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排序方式: 共有297条查询结果,搜索用时 15 毫秒
51.
Fukushima T Arai K Tomiya M Mitsuhashi S Sasaki T Santa T Imai K Toyo'oka T 《Biomedical chromatography : BMC》2008,22(1):100-105
N-acetyl-L-aspartic acid (NAA) is an endogenous compound, and its brain concentration is suggested to be altered in neurological disorders. In the present study, a fluorescence determination method for NAA was developed by employing reversed-phase high-performance liquid chromatography (HPLC) with pre-column fluorescence derivatization using 4-N,N-dimethylaminosulfonyl-7-N-(2-aminoethyl)amino-2,1,3-benzoxadiazole (DBD-ED). Using methylsuccinic acid as the internal standard, a linear calibration curve for NAA was constructed in the range 125-1000 microM (n=3). The detection limit on the column was approximately 5.0 fmol (signal-to-noise ratio 3). The proposed HPLC method was applied to determine NAA in the rat cerebrum homogenate. Cerebrum NAA was successfully determined using 10 microL of the homogenate, and the validation data for the proposed HPLC method demonstrated satisfactory results. Intra- and inter-day precision and accuracy were within 1.1-7.0 and -8.1-6.3%, respectively. The concentration of NAA in the male rat cerebrum (13 weeks old) was 84+/-4.6 micromol/mg protein (n=3). 相似文献
52.
Dr. Kensuke Kiyokawa Miu Ishizuka Prof. Dr. Satoshi Minakata 《Angewandte Chemie (International ed. in English)》2023,62(12):e202218743
Oxycyanation of alkenes would allow the direct construction of useful β-hydroxy nitrile scaffolds. However, only limited examples of such reactions have been reported, and some problems including limited substrate scope and the lack of diastereocontrol in the case of the oxycyanation of internal alkenes have arisen. We herein report on the intermolecular oxycyanation of alkenes using p-toluenesulfonyl cyanide (TsCN) in the presence of tris(pentafluorophenyl)borane (B(C6F5)3) as a catalyst, affording products that contain a sulfinyloxy group and a cyano group at the vicinal position. The reaction features a stereospecific syn-addition. The reaction also shows a broad substrate scope with good functional group tolerance. Mechanistic investigations by experimental studies and density functional theory (DFT) calculations revealed that the reaction proceeds via an unprecedented stereospecific mechanism through the electrophilic cyanation of alkenes, in which B(C6F5)3 efficiently activates TsCN through the coordination of the cyano group to the boron center. 相似文献
53.
Taichi Mitsumoto Dr. Yuya Ashida Dr. Kazuya Arashiba Dr. Shogo Kuriyama Akihito Egi Prof. Dr. Hiromasa Tanaka Prof. Dr. Kazunari Yoshizawa Prof. Dr. Yoshiaki Nishibayashi 《Angewandte Chemie (International ed. in English)》2023,62(43):e202306631
We newly designed and prepared a novel molybdenum complex bearing a 4-[3,5-bis(trifluoromethyl)phenyl]pyridine-based PNP-type pincer ligand, based on the bond dissociation free energies (BDFEs) of the N−H bonds in molybdenum-imide complexes bearing various substituted pyridine-based PNP-type pincer ligands. The complex worked as an excellent catalyst toward ammonia formation from the reaction of an atmospheric pressure of dinitrogen with samarium diiodide as a reductant and water as a proton source under ambient reaction conditions, where up to 3580 equivalents of ammonia were formed based on the molybdenum atom of the catalyst. The catalytic activity was significantly improved by one order of magnitude larger than that observed when using the complex before modification. 相似文献
54.
Inside Cover: Direct Transformation of Molecular Dinitrogen into Ammonia Catalyzed by Cobalt Dinitrogen Complexes Bearing Anionic PNP Pincer Ligands (Angew. Chem. Int. Ed. 46/2016)
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55.
Kohei Yazaki Shogo Noda Yuya Tanaka Yoshihisa Sei Munetaka Akita Michito Yoshizawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(48):15255-15258
Preparation of molecular nanostructures with polyradical frameworks remains a significant challenge because of the limited synthetic accessibility which is entirely different from that of neutral and ionic ones. Herein we report the quantitative formation of a new M2L4 molecular capsule from metal ions and dihydrophenazine‐based ligands. The capsule has a spherical nanocavity (ca. 1 nm in diameter) enclosed by eight redox‐active, dihydrophenazine panels. Electrochemical oxidation of the capsule leads to the generation of multiple radical cations on the shell framework. Moreover, a stable tetra(radical cation) capsule can be reversibly obtained by chemical as well as electrochemical oxidation. 相似文献
56.
