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131.
Three new dimeric benzofuran derivatives, ligulacephalins A (1), B (2) and C (3), were isolated from the roots of Ligularia stenocephala MATSUM. ET KOIDZ. (Compositae) together with three known compounds, 5,6-dimethoxy-2-isopropenylbenzofuran (4), euparin (5) and (R)-(-)-hydroxytremetone (6). The structures of the new compounds were determined by spectroscopic evidence. The chiral HPLC analysis demonstrated that 1-3 occurred as a racemate. The absolute configurations of each enantiomer from 1-3 were elucidated on the basis of circular dichroism (CD) data. 相似文献
132.
O Matsumoto T Taga M Matsushima T Higashi K Machida 《Chemical & pharmaceutical bulletin》1990,38(8):2253-2255
The crystal of bovine trypsin complexed with a potent inhibitor, 4-[4-(N,N- dimethylcarbamoylmethoxycarbonylmethyl)phenoxycarbonylphenyl ]guanidinium (FOY-305) in the novel orthorhombic from with a low molecular packing density was studied by the X-ray diffraction method. Using synchrotron radiation, the intensity data were collected to 1.8 A resolution. The structure was solved by molecular replacement methods, and refined to an R-factor = 18.0% for 14364 reflections by the restrained least-squares method. The final difference Fourier maps revealed that hydrolyzed inhibitor fragments bind with the protein at multiple sites around the active center of trypsin. The structural feature in the crystalline state probably corresponds to a statistical average of several complexes which would be formed between the inhibitor and trypsin during the binding and releasing process in solution. 相似文献
133.
Susumu Honda Atsushi Taga Kazuaki Kakehi Shigetaka Koda Yoshihiko Okamoto 《Journal of chromatography. A》1992,590(2):364-368
Cefixime (CX), an oral cephalosporin antibiotic, and its metabolites in human digestive organs were separated by various modes of high-performance capillary electrophoresis. The zone electrophoresis mode in phosphate buffer (pH 6.8) containing 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulphonate gave the best separation, permitting the complete resolution of CX and all of five metabolites. On the other hand, the plain zone electrophoresis mode in phosphate buffer (pH 6.8) offered a simple procedure for the direct determination of urinary CX concentration using intact urine samples. 相似文献
134.
The mechanism of second H2O formation in fully reduced cytochrome c oxidase is examined by sequential additions of one electron and two protons to a [Fe(IV)O, Cu(II)] compound II, which is the final intermediate of first H2O formation. It is found that the addition of one electron induces the concerted proton–electron transfer from the CuB to FeO moieties with no energy barriers. The H2O molecule coordinating to the Cu atom is a key molecule for the proton transfer from the CuB moiety to the FeO and/or Fe–OH moieties. It is also found from the results in previous and the present works that one can realize the reduction process of dioxygen by fully reduced cytochrome c oxidase. 相似文献
135.
Seven new compounds were isolated from the roots of Ligularia dentata, including five bisabolane‐type sesquiterpenoids (bisabolane=1‐(1,5‐dimethylhexyl)‐4‐methylcyclohexane), namely (8β,10α)‐8‐(angeloyloxy)‐5,10‐epoxybisabola‐1,3,5,7(14)‐tetraene‐2,4,11‐triol ( 1 ), (8β,10α)‐8‐(angeloyloxy)‐5,10‐epoxythiazolo[5,4‐a]bisabola‐1,3,5,7(14)‐tetraene‐4,11‐diol ( 2 ), (1α,2α,3β,5α,6β)‐1,5,8‐tris(angeloyloxy)‐10,11‐epoxy‐2,3‐dihydroxybisabol‐7(14)‐en‐4‐one ( 3 ), (1α,2α,3β,5α,6β)‐2,5,8‐tris(angeloyloxy)‐10,11‐epoxy‐1,3‐dihydroxybisabol‐7(14)‐en‐4‐one ( 4 ), and (1α,2β,3β,5α,6β)‐1,8‐bis(angeloyloxy)‐2,3‐epoxy‐5,10‐dihydroxy‐11‐methoxybisabol‐7(14)‐en‐4‐one ( 5 ) (angeloyloxy=[(2Z)‐2‐methyl‐1‐oxobut‐2‐enyl]oxy), and two lactone derivatives, (2α,3β,5α)‐2‐(acetyloxy)‐9‐methoxy‐5‐(methoxycarbonyl)‐2,3‐dimethylheptano‐5‐lactone ( 6 ), and (2β,4β)‐2‐ethyl‐5‐hydroxy‐5‐(methoxycarbonyl)‐4,5‐dimethylpentano‐4‐lactone ( 7 ) (α/β denote relative configurations), together with (2E,4R,5S)‐2‐ethylidene‐5‐(methoxycarbonyl)‐4‐methylhexano‐5‐lactone ( 8 ), a known synthetic compound. Compound 2 is the first sesquiterpenoid derivative containing the uncommon benzothiazole moiety. The structures of 1 – 8 were established by spectroscopic methods, especially 2D‐NMR and MS analyses. 相似文献
136.
