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41.
Directional crystallization from a binary mixture was performed by pseudo-NpT ensemble molecular dynamics. The initial crystal phase having a face-centered-cubic (fcc) structure grew toward the whole cell according to the temperature gradient in the universal cell. The growing crystal phase was not planar even though the solute molecules grew in two-dimensional coordinates because the solvent molecules disturbed the crystallization of the solute molecules at the diffusive crystal-solution interface. This represented the essential phenomenon of solute distribution during crystallization. Consequently, the growing crystal phase still contained solvent molecules having a liquid structure. The time change of the solute composition in the early phase of crystal growth showed an increase in solute composition as the time step proceeded. The resulting solute composition in this early phase was considered at different temperature gradients in the universal cell and it increased as the temperature of the initial crystal-solution interface increased. A new distribution coefficient model was proposed as a function of the difference between the local solute composition and bulk solute composition in the solution around the crystal-solution interface. The impurity-solvent distribution coefficient could be represented by the new model for faster growth of the lower temperature's initial interface. As regards a better distribution coefficient, there was found to be a very dilute solution phase over the crystal phase. The new variable "distribution rate" instead of the ambiguous variable "growth rate" was considered as a function of temperature gradient in the universal cell. 相似文献
42.
[Structure: see text] Beta-isocupreidine (beta-ICD)-catalyzed Baylis-Hillman reaction of chiral N-Boc-alpha-amino aldehydes and 1,1,1,3,3,3-hexafluoroisopropyl acrylate (HFIPA) takes place without racemization and exhibits the match-mismatch relationship between the substrate and the catalyst. In the case of acyclic amino aldehydes, L-substrates show excellent syn selectivity and high reactivity in contrast to D-substrates. On the other hand, in the case of cyclic amino aldehydes, D-substrates rather than L-substrates show excellent anti selectivity and high reactivity. 相似文献
43.
Kunishima M Tokaji M Matsuoka K Nishida J Kanamori M Hioki K Tani S 《Journal of the American Chemical Society》2006,128(45):14452-14453
Mere chemical generation of ceramide and related double-chain lipids in the membrane of small unilamellar vesicles (SUVs) induces fusion of the vesicles. The lipids can be successfully prepared by dehydrocondensation between single-chain lipids (fatty acids and sphingosine or its analogues) in a lipid bilayer of the SUV by using a combination of 2-chloro-4,6-dimethoxy-1,3,5-triazine and amphiphilic tertiary amine catalysts, a process that can be compared to a successive enzyme model system for a fatty acyl-CoA synthetase followed by acyltransferase. The SUV spontaneously undergoes membrane fusion upon this internal chemical stimulation by the artificial enzyme system. 相似文献
44.
Benfatto M Della Longa S Hatada K Hayakawa K Gawelda W Bressler C Chergui M 《The journal of physical chemistry. B》2006,110(29):14035-14039
A full multiple theoretical model (MXAN) is applied to fit picosecond difference X-ray absorption spectra at the ruthenium L(3) edge upon photoexcitation of aqueous [RuII(bpy)3]2+. We show that fitting difference spectra allows an increase in sensitivity, such that slight structural changes can be retrieved, which are not detected in fitting full spectra. The Ru-N bond distances of the excited complex in the (3)MLCT state are in good agreement with recently published values. The implementation of the present approach to L-edge spectra and its high sensitivity opens opportunities for its extension to a large class of experiments where difference X-ray absorption spectra are recorded. 相似文献
45.
Rachi T Kitajima M Kobayashi K Guo F Nakano T Ikemoto Y Kobayashi K Tanigaki K 《The Journal of chemical physics》2005,123(7):074503
The electronic states of Ba24Ge100 are studied by soft x-ray photoelectron spectroscopy (XPS) at a high-energy photon factory. A large reduction in the density of states (DOS) at the Fermi level is clearly shown before and after the electronic phase transition at 200 K. The changes in the spectrum widths and the fine structures of the core-level Ba 4d spectra give a very reasonable indication of the Ba-atom rattlings in the clathrate polyhedra. On-resonance experiments using the excitation from Ba 3d to 4f levels display that the wave functions of Ba 5d and 6s orbitals give only a small contribution to make a Fermi surface through the hybridization with the Ge20 cluster orbitals. Importantly, reliable values of the DOS at the Fermi level NEF are successfully deduced, using two data sets of DOS obtained from high-resolution XPS and the total magnetic susceptibilities by a superconducting quantum interference device, to be 0.149 and 0.0427 states eV(-1) (Ge atom)(-1) for a high-temperature and for a low-temperature phase. 相似文献
46.
