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Fast Proton Exchange in Histidine: Measurement of Rate Constants through Indirect Detection by NMR Spectroscopy 下载免费PDF全文
Akansha Ashvani Sehgal Dr. Luminita Duma Prof. Geoffrey Bodenhausen Dr. Philippe Pelupessy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6332-6338
Owing to its imidazole side chain, histidine participates in various processes such as enzyme catalysis, pH regulation, metal binding, and phosphorylation. The determination of exchange rates of labile protons for such a system is important for understanding its functions. However, these rates are too fast to be measured directly in an aqueous solution by using NMR spectroscopy. We have obtained the exchange rates of the NH3+ amino protons and the labile NHε2 and NHδ1 protons of the imidazole ring by indirect detection through nitrogen‐15 as a function of temperature (272 K<T<293 K) and pH (1.3<pH<4.9) of uniformly nitrogen‐15‐ and carbon‐13‐labeled L ‐histidine ? HCl ? H2O. Exchange rates up to 8.5×104 s?1 could be determined (i.e., lifetimes as short as 12 μs). The three chemical shifts δHi of the invisible exchanging protons Hi and the three one‐bond scalar coupling constants 1J(N,Hi) could also be determined accurately. 相似文献
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Bimetallic Ag‐Pt Sub‐nanometer Supported Clusters as Highly Efficient and Robust Oxidation Catalysts 下载免费PDF全文
Dr. Fabio R. Negreiros Dr. Avik Halder Dr. Chunrong Yin Dr. Akansha Singh Dr. Giovanni Barcaro Dr. Luca Sementa Dr. Eric C. Tyo Dr. Michael J. Pellin Dr. Stephan Bartling Dr. Karl‐Heinz Meiwes‐Broer Dr. Sönke Seifert Dr. Prasenjit Sen Dr. Sandeep Nigam Dr. Chiranjib Majumder Dr. Nobuyuki Fukui Dr. Hisato Yasumatsu Dr. Stefan Vajda Dr. Alessandro Fortunelli 《Angewandte Chemie (International ed. in English)》2018,57(5):1209-1213
A combined experimental and theoretical investigation of Ag‐Pt sub‐nanometer clusters as heterogeneous catalysts in the CO→CO2 reaction (COox) is presented. Ag9Pt2 and Ag9Pt3 clusters are size‐selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and by first‐principles simulations at realistic coverage. In situ GISAXS/TPRx demonstrates that the clusters do not sinter or deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano‐aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O2, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species. 相似文献
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Deshmukh Amarsinh R. Bhosle Manisha R. Khillare Lalit D. Dhumal Sambhaji T. Mishra Akansha Srivastava Arvind K. Mane Ramrao A. 《Research on Chemical Intermediates》2017,43(2):1107-1120
Research on Chemical Intermediates - We report synthesis and in vivo antihyperglycemic evaluation of new 3-substituted... 相似文献
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Monalisa Mishra Debabrat Sabat Basanti Ekka Swetapadma Sahu Unnikannan P Priyabrat Dash 《Journal of nanoparticle research》2017,19(8):282
Zirconia nanoparticles (ZrO2 NPs) have been extensively used in teeth and bone implants and thus get a chance to interact with the physiological system. The current study investigated the oral administration of various concentrations of ZrO2 NPs synthesized by the hydrothermal method (0.25 to 5.0 mg L?1) on Drosophila physiology and behaviour. The size of the currently studied nanoparticle varies from 10 to 12 nm. ZrO2 NPs accumulated within the gut in a concentration-dependent manner and generate reactive oxygen species (ROS) only at 2.5 and 5.0 mg L?1 concentrations. ROS was detected by nitroblue tetrazolium (NBT) assay and 2′,7′-dichlorofluorescein (H2DCF) staining. The ROS toxicity alters the larval gut structure as revealed by DAPI staining. The NP stress of larvae affects the Drosophila development by distressing pupa count and varying the phenotypic changes in sensory organs (eye, thorax bristle, wings). Besides phenotypic changes, flawed climbing behaviour against gravity was seen in ZrO2 NP-treated flies. All together, for the first time, we have reported that a ROS-mediated ZrO2 NP toxicity alters neuronal development and functioning using Drosophila as a model organism. 相似文献
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Ravi Kumar Thakur Akansha Mishra K.K.G. Ramakrishna Rohit Mahar Sanjeev K. Shukla A.K. Srivastava Rama P. Tripathi 《Tetrahedron》2014
