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21.
Tushar K. Chakraborty B.Krishna MohanS.Kiran Kumar Ajit C. Kunwar 《Tetrahedron letters》2003,44(3):471-473
Synthesis and conformational studies of two short peptides containing pyrrole amino acids (1, Paa), Boc-Paa-Paa-d-Pro-Gly-Xaa-Paa-Paa-OMe (2: Xaa=Ala; 3: Xaa=Val), were carried out in which it was established that replacement of Ala in 2 with a Val residue helps peptide 3 to adopt a well-defined β-hairpin conformation in a nonpolar solvent, like CDCl3. 相似文献
22.
Dr. Sunil Varughese Dr. Mangalampalli S. R. N. Kiran Prof. Upadrasta Ramamurty Prof. Gautam R. Desiraju 《化学:亚洲杂志》2012,7(9):2118-2125
Nanoindentation and scratch experiments on 1:1 donor–acceptor complexes, 1 and 2 , of 1,2,4,5‐tetracyanobenzene with pyrene and phenanthrene, respectively, reveal long‐range molecular layer gliding and large interaction anisotropy. Due to the layered arrangements in these crystals, these experiments that apply stress in particular directions result in the breaking of interlayer interactions, thus allowing molecular sheets to glide over one another with ease. Complex 1 has a layered crystal packing wherein the layers are 68° skew under the (002) face and the interlayer space is stabilized by van der Waals interactions. Upon indenting this surface with a Berkovich tip, pile‐up of material was observed on just one side of the indenter due to the close angular alignment of the layers with the half angle of the indenter tip (65.35°). The interfacial differences in the elastic modulus (21 %) and hardness (16 %) demonstrate the anisotropic nature of crystal packing. In 2 , the molecular stacks are arranged in a staggered manner; there is no layer arrangement, and the interlayer stabilization involves C? H???N hydrogen bonds and π???π interactions. This results in a higher modulus (20 %) for (020) as compared to (001), although the anisotropy in hardness is minimal (4 %). The anisotropy within a face was analyzed using AFM image scans and the coefficient of friction of four orthogonal nanoscratches on the cleavage planes of 1 and 2 . A higher friction coefficient was obtained for 2 as compared to 1 even in the cleavage direction due to the presence of hydrogen bonds in the interlayer region making the tip movement more hindered. 相似文献
23.
Rane Vipul P. Patil Rushikesh H. Patil Kiran R. Pathan Amin R. Naik Sukantakumar Ahirrao Vinod K. Jadhav Rajiv A. Yeole Ravindra D. 《Chromatographia》2022,85(2):155-165
Chromatographia - WCK 771 is a novel antibacterial drug recently launched in India for the treatment of acute bacterial skin and skin structure infections (ABSSSI). This report describes... 相似文献
24.
Harsha K. Tripathy S. V. Nair Manju Rama Murthy Bestha Vinay Kiran Sreekanth Dittakavi Ramesh Mullangi 《Biomedical chromatography : BMC》2022,36(8):e5387
In this study, we report the development and validation of an LC–tandem mass spectrometry method for the simultaneous quantitation of bendamustine and copanlisib in mouse plasma as per the US FDA regulatory guidelines. The sample processing involves extraction of bendamustine and copanlisib along with internal standard (IS; warfarin) from 50 μL mouse plasma using a liquid–liquid extraction method. The chromatographic separation of bendamustine, copanlisib and the IS was achieved on an Atlantis dC18 column using an isocratic mobile phase (5 mM ammonium acetate:methanol, 20:80 v/v). Bendamustine, copanlisib and the IS eluted at 0.88, 1.39 and 0.74 min, respectively, with a total run time of 2.5 min. The calibration curve ranged from 3.99–2996 and 4.33–3248 ng/mL for bendamustine and copanlisib, respectively. Inter- and intra-day precision and accuracy, stability in processed samples and upon storage, dilution integrity and incurred sample reanalysis were investigated for both the analytes. The intra- and inter-day precisions were in the ranges of 2.01%–5.05% and 2.74%–6.13% and 1.98%–7.64 and 8.62%–9.04% for bendamustine and copanlisib, respectively. Stability studies showed that both analytes were stable on bench top for 6 h, in auto-sampler for 24 and at −80°C for 30 days. The validated method was successfully applied to a pharmacokinetic study in mice. 相似文献
25.
Journal of Thermal Analysis and Calorimetry - Carbon-based nano- and microfluid dispersions show promise as effective media for solar-assisted desalination. They act as strong solar absorbers in... 相似文献
26.
