The chemical bonding, electronic structure, and optical properties of metal-organic framework-5 (MOF-5) were systematically investigated using ab initio density functional calculations. The unit cell volume and atomic positions were optimized with the Perdew-Burke-Ernzerhof (PBE) functional leading to a good agreement between the experimental and the theoretical equilibrium structural parameters. The calculated bulk modulus indicates that MOF-5 is a soft material. The estimated band gap from a density of state (DOS) calculation for MOF-5 is about 3.4 eV, indicating a nonmetallic character. As MOFs are considered as potential materials for photocatalysts, active components in hybrid solar cells, and electroluminescence cells, the optical properties of this material were investigated. The detailed analysis of chemical bonding in MOF-5 reveals the nature of the Zn-O, O-C, H-C, and C-C bonds, that is, Zn-O having mainly ionic interaction whereas O-C, H-C, and C-C exhibit mainly covalent interactions. The findings in this paper may contribute to a comprehensive understanding about this kind of material and shed insight into the synthesis and application of novel and stable MOFs. 相似文献
9.
Recent developments in microbial inulinases 总被引:15,自引:0,他引:15
Ashok Pandey Carlos R. Soccol Ponniah Selvakumar Vanete T. Soccol Nadia Krieger Jose D. Fontana 《Applied biochemistry and biotechnology》1999,81(1):35-52
Microbial inulinases are an important class of industrial enzymes that have gained much attention recently. Inulinases can
be produced by a host of microorganisms, including fungi, yeast, and bacteria. Among them, however, Aspergillus sp. (filamentous fungus) and Kluyveromyces sp. (diploid yeast) are apparently the preferred choices for commercial applications. Among various substrates (carbon source)
employed for their production, inulin-containing plant materials offer advantages in comparison to pure substrates. Although
submerged fermentation has been universally used as the technique of fermentation, attempts are being made to develop solidstate
fermentation technology also. Inulinases catalyze the hydrolysis of inulin to d-fructose (fructose syrup), which has gained an important place in human diets today. In addition, inulinases are finding
other newer applications. This article reviews more recent developments, especially those made in the past decade, on microbial
inulinases—its production using various microorganisms and substrates. It also describes the characteristics of various forms
of inulinases produced as well as their applications. 相似文献
10.
J. Selvakumar V. S. Raghunathan K. S. Nagaraja 《Journal of Thermal Analysis and Calorimetry》2010,100(1):155-161
The volatile scandium-β-diketonates are synthesised using acetylacetone (acac) and tetramethylheptanedione (tmhd) as coordinative
ligands for CVD application. The X-ray powder patterns are indexed and analysed and found to be orthorhombic and monoclinic
phases for Sc(acac)3(1) and Sc(tmhd)3(2) respectively. The sublimation and evaporation kinetics have been analyzed using three calculating techniques. The non-isothermal
based activation energy values are found to be 38 ± 2 and 73 ± 2 kJ mol−1 by Flynn–Wall technique for (1) and (2) respectively. The measured Ea values are close to the value obtained using Kissinger method. 相似文献