共查询到20条相似文献,搜索用时 12 毫秒
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Nobutaka Fujieda Kyohei Umakoshi Yuta Ochi Yosuke Nishikawa Sachiko Yanagisawa Minoru Kubo Genji Kurisu Shinobu Itoh 《Angewandte Chemie (International ed. in English)》2020,59(32):13385-13390
The dinuclear copper enzyme, tyrosinase, activates O2 to form a (μ‐η2:η2‐peroxido)dicopper(II) species, which hydroxylates phenols to catechols. However, the exact mechanism of phenolase reaction in the catalytic site of tyrosinase is still under debate. We herein report the near atomic resolution X‐ray crystal structures of the active tyrosinases with substrate l ‐tyrosine. At their catalytic sites, CuA moved toward l ‐tyrosine (CuA1 → CuA2), whose phenol oxygen directly coordinates to CuA2, involving the movement of CuB (CuB1 → CuB2). The crystal structures and spectroscopic analyses of the dioxygen‐bound tyrosinases demonstrated that the peroxide ligand rotated, spontaneously weakening its O?O bond. Thus, the copper migration induced by the substrate‐binding is accompanied by rearrangement of the bound peroxide species so as to provide one of the peroxide oxygen atoms with access to the phenol substrate's ? carbon atom. 相似文献
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Dr. Isaac Garcia‐Bosch Maxime A. Siegler 《Angewandte Chemie (International ed. in English)》2016,55(41):12873-12876
Copper complexes bearing readily available ligand systems catalyzed the oxidation of alkanes with H2O2 as the oxidant with high efficiency in remarkable yields (50–60 %). The reactions proceeded with unprecedented selectivity to give alkyl hydroperoxides as the major products. Detailed scrutiny of the reaction mechanism suggests the involvement of C‐centered and O‐centered radicals generated in a Fenton‐like fashion. 相似文献
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Kensaku Hirose Prof. Dr. Kei Ohkubo Prof. Dr. Shunichi Fukuzumi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12904-12909
Hydroxylation of benzene by molecular oxygen (O2) occurs efficiently with 10‐methyl‐9,10‐dihydroacridine (AcrH2) as an NADH analogue in the presence of a catalytic amount of Fe(ClO4)3 or Fe(ClO4)2 with excess trifluoroacetic acid in a solvent mixture of benzene and acetonitrile (1:1 v/v) to produce phenol, 10‐methylacridinium ion and hydrogen peroxide (H2O2) at 298 K. The catalytic oxidation of benzene by O2 with AcrH2 in the presence of a catalytic amount of Fe(ClO4)3 is started by the formation of H2O2 from AcrH2, O2, and H+. Hydroperoxyl radical (HO2.) is produced from H2O2 with the redox pair of Fe3+/Fe2+ by a Fenton type reaction. The rate‐determining step in the initiation is the proton‐coupled electron transfer from Fe2+ to H2O2 to produce HO. and H2O. HO. abstracts hydrogen rapidly from H2O2 to produce HO2. and H2O. The Fe3+ produced was reduced back to Fe2+ by H2O2. HO2. reacts with benzene to produce the radical adduct, which abstracts hydrogen from AcrH2 to give the corresponding hydroperoxide, accompanied by generation of acridinyl radical (AcrH.) to constitute the radical chain reaction. Hydroperoxyl radical (HO2.), which was detected by using the spin trap method with EPR analysis, acts as a chain carrier for the two radical chain pathways: one is the benzene hydroxylation with O2 and the second is oxidation of an NADH analogue with O2 to produce H2O2. 相似文献
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Dr. Isaac Garcia‐Bosch Dr. Ryan E. Cowley Daniel E. Díaz Maxime A. Siegler Prof. Wonwoo Nam Prof. Edward I. Solomon Prof. Kenneth D. Karlin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(15):5133-5137