Application of integrated computer simulation approach to solid surfaces and interfaces 总被引:2,自引:0,他引:2
Abhijit Chatterjee Momoji Kubo Kazuo Teraishi Hiromitsu Takaba Yasunori Oumi Akira Miyamoto 《Catalysis Surveys from Japan》1998,2(2):133-153
The atomistic understanding of the structure, reactivity, and electronic properties of solid surfaces and interfaces are essential for the design of novel catalysts and electronics/photonics devices which have high-performance and unexplored properties. Computational chemistry is expected not only to rationalize the experimental results but also to predict new features. We have applied integrated computer simulation methods including quantum chemistry, periodic density functional theory, molecular dynamics, embedded atom method, and atomic force microscopy simulation to various topics related to solid surfaces and interfaces. In the present paper, we reviewed our recent activities on supported metal catalysts, metal clusters, atomic force microscopy simulation, high-temperature superconductors, tribology, Si semiconductor and V2O5 catalysts. Our activities also involve the generation of a lot of new computer simulation codes. We emphasize that the integrated computer simulation system provides not only methods for scientific studies but also a key technology for industrial innovations in research and development. 相似文献
137.
Chang CJ Nolan EM Jaworski J Okamoto K Hayashi Y Sheng M Lippard SJ 《Inorganic chemistry》2004,43(21):6774-6779
The synthesis of a difluorofluorescein monocarboxaldehyde platform and its use for preparing ZP8, a new member of the Zinpyr family of neuronal Zn(2+) sensors, are described. By combining an aniline photoinduced electron transfer (PET) switch and an electron-withdrawing fluorescein scaffold, ZP8 displays reduced background fluorescence and improved dynamic range compared to previous ZP probes. The bright sensor undergoes an 11-fold increase in fluorescence intensity upon Zn(2+) complexation (Phi = 0.03-0.35) with high selectivity over cellular concentrations of Ca(2+) and Mg(2+). In addition, sensors in the ZP family have been utilized for optical imaging in biological samples using two-photon microscopy (TPM). The cell-permeable ZP3 probe is capable of identifying natural pools of labile Zn(2+) within the mossy fiber synapses of live hippocampal slices using TPM, establishing the application of this technique for monitoring endogenous Zn(2+) stores. 相似文献
138.
Steven A. Markgraf Yasunori Furukawa Masayoshi Sato 《Journal of Crystal Growth》1994,140(3-4):343-348
We report on the top-seeded solution growth of LiB3O5 from an excess B2O3 solution. Parameters investigated include the Li2O/B2O3 ratio, rotation rate, pulling rate, cooling rate, and seed direction. With careful control of the above parameters, we have grown clear crystals of 25 × 30 × 20 mm in size. Selected nonlinear optical properties of these crystals are reported. Observations concerning the occurrence of unstable growth (inclusions, hopper growth) are discussed, and methods to eliminate the unstable growth are suggested. 相似文献
139.
Shizuo Tokito Hiromitsu Tanaka Koji Noda Akane Okada Yasunori Taga 《Macromolecular Symposia》1998,125(1):181-188
Novel hole and electron transporting materials have been synthesized to improve the thermal stability of organic electroluminescent (EL) devices. Molecular structures of such hole and electron transporting materials were designed based on triphenylamine (TPA) and oxadiazole (OXD) moieties, respectively. It has been found that the resulting materials have high glass transition temperatures (Tg) over 100°C and the vacuum-deposited thin films are significantly thermally stable. For the two-layer EL devices using the novel hole transporting materials and the typical emitting material, tris(8-quinolinolato) aluminum, the thermal stability has been clearly seen to depend on the Tg of the hole transporting material; excellent thermal stability was achieved. For the three-layer EL device using the novel electron transporting material, good emission efficiency and good stability were achieved. The electron transporting materials have been also applied to the polymeric system with polyvinylcarbazole matrix. 相似文献
140.
Hajime Yasuda Hitoshi Yamamoto Yasunori Takemoto Masahiro Yamashita Kiyohiko Yokota Shigenobu Miyake Akira Nakamura 《Macromolecular Symposia》1993,67(1):187-201
Organolanthanide(III) complexes such as |(C5Me55)2SmH|2 and (C5Me5)2SmMe(THF) were found to initiate the living polymerizations of methyl methacrylate (MMA) to give high molecular weight polymers (M n > 500 × 103) with extremely low polydispersity (M w/Mn = 1.04). The syndiotacticity increased up to 95.2% by lowering the temperature to −95°C. The molecular structure of the 1:2 adduct of (C5Me5)2SmH with MMA determined by X-ray method indicates that this intermediate assumes the 8 membered ring conformation where the Sm atom is bound to MMA in an enolate form and the ester of penultimate MMA is coordinated to the metal. Based upon these results, an anionic coordination mechanism has been proposed for the present reaction. Organolanthanide(II) complexes also exhibit high activity and proceed the living polymerizations. Organolanthanide(III) complexes also initiate the living polymerizations of lactones such as ϵ-caprolactone and δ-valerolactone. The stoichiometric reactions indicate that real active species assumes the alkoxylanthanide(III) form. 相似文献