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排序方式: 共有394条查询结果,搜索用时 265 毫秒
21.
Yunusa Umar Sahar Abdalla SK Manirul Haque Guillermo Salgado Moran Abdurrahman Ishaq Wilson Cardona Villada Jorge Dagnino Leone Marta Bunster 《中国化学会会志》2020,67(1):62-71
The optimized molecular structures, harmonic vibrational wavenumbers, and the corresponding vibrational assignments of (1S,2S)-tramadol and (1R,2R)-tramadol are computationally examined using the B3LYP density functional theory method together with the standard 6–311++G(d,p) and def2-TVZP basis sets. The optimized structures show that phenolic rings of both 1R,2R and 1S,2S tramadol adopt planar geometry, which are slightly distorted due to the substitution at the meta-position; and the six-membered cyclohexane adopts a slightly distorted chair conformation. The 1S,2S enantiomer is energetically more favorable than 1R,2R with the energy differences of 1.32 and 1.03 kcal/mol obtained at B3LYP/6–311++G(d,p) and B3LYP/Def2-TVZP levels, respectively. The analysis of the binding pocket in the silico molecular docking with the m-opioid receptor shows that it originated two clusters with the 1S,2S enantiomer and one cluster with the 1R,2R enantiomer of tramadol. The results point to a more stable complex of the m-opioid receptor with the 1R,2R enantiomer of tramadol. 相似文献
22.
Tamar Shamai Yamin Hagit Prihed Moran Madmon Merav Blanca Avi Weissberg 《Journal of mass spectrometry : JMS》2020,55(10)
V‐nerve agents present information‐poor spectra, both in GC‐EI‐MS and LC‐ESI‐MS/MS, with dominant fragments/product ions corresponding to the amine‐containing residue. Hence, derivatives/isomers with the same amine residue exhibit similar mass spectral patterns, leading to ambiguity in the phosphonate structure. We present a simple approach for their structural elucidation based on two complementary experiments: ESI‐MS/MS of the original compound, which provides information about the amine moiety, and ESI‐MS/MS of the phosphonic acid hydrolysis products generated by N‐iodosuccinimide, which provides ions' characteristic of the phosphonate structure. This approach enables the structural elucidation of the original V‐agents with a higher degree of certainty. 相似文献
23.
Stahl F Moran D von Ragué Schleyer P Prall M Schreiner PR 《The Journal of organic chemistry》2002,67(5):1453-1461
Aromaticity criteria (magnetic susceptibility exaltations, nucleus independent chemical shifts (NICS), and aromatic stabilization energy (ASE) evaluations) for enediyne and enyne-allene cyclizations evaluated at (UBS)-BLYP/6-31G* all agree that the degrees of cyclic electron delocalization of the benzenoid systems formed by the Bergman (3) and Myers-Saito reactions (5) are comparable to benzene. The reaction enthalpy differences between the parent cyclizations and their benzannelated analogues are not entirely due to disparities in gained ASE during the reactions. The alternative formation of fulvene biradicals is not accompanied by favorable aromatic effects. 相似文献
24.
The dependence of ultrasound contrast agents backscatter on acoustic pressure: theory versus experiment 总被引:2,自引:0,他引:2
Experimental investigations have not fully explored the interaction between ultrasound beams and microbubble contrast agents. Moreover theoretical investigations have not solved the problem of the microbubble oscillation. A simple in-vitro system based on a commercial scanner (ATL UM9) was used to insonate (3 MHz transmission) diluted contrast suspensions of Definity and Quantison at different acoustic pressures (0.27-1.52 MPa). The experimental data were referred to a blood mimicking fluid in order to extract an estimate of their scattering cross-section. The results were compared with the solutions of the three main bubble oscillatidn models, Rayleigh-Plesset, Herring and Gilmore. Non-linear solutions of the above models were produced numerically using the Mathematica Package Software. The experiments showed that both agents provided a linear increase in scattering cross-section with increasing acoustic pressure. The thick shelled Quantison provided an increasing number of scatterers with increasing acoustic pressure, which proved that free bubbles leaked out of the shell. At high acoustic pressures both Quantison and Definity scattering cross-sections were almost identical, and were probably that of a free bubble. The Rayleigh-Plesset model provided a scattering cross-section almost independent of acoustic pressure. On the contrary the scattering cross-sections calculated by the Herring and Gilmore models solutions displayed a definite dependence on acoustic pressure of an order higher than one, which is slightly higher than the order of dependence exhibited by the experimental data. However, the increase of the experimentally measured scattering cross-section with acoustic pressure was sharper than the calculated one by the above two models. This is most probably due to the fact that the models simulated damped and not free bubble oscillations. In conclusion the Rayleigh-Plesset model was inadequate in describing the bubble oscillations even at small diagnostic acoustic pressures. The Herring and Gilmore models could simulate the dependence of the scattering cross-section of encapsulated microbubbles on acoustic pressure. However the contribution of free bubble oscillations has still to be modelled. 相似文献
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We present a theoretical and numerical modeling study of the multiphysicochemical process in electrokinetic transport in silica nanochannels. The electrochemical boundary condition is solved by considering both the chemical equilibrium on solid-liquid interfaces and the salt concentration enrichment caused by the double layer interaction. The transport behavior is modeled numerically by solving the governing equations using the lattice Poisson-Boltzmann method. The framework is validated by good agreements with the experimental data for all range of ionic concentrations. The modeling results suggest that when the double layers interact, the bulk salt concentration enrichment results in the saturation of conductances for low ionic concentrations. Both the streaming conductance and the electrical conductance are enhanced by the double layer interaction, and such enhancements diminish when the channel size is larger than 10 times of the Debye length. The streaming conductance increases with pH almost linearly when pH < 8, while the electrical conductance increases with pH exponentially. 相似文献
30.
Hurth C Smith SD Nordquist AR Lenigk R Duane B Nguyen D Surve A Hopwood AJ Estes MD Yang J Cai Z Chen X Lee-Edghill JG Moran N Elliott K Tully G Zenhausern F 《Electrophoresis》2010,31(21):3510-3517
The microfluidic integration of an entire DNA analysis workflow on a fully integrated miniaturized instrument is reported using lab‐on‐a‐chip automation to perform DNA fingerprinting compatible with CODIS standard relevant to the forensic community. The instrument aims to improve the cost, duration, and ease of use to perform a “sample‐to‐profile” analysis with no need for human intervention. The present publication describes the operation of the three major components of the system: the electronic control components, the microfluidic cartridge and CE microchip, and the optical excitation/detection module. Experimental details are given to characterize the level of performance, stability, reliability, accuracy, and sensitivity of the prototype system. A typical temperature profile from a PCR amplification process and an electropherogram of a commercial size standard (GeneScan 500?, Applied Biosystems) separation are shown to assess the relevance of the instrument to forensic applications. Finally, we present a profile from an automated integrated run where lysed cells from a buccal swab were introduced in the system and no further human intervention was required to complete the analysis. 相似文献