We report the CuI/O2 chemistry of complexes derived from the macrocylic ligands 14‐TMC (1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane) and 12‐TMC (1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane). While [(14‐TMC)CuI]+ is unreactive towards dioxygen, the smaller analog [(12‐TMC)CuI(CH3CN)]+ reacts with O2 to give a side‐on bound peroxo‐dicopper(II) species (SP), confirmed by spectroscopic and computational methods. Intriguingly, 12‐TMC as a N4 donor ligand generates SP species, thus in contrast with the previous observation that such species are generated by N2 and N3 ligands. In addition, the reactivity of this macrocyclic side‐on peroxo‐dicopper(II) differs from typical SP species, because it reacts only with acid to release H2O2, in contrast with the classic reactivity of Cu2O2 cores. Kinetics and computations are consistent with a protonation mechanism whereby the TMC acts as a hemilabile ligand and shuttles H+ to an isomerized peroxo core. 相似文献
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Simplest Monodentate Imidazole Stabilization of the oxy‐Tyrosinase Cu2O2 Core: Phenolate Hydroxylation through a CuIII Intermediate 下载免费PDF全文
Dr. Linus Chiang William Keown Dr. Cooper Citek Dr. Erik C. Wasinger Prof. T. Daniel P. Stack 《Angewandte Chemie (International ed. in English)》2016,55(35):10453-10457
Tyrosinases are ubiquitous binuclear copper enzymes that oxygenate to CuII2O2 cores bonded by three histidine Nτ‐imidazoles per Cu center. Synthetic monodentate imidazole‐bonded CuII2O2 species self‐assemble in a near quantitative manner at ?125 °C, but Nπ‐ligation has been required. Herein, we disclose the syntheses and reactivity of three Nτ‐imidazole bonded CuII2O2 species at solution temperatures of ?145 °C, which was achieved using a eutectic mixture of THF and 2‐MeTHF. The addition of anionic phenolates affords a CuIII2O2 species, where the bonded phenolates hydroxylate to catecholates in high yields. Similar CuIII2O2 intermediates are not observed using Nπ‐bonded CuII2O2 species, hinting that Nτ‐imidazole ligation, conserved in all characterized Ty, has functional advantage beyond active‐site flexibility. Substrate accessibility to the oxygenated Cu2O2 core and stabilization of a high oxidation state of the copper centers are suggested from these minimalistic models. 相似文献
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New Copper,Palladium and Nickel Catalytic Systems: An Evolution towards More Efficient Procedures 下载免费PDF全文
Raul SanMartin María Teresa Herrero Esther Domínguez 《Chemical record (New York, N.Y.)》2016,16(3):1082-1095
Metal‐catalysed reactions are a fundamental tool in synthetic chemistry. Increasingly challenging transformations can be accomplished only by means of certain metal catalysts. However, there still remains the need for a substantial decrease of the amount of catalyst, for better reuse or recycling of such active species, and for the avoidance of relatively toxic solvents in favour of environmentally friendly media. These facts apply to copper‐, palladium‐, and nickel‐catalysed cross‐coupling reactions, direct arylations, and oxidative processes. This account summarises our research on the last reactions, featuring an evolution towards more sustainable procedures in this field. 相似文献
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本文采用静态水热合成法合成了一种非水溶性固体铜铝磷酸盐(CuAlPO).研究结果发现,CuAlPO是一种与六方二氧化硅(SiO2)晶体结构相同的新型铜铝磷盐,在温和反应条件下(30℃),CuAlPO具有较高的苯酚催化羟化反应活性. 相似文献
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Unsymmetrical Binding Modes of the HOPNO Inhibitor of Tyrosinase: From Model Complexes to the Enzyme
Dr. Constance Bochot Dr. Elisabeth Favre Dr. Carole Dubois Dr. Benoit Baptiste Prof. Luigi Bubacco Prof. Pierre‐Alain Carrupt Gisèle Gellon Dr. Renaud Hardré Prof. Dominique Luneau Dr. Yohann Moreau Dr. Alessandra Nurisso Dr. Marius Réglier Prof. Guy Serratrice Dr. Catherine Belle Dr. Hélène Jamet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3655-3664
