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排序方式: 共有540条查询结果,搜索用时 15 毫秒
11.
12.
Bo Huang Hirokazu Kobayashi Tomokazu Yamamoto Takaaki Toriyama Syo Matsumura Yoshihide Nishida Katsutoshi Sato Katsutoshi Nagaoka Masaaki Haneda Wei Xie Yusuke Nanba Michihisa Koyama Fenglong Wang Shogo Kawaguchi Yoshiki Kubota Hiroshi Kitagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2252-2257
Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru. Performance‐improved and cost‐reduced solid‐solution alloy nanoparticles of the Cu‐Ru system for CO oxidation are now presented. Over the whole composition range, all of the CuxRu1?x nanoparticles exhibit significantly enhanced CO oxidation activities, even at 70 at % of inexpensive Cu, compared to Ru nanoparticles. Only 5 at % replacement of Ru with Cu provided much better CO oxidation activity, and the maximum activity was achieved by 20 at % replacement of Ru by Cu. The origin of the high catalytic performance was found as CO site change by Cu substitution, which was investigated using in situ Fourier transform infrared spectra and theoretical calculations. 相似文献
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14.
Shin Iwata Kazunobu Toshima Shuichi Matsumura 《Macromolecular rapid communications》2003,24(7):467-471
Aliphatic polyesters containing thioester linkages were enzymatically prepared by both the copolymerization of lactone with mercaptoalkanoic acid and by the transesterification of polyesters with mercaptoalkanoic acids. The enzymatic copolymerization of ε‐caprolactone with 11‐mercaptoundecanoic acid (11MU) and 3‐mercaptopropionic acid (3MP) was performed under reduced pressure using an immobilized lipase from Candida antarctica (CA). The transesterification of poly(ε‐caprolactone) and poly[(R)‐3‐hydroxybutyrate] was carried out with 11MU and 3MP using lipase CA under reduced pressure.
15.
Miyoshi D Matsumura S Nakano S Sugimoto N 《Journal of the American Chemical Society》2004,126(1):165-169
Because of the importance of telomere DNAs, the structures of these DNAs in vivo are currently of great research interest in the medical, pharmaceutical, chemical, and industrial fields. To understand the structure of biomolecules in vivo, their properties studied in vitro are extrapolated to the in vivo condition, while the condition in a living cell is inherently molecularly crowded and a nonideal solution contains various biomolecules. We investigated the effect of molecular crowding, which is one of the most important cellular environmental conditions, on the structure and stability of the telomere and G-rich and C-rich DNAs using circular dichroism (CD) spectra, CD melting curves, and isothermal titration calorimetry (ITC). The CD spectra and CD melting curves of G-rich DNA, C-rich DNA, and the 1:1 mixture of G-rich and C-rich DNAs showed that each G-rich DNA, C-rich DNA, and the 1:1 mixture form the antiparallel G-quadruplex, I-motif, and duplex, respectively, in the noncrowding condition as previously considered. On the contrary, the G-rich and C-rich DNAs individually form the parallel G-quadruplex and I-motif, respectively, in the molecular crowding condition, and the 1:1 mixture folds into the parallel G-quadruplex and I-motif but does not form a duplex. The ITC measurements indicated that the thermodynamic stability (DeltaG degrees (20)) of the duplex formation between the G-rich and C-rich DNAs in the noncrowding condition was -10.2 kcal mol(-)(1), while only a small heat change was observed in the ITC measurements in the molecular crowding condition. These ITC results also demonstrated that the molecular crowding condition prevents any duplex formation between G-rich and C-rich DNAs. These results indicate that a structural polymorphism of the telomere DNAs is induced by molecular crowding in vivo. 相似文献
16.