Detailed gas-phase chemical kinetic models are widely used in combustion research, and many new mechanisms for different fuels and reacting conditions are developed each year. Recent works have highlighted the need for error checking when preparing such models, but a useful community tool to perform such analysis is missing. In this work, we present a simple online tool to screen chemical kinetic mechanisms for bimolecular reactions exceeding collision limits. The tool is implemented on a user-friendly website, cloudflame.kaust.edu.sa, and checks three different classes of bimolecular reactions; (ie, pressure independent, pressure-dependent falloff, and pressure-dependent PLOG). In addition, two other online modules are provided to check thermodynamic properties and transport parameters to help kinetic model developers determine the sources of errors for reactions that are not collision limit compliant. Furthermore, issues related to unphysically fast timescales can remain an issue even if all bimolecular reactions are within collision limits. Therefore, we also present a procedure to screen ultrafast reaction timescales using computational singular perturbation. For demonstration purposes only, three versions of the rigorously developed AramcoMech are screened for collision limit compliance and ultrafast timescales, and recommendations are made for improving the models. Larger models for biodiesel surrogates, tetrahydropyran, and gasoline surrogates are also analyzed for exemplary purposes. Numerical simulations with updated kinetic parameters are presented to show improvements in wall-clock time when resolving ultrafast timescales. 相似文献
27.
Yae Eun Chong Manting Chiang Kiran Deshpande Simon Haroutounian Leonid Kagan Jong Bong Lee 《Biomedical chromatography : BMC》2019,33(11)
Ondansetron, a widely used antiemetic agent, is a P‐glycoprotein (P‐gp) substrate and therefore expression of P‐gp at the blood–brain barrier limits its distribution to the central nervous system (CNS), which was observed to be reversed by coadministration with P‐gp inhibitors. Tariquidar is a potent and selective third‐generation P‐gp inhibitor, and coadministration with ondansetron has shown improved ondansetron distribution to the CNS. There is currently no reported bioanalytical method for simultaneously quantifying ondansetron with a third‐generation P‐gp inhibitor. Therefore, we aimed to develop and validate a method for ondansetron and tariquidar in rat and human plasma samples. A full validation was performed for both ondansetron and tariquidar, and sample stability was tested under various storage conditions. To demonstrate its utility, the method was applied to a preclinical pharmacokinetic study following coadministration of ondansetron and tariquidar in rats. The presented method will be valuable in pharmacokinetic studies of ondansetron and tariquidar in which simultaneous determination may be required. In addition, this is the first report of a bioanalytical method validated for quantification of tariquidar in plasma samples. 相似文献
28.
Subhrakant Jena Kiran Devi Tulsiyan Dr. Rajiv K. Kar Dr. Hemanta K. Kisan Dr. Himansu S. Biswal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(13):4373-4383
Designing a potential protein–ligand pair is pivotal, not only to track the protein structure dynamics, but also to assist in an atomistic understanding of drug delivery. Herein, the potential of a small model thioamide probe being used to study albumin proteins is reported. By monitoring the Förster resonance energy transfer (FRET) dynamics with the help of fluorescence spectroscopic techniques, a twofold enhancement in the FRET efficiency of 2-thiopyridone (2TPY), relative to that of its amide analogue, is observed. Molecular dynamics simulations depict the relative position of the free energy minimum to be quite stable in the case of 2TPY through noncovalent interactions with sulfur, which help to enhance the FRET efficiency. Finally, its application is shown by pairing thiouracils with protein. It is found that the site-selective sulfur atom substitution approach and noncovalent interactions with sulfur can substantially enhance the FRET efficiency, which could be a potential avenue to explore in the design of FRET probes to study the structure and dynamics of biomolecules. 相似文献
29.
Kiran Singhal Dharmendra K. Srivastava 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1673-1678
Abstract Interactions of HgX2 (X = Cl, Br, I, SCN, CN, NCO), SbCl3, TeCl4, and PhTeCl3 with Ph3Sn-O-SiPh3 at room temperature have been found to proceed with the simultaneous cleavage of Sn-O and Si-O bonds, invariably yielding Ph2SnO, Ph3SiX, and the corresponding organo-mercury, -antimony, and -tellurium derivatives. The course of the reactions suggests the instability of the Sn-O-M (M = Hg, Sb, Te) system. GRAPHICAL ABSTRACT 相似文献
30.
In order to establish a rapid conversion method of primary amides to nitriles, various types of carboxamides were treated with 2,2,2-trichloroethyl chloroformate and Et3N, as a dehydrating agent to obtain the desired nitriles in 82–95% yields. 相似文献