The deciphering of the binding mode of tyrosinase (Ty) inhibitors is essential to understand how to regulate the tyrosinase activity. In this paper, by combining experimental and theoretical methods, we studied an unsymmetrical tyrosinase functional model and its interaction with 2‐hydroxypyridine‐N‐oxide (HOPNO), a new and efficient competitive inhibitor for bacterial Ty. The tyrosinase model was a dinuclear copper complex bridged by a chelated ring with two different complexing arms (namely (bis(2‐ethylpyridyl)amino)methyl and (bis(2‐methylpyridyl)amino)methyl). The geometrical asymmetry of the complex induces an unsymmetrical binding of HOPNO. Comparisons have been made with the binding modes obtained on similar symmetrical complexes. Finally, by using quantum mechanics/molecular mechanics (QM/MM) calculations, we studied the binding mode in tyrosinase from a bacterial source. A new unsymmetrical binding mode was obtained, which was linked to the second coordination sphere of the enzyme. 相似文献
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Xing Yue WEI Sheng Ying QIN College of Environmental Biological Engineering Chongqing Technology Business University Chongqing Department of Chemistry Sichuan University Chengdu 《中国化学快报》2006,(9)
Synthetic oxygen carriers are of great interest as models to mimic oxygen-carrying metalloenzymes for oxygen storage and transport1,2. Moreover, they possess great significance to realize high efficiency and selectivity catalytic oxidation of organic subs… 相似文献
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Dr. Danila Gasperini Dr. Mark D. Greenhalgh Rehan Imad Shezaib Siddiqui Anum Malik Fizza Arshad Prof. Muhammad Iqbal Choudhary Prof. Abdullah M. Al-Majid Dr. David B. Cordes Prof. Alexandra M. Z. Slawin Prof. Steven P. Nolan Prof. Andrew D. Smith 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(4):1064-1075
During an investigation into the potential union of Lewis basic isothiourea organocatalysis and gold catalysis, the formation of gold-isothiourea complexes was observed. These novel gold complexes were formed in high yield and were found to be air- and moisture stable. A series of neutral and cationic chiral gold(I) and gold(III) complexes bearing enantiopure isothiourea ligands was therefore synthesized and fully characterized. The steric and electronic properties of the isothiourea ligands was assessed through calculation of their percent buried volume and the synthesis and analysis of novel iridium(I)-isothiourea carbonyl complexes. The novel gold(I)- and gold(III)-isothiourea complexes have been applied in preliminary catalytic and biological studies, and display promising preliminary levels of catalytic activity and potency towards cancerous cell lines and clinically relevant enzymes. 相似文献
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DaiRongYUAN JiaMingYAN ChengZhiYU RuGangXIE 《中国化学快报》2005,16(2):147-150
A series of tyrosinase model ligands and complexes containing polyimidazoles were prepared. 2, 4-Di-tert-butyl-phenol was ortho-hydroxylated by the binuclear copper (I) complex [Cu2(6a)(CH3CN)2](ClO4)2 8a and molecular dioxygen under mild conditions with up to 80.4% yield, 91.4% selectivity and 92.0% conversion. 相似文献
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Prof. Dr. Sunney I. Chan Yu‐Jhang Lu Dr. Penumaka Nagababu Dr. Suman Maji Mu‐Cheng Hung Marianne M. Lee Prof. Dr. I‐Jui Hsu Pham Dinh Minh Jeff C.‐H. Lai Kok Yoah Ng Sridevi Ramalingam Prof. Dr. Steve S.‐F. Yu Prof. Dr. Michael K. Chan 《Angewandte Chemie (International ed. in English)》2013,52(13):3731-3735
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ChunChunZHANG WeiZENG JianZhangLI ShengYingQIN 《中国化学快报》2003,14(6):627-630
The oxygenation of cobalt(Ⅱ) hydroxamates(CoL2) and its catalytic performance in oxidation of p-xylene to p-toluic acid (PTA) were examined.The effects of X and Y bonded to hydroxamate group on dioxygen affinities and catalytic oxidation performance were also investigated. 相似文献
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Brian V. Popp Dr. Shannon S. Stahl Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(12):2915-2922
Aerobic oxidation : Mechanisms of aerobic oxidation of the PdII(OAc)2/pyridine catalyst system were evaluated by using density functional theory methods. The results reveal that labile monodentate ligands, such as pyridine, favor a catalyst reoxidation pathway that proceeds via Pd0, rather than direct reaction of O2 with a PdII–hydride intermediate (see scheme).