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931.
Biocompatible organic acids and citrate-stabilized gold nanoparticles were interacted with nisin to generate robust antimicrobial agents, which display archetypical nisin activity even at elevated pH. 相似文献
932.
An organocatalytic construction of optically enriched substituted pyran derivatives via amine-catalyzed Michael addition and subsequent enolization/cyclisation has been described starting from electronically poor alkenes. Functionalized pyrans were obtained in high enantioselectivities (up to 96%) and good yields (up to 90%) having three contiguous chiral centers. 相似文献
933.
Subhajit Saha Bhaskar Das Nilesh Mazumder Anurag Bharati Kalyan Kumar Chattopadhyay 《Journal of Sol-Gel Science and Technology》2012,61(3):518-526
Magnesium aluminate nanoparticles with different chromium concentration (0–12%) have been synthesized by a citrate–nitrate
sol–gel route. X-ray diffraction studies confirmed the formation of single-phase cubic spinel structure excluding the presence
of any secondary phase. Crystallite size of the synthesized nanoparticles was found to increase from 8.5 to 19.8 nm with the
increase in Cr concentration. Fourier transformed infrared spectroscopic studies confirmed the presence of AlO6 group which led to the formation of MgAl2O4 spinel structure. Surface morphology of the sintered pellets was investigated with the help of a field emission scanning
electron microscope which revealed the existence of both grain and grain boundary along with their aggregates. The dielectric
constant, dielectric loss and ac conductivity were studied as a function of frequency of the applied electric field for different
composition and their nature of variation with frequency has been elucidated on the basis of Maxwell–Wagner interfacial model.
Impedance spectroscopy technique has been used to study the effect of grain and grain boundary on the electrical properties
of this spinel oxide. All the electrical parameters showed strong dependence on the nanostructural properties and were found
to vary consistently with the increase of doping concentration. 相似文献
934.
Subhabrata Maiti Krishnendu Das Sounak Dutta Prof. Prasanta Kumar Das 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(47):15021-15030
This work demonstrates a remarkable enhancement in the peroxidase activity of mitochondrial membrane protein cytochrome c (cyt c) by perturbing its tertiary structure in the presence of surface‐functionalised gold nanoparticles (GNPs) within cetyltrimethylammonium bromide (CTAB) reverse micelles. The loss in the tertiary structure of cyt c exposes its heme moiety (which is buried inside in the native globular form), which provides greater substrate (pyrogallol and H2O2) accessibility to the reactive heme residue. The surfactant shell of the CTAB reverse micelle in the presence of co‐surfactant (n‐hexanol) exerted higher crowding effects on the interfacially bound cyt c than similar anionic systems. The congested interface led to protein unfolding, which resulted in a 56‐fold higher peroxidase activity of cyt c than that in water. Further perturbation in the protein’s structure was achieved by doping amphiphile‐capped GNPs with varying hydrophobicities in the water pool of the reverse micelles. The hydrophobic moiety on the surface of the GNPs was directed towards the interfacial region, which induced major steric strain at the interface. Consequently, interaction of the protein with the hydrophobic domain of the amphiphile further disrupted its tertiary structure, which led to better opening up of the heme residue and, thereby, superior activity of the cyt c. The cyt c activity in the reverse micelles proportionately enhanced with an increase in the hydrophobicity of the GNP‐capping amphiphiles. A rigid cholesterol moiety as the hydrophobic end group of the GNP strikingly improved the cyt c activity by up to 200‐fold relative to that found in aqueous buffer. Fluorescence studies with both a tryptophan residue (Trp59) of the native protein and the sodium salt of fluorescein delineated the crucial role of the hydrophobicity of the GNP‐capping amphiphiles in improving the peroxidase activity of cyt c by unfolding its tertiary structure within the reverse micelles. 相似文献
935.
