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61.
Melvyn Rowen Churchill David George Churchill My Hang Vo Huynh Kenneth J. Takeuchi 《Journal of chemical crystallography》2000,30(1):17-21
The complex cis-[Ru(bpy)2{PMe(o-tol)2}Cl+][ClO–
4] crystallizes in space group P21/c witha = 9.375(2) Å, b = 22.019(7) Å, c = 16.153(4) Å, = 90.83(2)°, V = 3333.9(16) Å3 and D(calc'd) = 1.547 g/cm3 for Z = 4. The Ru-PMe(o-tol)2 bond length of 2.357(3) Å is significantly longer than distances of Ru-PMe2(o-tol) = 2.324(2) Å and Ru-PMe3 = 2.310(2) Å in analogous complexes. The corresponding Ru-P(o-tol)3 complex has eluded synthesis, probably due to steric hindrance. 相似文献
62.
Backus EH Nguyen PH Botan V Moretto A Crisma M Toniolo C Zerbe O Stock G Hamm P 《The journal of physical chemistry. B》2008,112(48):15487-15492
Applying ultrafast vibrational spectroscopy, we find that vibrational energy transport along a helical peptide changes from inefficient but mostly ballistic below approximately 270 K into diffusive and significantly more efficient above. On the basis of molecular dynamics simulations, we attribute this change to the increasing flexibility of the helix above this temperature, similar to the glass transition in proteins. Structural flexibility enhances intramolecular vibrational energy redistribution, thereby refeeding energy into the few vibrational modes that delocalize over large parts of the structure and therefore transport energy efficiently. The paper outlines concepts how one might regulate vibrational energy transport properties in ultrafast photobiological processes, as well as in molecular electronic devices, by engineering the flexibility of their components. 相似文献
63.
Swarbhanu Sarkar Yeong Su Ha Nisarg Soni Gwang Il An Woonghee Lee Min Hwan Kim Phuong Tu Huynh Heesu Ahn Nikunj Bhatt Yong Jin Lee Jung Young Kim Kwon Moo Park Isao Ishii Shin‐Geol Kang Jeongsoo Yoo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(32):9511-9516
Hydrogen sulfide (H2S) has multifunctional roles as a gas signaling molecule in living systems. However, the efficient detection and imaging of H2S in live animals is very challenging. Herein, we report the first radioisotope‐based immobilization technique for the detection, quantification, and in vivo imaging of endogenous H2S. Macrocyclic 64Cu complexes that instantly reacted with gaseous H2S to form insoluble 64CuS in a highly sensitive and selective manner were prepared. The H2S concentration in biological samples was measured by a thin‐layer radiochromatography method. When 64Cu–cyclen was injected into mice, an elevated H2S concentration in the inflamed paw was clearly visualized and quantified by Cerenkov luminescence and positron emission tomography (PET) imaging. PET imaging was also able to pinpoint increased H2S levels in a millimeter‐sized infarcted lesion of the rat heart. 相似文献
64.
Nguyen Phuong Hanh Nguyen Huu Toan Phan Nguyen Thi Dieu Thuan Tran Thi Hong Hanh Le Thi Vien Nguyen Phuong Thao 《Natural product research》2016,30(18):2071-2076
Six iridoid derivatives (1–6), including two new compounds myrmecodoides A and B (1 and 2), were isolated from the ant-plant Myrmecodia tuberosa. Their structures were determined on the basis of spectroscopic data (1H and 13C NMR, HSQC, HMBC, 1H-1H COSY, NOESY and HR-ESI-MS) and by comparison with the literature values. Among isolates, 3 and 4 exhibit weak antibacterial effect against Staphylococcus aureus subsp. aureus with MIC value of 100.0 μg/mL. 相似文献
65.
All higher life forms use oxygen and respiration as their primary energy source. The oxygen comes from water by solar-energy conversion in photosynthetic membranes. In green plants, light absorption in photosystem II (PSII) drives electron-transfer activation of the oxygen-evolving complex (OEC). The mechanism of water oxidation by the OEC has long been a subject of great interest to biologists and chemists. With the availability of new molecular-level protein structures from X-ray crystallography and EXAFS, as well as the accumulated results from numerous experiments and theoretical studies, it is possible to suggest how water may be oxidized at the OEC. An integrated sequence of light-driven reactions that exploit coupled electron-proton transfer (EPT) could be the key to water oxidation. When these reactions are combined with long-range proton transfer (by sequential local proton transfers), it may be possible to view the OEC as an intricate structure that is "wired for protons". 相似文献
66.
The phi,psi backbone angle distribution of small homopolymeric model peptides is investigated by a joint molecular dynamics (MD) simulation and heteronuclear NMR study. Combining the accuracy of the measured scalar coupling constants and the atomistic detail of the all-atom MD simulations with explicit solvent, the thermal populations of the peptide conformational states are determined with an uncertainty of <5 %. Trialanine samples mainly ( approximately 90%) a poly-l-proline II helix-like structure, some ( approximately 10%) beta extended structure, but no alphaR helical conformations. No significant change in the distribution of conformers is observed with increasing chain length (Ala(3) to Ala(7)). Trivaline samples all three major conformations significantly. Triglycine samples the four corner regions of the Ramachandran space and exists in a slow conformational equilibrium between the cis and trans conformation of peptide bonds. The backbone angle distribution was also studied for the segment Ala3 surrounded by either three or eight amino acids on both N- and C-termini from a sequence derived from the protein hen egg white lysozyme. While the conformational distribution of the central three alanine residues in the 9mer is similar to that for the small peptides Ala(3)-Ala(7), major differences are found for the 19mer, which significantly (30-40%) samples alphaR helical stuctures. 相似文献
67.
68.
Bäckström D Moberg M Sjöberg PJ Bergquist J Danielsson R 《Journal of chromatography. A》2007,1171(1-2):69-79
Peptide mass fingerprints were obtained for three different proteins using three different digestion procedures in triplicates with liquid chromatography coupled to electrospray ionization mass spectrometry. For each protein the results were compared with multivariate data analysis (cluster analysis, kernel principal component analysis) and pair-wise contrast evaluation. Clear systematic differences between the digestion procedures were established for all the proteins. The visual presentation of the pair-wise differences between procedures could to some extent be related to the protein fragments, although the main objective was to identify m/z and retention regions in the original peptide maps that should be subject to further exploration. 相似文献
69.
70.
Phuong Y. Ghi David J. T. Hill Andrew K. Whittaker 《Journal of polymer science. Part A, Polymer chemistry》1999,37(19):3730-3737
The free radical copolymerizations of hydroxyethyl methacrylate and tetrahydrofurfuryl methacrylate have been investigated at 50°C. The compositions of polymers prepared at low conversions have been determined using 13C-NMR, and the glass transition temperatures determined by DSC. The copolymerizations were found to be best described by a terminal model with reactivity ratios of rH = 1.79 and rT = 0.76. The triad fraction sequence distributions have been calculated based on the terminal model and the calculated reactivity ratios. The glass transitions have been fitted to the Gordon–Taylor equation. The best value of the Gordon–Taylor constant was found to be kH = 1.42 ± 0.2, indicating nonideal mixing of the two monomer components in the copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3730–3737, 1999 相似文献