Yoshimitsu Kohama Hitoshi Kawaji Keisuke Fukaya 《Journal of solid state chemistry》2009,182(6):1468-1472
Energy level diagrams have been determined for two molecular clusters, K12[(VO)3(SbW9O33)2]·15H2O and K12[(VO)3(BiW9O33)2]·29H2O, by low-temperature heat capacity measurements down to 85 mK under magnetic field strengths up to 9 T. Both compounds exhibit a broad heat capacity peak dependent upon the magnetic field, which can be explained by the thermal excitation in the magnetic energy levels. A detailed analysis based on the numerical calculation reveals that the spin-spin interaction between the V4+ ions includes a Dzyaloshinskii-Moriya interaction. 相似文献
47.
Amphiphilic copolymers using hydrophilic N,N‐dimethylacrylamide (DMA), hydrophobic methyl methacrylate (MMA) and a crosslinkable monomer, 3‐methacryloyloxypropyl trimethoxysilane (MTSi), were synthesized and evaluated as coating materials for leukocyte removal filters for whole blood. When filters composed of non‐woven fabrics were coated with crosslinked synthesized copolymers, the elution ratios of the copolymers to water were adequately low because of the crosslinking with trimethoxysilane groups of MTSi units in the copolymers. Filters coated with crosslinked poly(DMA‐co‐MTSi) having a 0.96 mole fraction of DMA units showed a 0.35 ± 0.44% platelet permeation ratio and a logarithmic reduction of 4.0 ± 0.68 for leukocytes. On the other hand, an increase in the content of MMA units in the DMA‐containing copolymers improved the permeation ratio of the platelets dramatically. Filters coated with crosslinked poly(DMA‐co‐MMA‐co‐MTSi) containing a 0.39 mole fraction of MMA units and a 0.58 mole fraction of DMA units showed an 86 ± 3.0% platelet permeation ratio and a logarithmic reduction of 2.1 ± 1.2 for leukocytes. This indicates that an adequate content of hydrophobic monomer units, such as MMA units, is necessary for effective platelet permeation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
48.
Watanuki S Matsuura K Tomura Y Okada M Okazaki T Ohta M Tsukamoto S 《Chemical & pharmaceutical bulletin》2011,59(8):1029-1037
A series of 1-isopropyl-1,2,3,4-tetrahydroisoquinoline derivatives were synthesized and their bradycardic activities were evaluated in isolated guinea pig right atria. Structure-activity relationship studies revealed that the introduction of an appropriate substituent and its position on the 1,2,3,4-tetrahydroisoquinoline ring are essential for potent in vitro activity. Furthermore, the tether between the piperidyl moiety and the terminal aromatic ring is important for potent antihypertensive activity. Oral administration of 6-fluoro-1-isopropyl-2-{[1-(2-phenylethyl)piperidin-4-yl]carbonyl}-1,2,3,4-tetrahydroisoquinoline (3b) to spontaneously hypertensive rats (SHR) elicited antihypertensive effects without inducing reflex tachycardia, which is often caused by traditional L-type Ca2? channel blockers. 相似文献
49.
Hiroshi Takikawa Arata Nishii Hiromu Takiguchi Hirotoshi Yagishita Masato Tanaka Keiichi Hirano Masanobu Uchiyama Ken Ohmori Keisuke Suzuki 《Angewandte Chemie (International ed. in English)》2020,59(30):12440-12444
An intramolecular benzyne–phenolate [4+2] cycloaddition is reported. Benzyne precursors, having vicinal halogen‐sulfonate functionalities, linked with a phenol(ate) by various tether groups undergo efficient intramolecular [4+2] cycloaddition by treatment with either Ph3MgLi or nBuLi for halogen–metal exchange to form various benzobarrelenes. 相似文献
50.
Experimental detection of proteolytic activity in a signal peptide peptidase of Arabidopsis thaliana
Hoshi Masako Ohki Yu Ito Keisuke Tomita Taisuke Iwatsubo Takeshi Ishimaru Yoshiro Abe Keiko Asakura Tomiko 《BMC biochemistry》2013,14(1):1-8