A series of novel nucleoside analogues having dual bases (pyrimidine and triazole) and sugars have been synthesized by CuAAC reaction of azido sugars with propynylated pyrimidines. These compounds were evaluated for their in vitro α-glucosidase inhibitory activity. In this series, compounds 4b, 4d, 8a, 8b, 8c, 8e, 8g, 8h, and 8i exhibited very good inhibition of α-glucosidase enzyme. Nucleoside analogues 8a, 4b, 8h, and 8c displayed 47.4%, 41.8%, 39.4%, and 34.6% inhibition, respectively, comparable to the standard drug acarbose (53.4%). 相似文献
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Physicochemical properties such as density (ρ), viscosity (η), ultrasonic speed (u) of ionic liquid tetrabutylphosphonium tetrafluoroborate in acetonitrile, tetrahydrofuran, 1,3-dioxolane, and their binaries have been studied over the entire range of composition at 298.15°K. Apparent molar volumes (? V ) and viscosity B-coefficients supplemented with the data of densities and viscosities, respectively, have been interpreted in terms of ion–solvent interactions. The limiting apparent molar volumes (? V 0 ), experimental slopes (S V ? ) derived from the Masson equation, and viscosity A and B-coefficients analyzed by the Jones–Dole equation have also been interpreted. The adiabatic compressibility (β) has been evaluated using the ultrasonic speed (u) values. Thereafter, limiting apparent molar adiabatic compressibilities (? K 0 ) have been evaluated and discussed for the same. Figure
Novelty and main finding: The derived communications of an ionic liquid widespreading in significant solvents enable the researchers to focus on replacing VOSs by proper solvents for simple transformations with minimum chemical waste and environmental pollution. 相似文献
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S. Aurosman Pappus Basanti Ekka Swetapadma Sahu Debabrat Sabat Priyabrat Dash Monalisa Mishra 《Journal of nanoparticle research》2017,19(4):136
The effects of oral intake of hydroxyapatite nanoparticles (HApNPs) were investigated on growth, development and behaviour of Drosophila. The Drosophila responses to various concentrations of HApNPs were compared. At lower concentrations, i.e. 5 mg L?1 more amount of oxidative stress was produced than that of highest concentration, i.e. 80 mg L?1. The increased amounts of oxidative stress reflect a higher amount of ROS production and increased cell damage within the larval gut. HApNPs was further shown to interfere with the calcium and phosphorus absorption pathway. Besides all these damage, HApNPs causes developmental delay in the late third instar larvae. The most significant anomaly was observed in pupae count, fly hatching after the feeding of HApNPs. Flies hatched from treated vials have decreased body weight with defective walking behaviour. Hatched flies have a phenotypic defect in the wing, eye and thorax of the bristles. Along with these changes, the adult fly becomes more prone towards stress. The findings hint that HApNPs persuade noxious effects and alter the development, structure, function and behaviour of the fly in a concentration-dependent manner. 相似文献
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Dr. Samim Khan Dr. Akhtaruzzaman Dr. Raghavender Medishetty Akansha Ekka Dr. Mohammad Hedayetullah Mir 《化学:亚洲杂志》2021,16(19):2806-2816
Some special crystals respond to light by jumping, scattering or bursting just like popping of popcorn kernels on a hot surface. This rare phenomenon is called the photosalient (PS) effect. Molecular level control over the arrangement of light-responsive molecules in microscopic crystals for macroscale deformation or mechanical motion offers the possibility of using light to control smart material structures across the length scales. Photochemical [2+2] cycloaddition has recently emerged as a promising route to obtain photoswitchable structures and a wide variety of frameworks, but such reaction in crystals leading to macroscopic mechanical motion is relatively less explored. Study of chemistry of such novel soft crystals for the generation of smart materials is an imperative task. This minireview highlights recent advances in solid-state [2+2] cycloaddition in crystals to induce macroscale mechanical motion and thereby transduction of light into kinetic energy. 相似文献
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Arora Akansha Ram Samrith Venkateswarlu Ayineedi 《Journal of Algebraic Combinatorics》2021,53(4):1299-1312
Journal of Algebraic Combinatorics - We consider some combinatorial problems on matrix polynomials over finite fields. Using results from control theory, we give a proof of a result of Lieb, Jordan... 相似文献