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931.
932.
Sushmita Dr. Trapti Aggarwal Prof. Norio Shibata Prof. Akhilesh K. Verma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16063-16067
A metal-free, versatile triple-bond directed approach for the decarbonylative C−H amination of ortho-alkynyl quinoline/pyridine aldehydes using N-fluorobenzenesulfonimide as nitrogen source under mild reaction conditions has been described. The designed reaction strategy was triggered by trapping of fluorine by base with subsequent attack of bis(phenylsulfonyl)-λ2-azane on the carbonyl carbon of a heterocycle, which was gradually converted into the corresponding amine through a Curtius type rearrangement. This protocol provides a one-step approach for the conversion of aldehydes into amines in good yields. The synthesized amines were successfully transformed into biologically important pyrroloquinolines/pyridines. 相似文献
933.
Tripathi Alok Kumar Verma Yogendra Lal Shalu Singh Varun Kumar Balo Liton Gupta Himani Singh Shishir Kumar Singh Rajendra Kumar 《Journal of Solid State Electrochemistry》2017,21(11):3365-3371
Journal of Solid State Electrochemistry - Quasi solid-state electrolytes (QS-SEs) based on an ionic liquid ([EMIM][FSI]) immobilized in ordered mesoporous silica MCM-41 using physical imbibition... 相似文献
934.
Sandeep Verma Prasenjit Kar Amitava Das Dr. Dipak K. Palit Dr. Hirendra N. Ghosh Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(2):611-619
We have synthesized ruthenium(II)– and osmium(II)–polypyridyl complexes ([M(bpy)2 L ]2+, in which M=OsII or RuII, bpy=2,2′‐bipyridyl, and L =4‐(2,2′‐bipyridinyl‐4‐yl)benzene‐1,2‐diol) and studied the interfacial electron‐transfer process on a TiO2 nanoparticle surface using femtosecond transient‐absorption spectroscopy. Ruthenium(II)‐ and osmium(II)‐based dyes have a similar molecular structure; nevertheless, we have observed quite different interfacial electron‐transfer dynamics (both forward and backward). In the case of the RuII/TiO2 system, single‐exponential electron injection takes place from photoexcited nonthermalized metal‐to‐ligand charge transfer (MLCT) states. However, in the case of the OsII/TiO2 system, electron injection takes place biexponentially from both nonthermalized and thermalized MLCT states (mainly 3MLCT states). Larger spin–orbit coupling for the heavier transition‐metal osmium, relative to that of ruthenium, accounts for the more efficient population of the 3MLCT states in the OsII‐based dye during the electron‐injection process that yields biexponential dynamics. Our results tend to suggest that appropriately designed OsII–polypyridyl dye can be a better sensitizer molecule relative to its RuII analogue not only due to much broader absorption in the visible region of the solar‐emission spectrum, but also on account of slower charge recombination. 相似文献
935.
Madathumpady Abubaker Habeeb Muhammed Pramod Kumar Verma Samir Kumar Pal Prof. Archana Retnakumari Manzoor Koyakutty Prof. Shantikumar Nair Prof. Thalappil Pradeep Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10103-10112
The synthesis of a luminescent quantum cluster (QC) of gold with a quantum yield of ~4 % is reported. It was synthesized in gram quantities by the core etching of mercaptosuccinic acid protected gold nanoparticles by bovine serum albumin (BSA), abbreviated as AuQC@BSA. The cluster was characterized and a core of Au38 was assigned tentatively from mass spectrometric analysis. Luminescence of the QC is exploited as a “turn‐off” sensor for Cu2+ ions and a “turn‐on” sensor for glutathione detection. Metal‐enhanced luminescence (MEL) of this QC in the presence of silver nanoparticles is demonstrated and a ninefold maximum enhancement is seen. This is the first report of the observation of MEL from QCs. Folic acid conjugated AuQC@BSA was found to be internalized to a significant extent by oral carcinoma KB cells through folic acid mediated endocytosis. The inherent luminescence of the internalized AuQC@BSA was used in cell imaging. 相似文献
936.