Priyadip Das Amal Kumar Mandal Nellore Bhanu Chandar Mithu Baidya Harshad B. Bhatt Bishwajit Ganguly Dr. Sudip K. Ghosh Dr. Amitava Das 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(48):15382-15393
In this work, we have rationally designed and synthesized two new reagents ( L1 and L2 ), each bearing a pendant aldehyde functionality. This aldehyde group can take part in cyclization reactions with β‐ or γ‐amino thiols to yield the corresponding thiazolidine and thiazinane derivatives, respectively. The intramolecular charge‐transfer (ICT) bands of these thiazolidine and thiazinane derivatives are distinctly different from those of the molecular probes ( L1 and L2 ). Such changes could serve as a potential platform for using L1 and L2 as new colorimetric/fluorogenic as well as ratiometric sensors for cysteine (Cys) and homocysteine (Hcy) under physiological conditions. Both reagents proved to be specific towards Cys and Hcy even in the presence of various amino acids, glucose, and DNA. Importantly, these two chemodosimetric reagents could be used for the quantitative detection of Cys present in blood plasma by using a pre‐column HPLC technique. Such examples are not common in contemporary literature. MTT assay studies have revealed that these probes have low cytotoxicity. Confocal laser scanning micrographs of cells demonstrated that these probes could penetrate cell membranes and could be used to detect intracellular Cys/Hcy present within living cells. Thus, the results presented in this article not only demonstrate the efficiency and specificity of two ratiometric chemodosimeter molecules for the quantitative detection of Cys and Hcy, but also provide a strategy for developing reagents for analysis of these vital amino acids in biological samples. 相似文献
936.
937.
A simple, straightforward, and highly efficient diastereoselective multicomponent one-pot synthesis of a series of pharmaceutically interesting functionalized piperidine derivatives has been developed based on a low-cost and environmentally benign Bi(NO3)3·5H2O catalyst via tandem reactions of 1,3-dicarbonyl compounds, aromatic aldehydes, and various amines in ethanol at room temperature. High atom-economy, good yields, eco-friendliness, and mild reaction conditions are some of the important features of this protocol. 相似文献
938.
Dharminder Sharma Sandeep Kumar Arun K. Shil Nitul Ranjan Guha Pralay Das 《Tetrahedron letters》2012,53(52):7044-7051
Solid supported palladium nano/microparticles were found to be active catalysts to perform mono- and β,β-double-Heck reactions. Different β-unsubstituted and substituted alkenes including acrylate, methacrylate, crotonate, styrene, acrylonitrile, and acrylamide were investigated successfully for mono- and β,β-double-Heck reactions with aryl iodide under milder reaction condition. One-pot β,β-double-Heck reaction of aryl iodides with α,β-unsaturated ester, amide, nitrile, and styrene derivatives were also performed under standard reaction conditions. Wide functional group tolerance, easy catalyst recovery, and recyclability up to twelve times without significant loss of catalytic activity added extra importance to the present process. 相似文献
939.
The solvent relaxation and rotational dynamics of coumarin 153 have been investigated in a new room temperature ionic liquid, 1-(2-methoxyethyl)-1-methylpyrrolidiniumtris(pentafluorethyl)trifluorophosphate [[MOEMPL][FAP]], at three different excitation wavelengths with a variation in temperature. Wavelength -dependent fluorescence decay behavior of the probe molecule in the present medium has been investigated by studying the time dependent fluorescence Stokes shift in the ps–ns time scale. The dynamic fluorescence Stokes shift measurements suggest that the time-resolvable part of the solvation dynamics is biphasic in nature and the average solvation time depends on the excitation wavelengths. Rotational coupling constants, obtained from the time- resolved anisotropy data, indicate no specific interaction between the probe molecule and the ionic liquids. The excitation wavelength dependent solvation dynamics is attributed to the heterogeneous nature of the present ionic liquid. 相似文献
940.
J. Tripathi J.M. Keller K. Das S. Tripathi T. Shripathi 《Journal of Physics and Chemistry of Solids》2012,73(8):1026-1033
Contribution of Rhodamine B doping on the structural and optical properties of PVA is investigated here. With increasing doping wt%, Raman spectra show the disappearance of main PVA peaks revealing a decrease in crystallinity and breaking of bonds, which also results in modified surface morphology as seen from corresponding SEM measurements. Optical absorption measurements show the possibility of both direct and indirect transitions, also indicating strong modifications in optical properties as a result of doping fluorescent dye in the polymer host. 相似文献