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排序方式: 共有2310条查询结果,搜索用时 146 毫秒
1.
Watanabe Sou Senzaki Tatsuya Shibata Atsuhiro Nomura Kazunori Takeuchi Masayuki Nakatani Kiyoharu Matsuura Haruaki Horiuchi Yusuke Arai Tsuyoshi 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1273-1277
Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate... 相似文献
2.
Dr. Kenta Arai Takahiko Matsunaga Haruhito Ueno Nozomi Akahoshi Yuumi Sato Dr. Gaurango Chakrabarty Prof. Dr. Govindasamy Mugesh Prof. Dr. Michio Iwaoka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(55):12751-12760
At the redox-active center of thioredoxin reductase (TrxR), a selenenyl sulfide (Se−S) bond is formed between Cys497 and Sec498, which is activated into the thiolselenolate state ([SH,Se−]) by reacting with a nearby dithiol motif ([SHCys59,SHCys64]) present in the other subunit. This process is achieved through two reversible steps: an attack of a cysteinyl thiol of Cys59 at the Se atom of the Se−S bond and a subsequent attack of a remaining thiol at the S atom of the generated mixed Se−S intermediate. However, it is not clear how the kinetically unfavorable second step progresses smoothly in the catalytic cycle. A model study that used synthetic selenenyl sulfides, which mimic the active site structure of human TrxR comprising Cys497, Sec498, and His472, suggested that His472 can play a key role by forming a hydrogen bond with the Se atom of the mixed Se−S intermediate to facilitate the second step. In addition, the selenenyl sulfides exhibited a defensive ability against H2O2-induced oxidative stress in cultured cells, which suggests the possibility for medicinal applications to control the redox balance in cells. 相似文献
3.
Xiaopei Li Tasuku Ogihara Prof. Dr. Manabu Abe Dr. Yasuyuki Nakamura Prof. Dr. Shigeru Yamago 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9846-9850
The effect of viscosity on the diffusion efficiency (Fdif) of an organic radical pair in a solvent cage and the termination mechanism, that is, the selectivity of disproportionation (Disp) and combination (Comb) of the geminated caged radical pair and the diffused radicals encountered, were investigated quantitatively by following the photolysis of dimethyl 2,2′-azobis(2-methylpropionate) (V-601) in the absence and presence of PhSD. Fdif and Disp/Comb selectivity outside the cage [Disp(dif)/Comb(dif)] are highly sensitive to the viscosity. In contrast, the Disp/Comb selectivity inside the cage [Disp(cage)/Comb(cage)] is rather insensitive. The difference in viscosity dependence between Disp(cage)/Comb(cage) and Disp(dif)/Comb(dif) is explained by the spin state of the radical pair inside and outside the cage and the spin state dependent configurational changes of the radical pair upon their collision. Given that the configurational change of the radicals associates the displacement and reorganization of solvents around the radicals, the termination outside the cage, which requires larger change than that inside the cage, is highly viscosity dependent. Furthermore, while the bulk viscosity of each solvent shows good correlation with Fdif and Disp/Comb selectivity, microviscosity is the better parameter predicting Fdif and Disp(dif)/Comb(dif) selectivity regardless of the solvents. 相似文献
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Synthesis,Structural Characterization and Reactivity of a Bis(phosphine)(silyl) Platinum(II) Complex
Yonghua Li Wenjin Zeng Wenyong Lai Shigeru Shimada Shi Wang Lianhui Wang Wei Huang 《中国化学》2015,33(10):1206-1210
Treatment of 1,2‐C6H4(SiH3)(SiH3) ( 1 ) with Pt(dmpe)(PEt3)2 (dmpe=Me2PCH2CH2PMe2) in the ratio of 1:1 leads to the complex {1,2‐C6H4(SiH2)(SiH2)}PtII (dmpe) ( 2 ), which can react with proton organic reagent bearing hydroxy group with low steric hindrance to form a tetra‐alkoxy substituted silyl platinum(II) compound ( 3 ). Compounds 2 and 3 are the very rare examples of silyl transition‐metal complexes derived from this chelating hydrosilane ligand. To the best of our knowledge, there are only 6 examples of silyl metal complexes prepared from this ligand with such structural features registered in the Cambridge Structural Database, among them, only one silyl platinum(II) compound is presented. The structures of complexes 2 and 3 were unambiguously determined by multinuclear NMR spectroscopic studies and single crystal X‐ray analysis. 相似文献
8.
Chiral Bis(imidazolidine)‐Derived NCN Pincer Rh Complex for Catalytic Asymmetric Mannich Reaction of Malononitrile with N‐Boc Imines 下载免费PDF全文
Prof. Dr. Takayoshi Arai Takuma Moribatake Prof. Dr. Hyuma Masu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10671-10675
Chiral bis(imidazolidine)‐derived NCN–rhodium complexes ([PhBidine‐RhX2] and [tBu‐PhBidine‐RhX2]) were prepared by a C?H insertion method, and the structures were unequivocally determined by X‐ray crystallographic analysis. The [tBu‐PhBidine‐Rh(OAc)2] complex smoothly catalyzed an asymmetric Mannich reaction of malononitrile with N‐Boc imines to give products in up to 94 % ee, which are useful for the synthesis of chiral α‐amino acids. 相似文献
9.
Ran Chen Dr. Nikoloz Nioradze Dr. Padmanabhan Santhosh Dr. Zhiting Li Dr. Sumedh P. Surwade Ganesh J. Shenoy David G. Parobek Min A. Kim Prof. Haitao Liu Prof. Shigeru Amemiya 《Angewandte Chemie (International ed. in English)》2015,54(50):15134-15137
High electrochemical reactivity is required for various energy and sensing applications of graphene grown by chemical vapor deposition (CVD). Herein, we report that heterogeneous electron transfer can be remarkably fast at CVD‐grown graphene electrodes that are fabricated without using the conventional poly(methyl methacrylate) (PMMA) for graphene transfer from a growth substrate. We use nanogap voltammetry based on scanning electrochemical microscopy to obtain very high standard rate constants k0≥25 cm s?1 for ferrocenemethanol oxidation at polystyrene‐supported graphene. The rate constants are at least 2–3 orders of magnitude higher than those at PMMA‐transferred graphene, which demonstrates an anomalously weak dependence of electron‐transfer rates on the potential. Slow kinetics at PMMA‐transferred graphene is attributed to the presence of residual PMMA. This unprecedentedly high reactivity of PMMA‐free CVD‐grown graphene electrodes is fundamentally and practically important. 相似文献
10.
Complexation of some lanthanide ions with poly(methacrylic acid) and its copolymers was studied by potentiometric titration. Poly [methacrylic acid-co-oligo(ethylene oxide)methacrylate] and poly(methacrylic acid-co-acrylamide) formed tris-carboxylate coordinate lanthanide complexes with large overall complexation constants, while poly-(methacrylic acid)s and copolymer with higher content of the methacrylic acid residue formed bis-coordinate ones. It was concluded that the comonomer residues in the copolymer chains decreased the steric hindrance for the complexation and/or acted as co-coordinating groups of the carboxylic group to lanthanide ions. Very large positive and favorable entropy changes were observed for the complexation with poly(methacrylic acid) and its copolymers. This contribution of thermodynamic parameters to the complexation was contrary to that for the analogous monomeric methacrylic acid complex and is assumed to be induced by dehydration of the polymers through the lanthanide ion complexation. 相似文献