A complete understanding of the relationships between protein structure and stability remains an open problem. Much of our insight comes from laborious experimental analyses that perturb structure via directed mutation. The glycolytic enzyme lysozyme is among the most well characterized proteins under this paradigm, due to its abundance and ease of manipulation. To speed up such analyses, efficient computational models that can accurately predict mutation effects are needed. We employ a minimal Distance Constraint Model (mDCM) to predict the stability of a series of lysozyme mutants (specifically, human wild-type C-type lysozyme and 14 point mutations). With three phenomenological parameters that characterize microscopic interactions, the mDCM parameters are determined by obtaining the least squares error between predicted and experimental heat capacity curves. The mutants are chemically and structurally diverse, but have been experimentally characterized under nearly identical thermodynamic conditions (pH, ionic strength, etc.). The parameters found from best fits to heat capacity curves for one or more lysozyme structures are subsequently used to predict the heat capacity on the remaining. We simulate a typical experimental situation, where prediction of relative stabilities in an untested mutated structure is based on known results as they accumulate. From the statistical significance of these simulations, we establish that the mDCM is a viable predictor for relative stability of protein mutants. Remarkably, using parameters from any single fitting yields an average percent error of 4.3%. Across the dataset, the mDCM reproduces experimental trends sufficiently well (R = 0.64) to be of practical value to experimentalists when making decisions about which mutations to invest time and funds for characterization. 相似文献
937.
Shubhra Ghosh Dastidar Arumugam Madhumalar Gloria Fuentes David P. Lane Chandra S. Verma 《Theoretical chemistry accounts》2010,125(3-6):621-635
The protein MDM2 forms a complex with the tumor suppressing protein p53 and targets it for proteolysis in order to down-regulate p53 in normal cells. Inhibition of this interaction is of therapeutic importance. Molecular dynamics simulations of the association between p53 and MDM2 have revealed mutual modulation of the two surfaces. Analysis of the simulations of the two species approaching each other in solution shows how long range electrostatics steers these two proteins together. The net electrostatics is controlled largely by a few cationic residues that surround the MDM2 binding site. There is an overall separation in electrostatics of MDM2 and p53 that are mutually complementary and drive association. Upon close approach, there is significant energetic strain as the charges are occluded from water (desolvated). However, the complexation is driven by packing interactions that lead to highly favorable van der Waals interactions. Although the complementarity of the electrostatics of the two surfaces is essential for the two partners to form a complex, steric collisions of Y100 and short ranged van der Waals interactions of F19, W23, L26 of p53 determine the final steps of native complex formation. The electrostatics seem to be evolutionarily conserved, including variations in both partners. 相似文献
938.
Thymus linearis (Benth. ex Benth) was collected from five distinct locations of western Himalaya (India) during the summer season. The hydro-distilled essential oil (yield 0.84-0.95%) was analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). A total of 56 constituents, representing 81.55% to 98.11% of the total oil composition, were identified. Thymol (52.28-66.65%), p-cymene (1.81-21.60%) and γ-terpinene (1.94-12.48%) were the major constituents in all populations. Other constituents identified in significant amounts were carvacrol, p-cymen-8-ol, borneol, terpinen-4-ol and thymol methyl ether. The presence of high phenol and essential oil contents in this species make it a suitable substitute for common thyme oil. 相似文献
939.
Molecular-imprinted polymer (MIP) combined with dispersive liquid-liquid micro-extraction (DLLME) were developed for ultra-preconcentration and determination of mononitrotoluenes in wastewater samples using gas chromatography-flame ionization detector. MIP was synthesized by copolymerization of methacrylic acid-ethylene glycole dimethacrylate-2,2-azobisisobutyronitrile as the initiator that imprinted with 3-nitrotoluene as the template molecule. Effects of several factors, such as type and volume of eluent, adsorption, and desorption times of the analyte on the polymer, and breakthrough volume were investigated. Optimization of 3-nitrotoluene extraction from MIP was studied forward followed by DLLME. Preconcentration factor of MIP-DLLME method was about 2800 under the optimum conditions. The LOD of the proposed method was 0.02?μg/L and a linear dynamic range in the range of 0.04-20?μg/L was obtained. The performance of the present method was evaluated for extraction and determination of nitrotoluene compounds in wastewater samples in the range of microgram per liter and satisfactory results were achieved (RSD<13%). 相似文献
940.
The host-guest complex between polyethylene glycol and thiourea dioxide (PEG.TUD) was prepared via different approaches involving co-crystallization method and by a chemical reaction. The resulting PEG.TUD complex was found to be very active and recyclable catalyst for the direct synthesis of 3,4-dihydropyrimidinones via Biginelli condensation and provided high product yields. Interestingly, the corresponding poly(ethylene glycol)-thiourea complexes, PEG.TU, were found to be unreactive and no reaction occurred under similar reaction conditions. 相似文献