The Electronic State of Hydrogen in the α Phase of the Hydrogen‐Storage Material PdH(D)x: Does a Chemical Bond Between Palladium and Hydrogen Exist? 下载免费PDF全文
Shun Dekura Prof. Hirokazu Kobayashi Prof. Ryuichi Ikeda Prof. Mitsuhiko Maesato Haruka Yoshino Prof. Masaaki Ohba Prof. Takayoshi Ishimoto Dr. Shogo Kawaguchi Prof. Yoshiki Kubota Dr. Satoru Yoshioka Prof. Syo Matsumura Prof. Takeharu Sugiyama Prof. Hiroshi Kitagawa 《Angewandte Chemie (International ed. in English)》2018,57(31):9823-9827
The palladium–hydrogen system is one of the most famous hydrogen‐storage systems. Although there has been much research on β‐phase PdH(D)x, we comprehensively investigated the nature of the interaction between Pd and H(D) in α‐phase PdH(D)x (x<0.03 at 303 K), and revealed the existence of Pd?H(D) chemical bond for the first time, by various in situ experimental techniques and first‐principles theoretical calculations. The lattice expansion, magnetic susceptibility, and electrical resistivity all provide evidence. In situ solid‐state 1H and 2H NMR spectroscopy and first‐principles theoretical calculations revealed that a Pd?H(D) chemical bond exists in the α phase, but the bonding character of the Pd?H(D) bond in the α phase is quite different from that in the β phase; the nature of the Pd?H(D) bond in the α phase is a localized covalent bond whereas that in the β phase is a metallic bond. 相似文献
17.
Noboru Matsumura Motoyuki Kusamiya Hiroo Inoue Masanori Yasui Fujiko Iwasaki 《Journal of heterocyclic chemistry》1995,32(4):1269-1275
1,3-Bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidinethiones 3a-f reacted with bromine to give trithiadiazapentalene derivatives 5a-f , bearing the exocyclic C-N double bonds, in moderate yields. The molecular structure of 5b was elucidated by the X-ray crystallographic analysis. The treatment of 5b-f with hydrochloric acid gave the ring-opening products, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazo-lidinones 9b-f , accompanied by the production of elemental sulfur. Reduction of 5b , 5d , and 5e with sodium borohydride gave the ring-opening compounds, 1,3-bis(p-substituted-phenylthiocarbamoyl)-2-imidazolidines 13b , 13d , and 13e respectively. 相似文献
18.
Fujiko Iwasaki Hideyuki Nishiyama Noriko Manabe Masanori Yasui Noboru Matsumura 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):429-430
Abstract Novel metal-carbene complexes (4) with a metallapentalene framework have been obtained from hypervalent diazadiselenathiapentalenes (3) by treating with Pt(PPh3)4, Pd(PPh3)4 and RhCl(PPh3)3. X-Ray investigations revealed that the central hypervalent sulfur atom in 3 was substituted by a metal atom to form M-Se bonds in the resultant metallapentalene framework. 相似文献
19.
Fumiko Fujisaki Sachi Hiromatsu Yumiko Matsumura Aki Fukami Nobuhiro Kashige Fumio Miake Kunihiro Sumoto 《Journal of heterocyclic chemistry》2013,50(2):417-424
In connection with our studies on antibacterial active compounds in the class of new oxazolidinones against Gram‐positive (Staphylococcus aureus) and Gram‐negative (Escherichia coli) strains, some molecular modifications were attempted. In this study, molecular modifications of 4‐aminomethyloxazolidin‐2‐ones ( 3a ) to the corresponding 4‐acylaminomethyloxazolidin‐2‐one derivatives ( 3c–d ) and preparations of the represented twin‐drug type molecules ( 10–14 ) were investigated. Some additional 4‐dialkylaminomethyloxazolidin‐2‐ones ( 2 ) were also synthesized. The synthesized compounds were evaluated for antibacterial activity with Gram‐positive (S. aureus) and Gram‐negative (E. coli) strains. 相似文献
20.
The direct enzymatic synthesis of a cyclic trimethylene carbonate (1,3‐dioxane‐2‐one) monomer with/without a methyl substituent was carried out using dimethyl or diethyl carbonate and 1,3‐diol with the objective of producing aliphatic poly(trimethylene carbonate), a typical biodegradable synthetic plastic. The lipase‐catalyzed condensation of dimethyl or diethyl carbonate with aliphatic 1,3‐diols using immobilized Candida antarctica lipase (lipase CA) in an organic solvent at 70 °C afforded the corresponding methyl‐substituted and unsubstituted cyclic trimethylene carbonates. The cyclic trimethylene carbonates obtained by the reaction of dimethyl or diethyl carbonates with 1,3‐propanediol and 2‐methyl‐1,3‐propanediol were polymerized by lipase to produce the corresponding polycarbonates.