Direct Transformation of Molecular Dinitrogen into Ammonia Catalyzed by Cobalt Dinitrogen Complexes Bearing Anionic PNP Pincer Ligands
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Dr. Shogo Kuriyama Dr. Kazuya Arashiba Prof. Dr. Hiromasa Tanaka Yuki Matsuo Dr. Kazunari Nakajima Prof. Dr. Kazunari Yoshizawa Prof. Dr. Yoshiaki Nishibayashi 《Angewandte Chemie (International ed. in English)》2016,55(46):14291-14295
The direct formation of ammonia from molecular dinitrogen under mild reaction conditions was achieved by using new cobalt dinitrogen complexes bearing an anionic PNP‐type pincer ligand. Up to 15.9 equivalents of ammonia were produced based on the amount of catalyst together with 1.0 equivalent of hydrazine (17.9 equiv of fixed nitrogen atoms). 相似文献
57.
Mitsuhashi S Fukushima T Tomiya M Santa T Imai K Toyo'oka T 《Analytica chimica acta》2007,584(2):315-321
Kynurenine (KYN), a tryptophan metabolite, is a crucial compound for modulating neurotransmission because it can be metabolized in vivo into both quinolinic acid and kynurenic acid, which are the agonist and antagonist, respectively, of N-methyl-d-aspartate receptor. For the highly sensitive detection of KYN by high-performance liquid chromatography (HPLC), a fluorescence derivatization of KYN with a benzofurazan-type fluorogenic reagent, 4-N,N-dimethylaminosulfonyl-7-fluoro-2,1,3-benzoxadiazole (DBD-F) was investigated in the present study. KYN was derivatized with DBD-F (DBD-KYN) at 60 °C for 30 min, and separated on an octadecylsilica column with a gradient elution of the mobile phase, which consists of 0.1% formic acid in acetonitrile/methanol/water. DBD-KYN was detected fluorimetrically at 553 nm with an excitation wavelength of 431 nm. The limits of detection and quantification were approximately 0.30 pmol [signal-to-noise ratio (S/N) 3] and 1.0 pmol (S/N, 10) on column, respectively. Plasma KYN levels were successfully determined using 10 μL of rat plasma with satisfactory precision and accuracy. Intra- and inter-day precisions and accuracies were 1.7-6.8%, and −10 to 9.6%, respectively. KYN levels in plasma of male Sprague-Dawley rats (7 weeks old) were approximately 2.4 ± 0.32 μmol L−1 (n = 4). The proposed HPLC method was applied to determine KYN levels in the plasma of ketamine-treated rats—the animal model of schizophrenia. 相似文献
58.
59.
Koumura N Wang ZS Mori S Miyashita M Suzuki E Hara K 《Journal of the American Chemical Society》2006,128(44):14256-14257
We designed and synthesized new alkyl-functionalized organic dyes, MK-1 and MK-2, for dye-sensitized solar cells (DSSCs). Based on the MK-2 dye, a high performance of efficiency (eta, 7.7%; short-circuit current density Jsc = 14.0 mA cm-2, open-circuit voltage Voc = 0.74 V, and fill factor FF = 0.74) was achieved under AM 1.5 G irradiation (100 mW cm-2). Remarkably, the relatively higher Voc for DSSCs based on MK-1 and MK-2 dyes, which have long alkyl chains, were observed among the organic dyes caused by the increasing of the electron lifetime in the conduction band of TiO2. Our molecular design of alkyl-functionalized dyes strongly suggests the promising performance of molecular photovoltaics based on organic dyes. 相似文献
60.
Yamada M Hayashi K Hayashi H Tsuji R Kakumoto K Ikeda S Hoshino T Tsutsui K Tsutsui K Ito T Iinuma M Nozaki H 《Chemical & pharmaceutical bulletin》2006,54(3):354-358
Four new resveratrol oligomers, nepalensinols D-G, were isolated from the stem of Kobresia nepalensis (Cyperaceae). The structures were determined by detailed NMR spectral analysis. The compounds were assessed for their inhibitory activity against human topoisomerase II, a potential target of anti-tumor agents. These stilbenoids showed potent inhibitory activity against human topoisomerase II with IC50 values of 5-15 microM. 相似文献