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The mechanism of the action of copper-dependent quercetin 2,3-dioxygenase(2,3QD) has been investigated by means of hybrid density functional theory.The 2,3QD enzyme cleaves the O-heterocycle of a quercetin by incorporation of both oxygen atoms into the substrate and releases carbon monoxide.The calculations show that dioxygen attack on the copper complex is energetically favorable.The adduct has a possible near-degeneracy of states between [Cu 2+-(substrate-H +)] and [Cu +-(substrate-H).],and in addition the pyramidalized C 2 atom is ideally suited for forming a dioxygen-bridged structure.In the next step,the C 3-C 4 bond is cleaved and intermediate Int 5 is formed via transition state TS 4.Finally,the O a-O b and C 2-C 3 bonds are cleaved,and CO is released in one concerted transition state(TS 5) with the barrier of 63.25 and 61.91 kJ/mol in the gas phase and protein environments,respectively.On the basis of our proposed reaction mechanism,this is the rate-limiting step of the whole catalytic cycle and is strongly driven by a relatively large exothermicity of 100.86 kJ/mol.Our work provides some valuable fundamental insights into the behavior of this enzyme. 相似文献
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Science China Physics, Mechanics & Astronomy - A new numerical method-basic function method is proposed. This method can directly discrete differential operators on unstructured grids. By using... 相似文献
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DONG WenJun ZHAO HaiXin LI ChaoRong MEI Jie CHEN BeYong TANG WeiHua SHI Zhan & FENG ShouHua Center for Optoelectronics Materials Devices Center for Nanoscience Nanotechnology Key Laboratory of Advanced Textile Materials Manufacturing Technology Ministry of Education Engineering Research Center for Eco-Dying & Finishing of Textiles Zhejiang Sci-Tech University Hangzhou China State Key Laboratory of Inorganic Synthesis Preparative Chemistry College of Chemistry ... 《中国科学B辑(英文版)》2011,(6)
This paper reviews the recent research progress in the hetero-nanostructure of silver nanoparticles on MOx (M=Mo, Ti and Si). It describes the general synthesis of hetero-nanostructure of silver nanoparticles on MOx, and then outlines the interesting catalytic and sensing properties found in these hetero-nanostructures of silver nanoparticles on MOx. 相似文献
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本文推广了Bergweiler的一个正规定则:设α(z)和F分别是区域D上的非常数解析函数与解析函数族,R(z)是一个次数不低于2的有理函数.如果对族F中函数f(z)和g(z),Rof(z)和Rog(z)分担α(z)IM,并且下述条件之一成立:(1)对任意z0∈D,R(z)-α(z0)有至少两个不同的零点或极点;(2)存在z0∈D使得R(z)-α(z0):=P(z)Q(z)仅有一个零点(或极点)β0,同时k=lp(或k=lq),其中l和k分别是f(z)-β0和α(z)-α(z0)在z0处的零点重数,P(z)和Q(z)分别是次数为p和q的互质的多项式,并且α(z0)∈C∪{∞}.那么F在D内正规. 相似文献
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外缘烷基链长对共轭有机小分子聚集行为及光电性质影响 总被引:1,自引:0,他引:1
改变分子化学结构和调控分子结构聚集态行为从而影响或改变材料的化学和物理性质, 是开发新型高效有机光电功能材料的重要手段. 在共轭有机分子外缘引入烷基链一般是为了改进材料溶解性能, 但近来的一些研究表明, 烷基链长对一些共轭有机小分子固态聚集行为和光电性质具有重要影响, 烷基链扮演着显著调控材料光电性质的“功能基团”作用. 本文以聚集诱导发光(aggregation-induced emission, AIE)/聚集强化荧光(aggregation enhanced emission, AEE)发射共轭有机小分子为重点, 对近年来有关烷基链长对共轭有机分子聚集形态和光电性质影响的一些典型事例进行评述, 旨在使人们在进行共轭有机分子设计合成及其结构与性能关系研究中能够关注烷基链的因素, 使烷基链变化作为功能导向晶态共轭有机材料设计合成及其可控制备的一种手段. 相似文献
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Wang Li Zhao Bin Yuan ZhongYong Zhang XueJun Wu QingDuan Chang LiXian Zheng WenJun 《中国科学B辑(英文版)》2007,50(1):63-69
A simple and efficient approach is developed to fabricate single-crystalline CuO nanostructures through an ionic liquid assisted one-step low-temperature solid-state route.Both nanoparticles(5 nm in size)and nanorods(5-10 nm in diameter and 50-100 nm in length)of monoclinic CuO were obtained. These synthesized CuO nanostructures were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),selected area electron diffraction(SAED),X-ray photoelectron spectros- copy(XPS),energy dispersive spectroscopy(EDS)and nitrogen adsorption analysis.The morpholo- gies of the nanostructures can be controlled by tuning the amount of NaOH and ionic liquids.The growth mechanism of CuO nanostructures is investigated. 相似文献
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Reticular crack is generally found on the surface of ceramic material that has been subjected to a thermal-shock condition. In the present study, a quantitative effect of thermal shock and quench temperature has been studied and investigated. Experimental tests were carried out to characterize the reticular crack that has been found in the Ge Kiln, which is a famous art of the ancient Chinese culture. After comparative analysis between thermal-shock cracks and the glaze crack patterns of the Ge Kiln porcelain, it is found that this study is expected to provide a powerful tool for recurrence of the long-lost firing and cooling process of the Ge Kiln porcelain. 相似文献
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Porous tetragonal BaTiO 3 ceramic was successfully prepared by a combination of hydrothermal and low-temperature-sintering method.The hollow TiO2@BaCO 3 as the sintering precursor was synthesized via a simple hydrothermal method,and then porous BaTiO 3 was generated by calcining the hollow TiO2@BaCO 3 precursor at 900 ℃ without additive.The hollow TiO2@BaCO 3 structure plays two important roles in the preparing of the porous BaTiO 3 ceramic.First,the TiO2@BaCO 3 hollow structure provides high surface areas and increases the contact points between BaCO 3 and TiO2,which can reduce the sintering temperature of the BaTiO 3 ceramic.Second,the cavity of the ordered arranged TiO2@BaCO 3 hollow sphere shows important influence on the porous structure,and the pore size of the as-prepared porous BaTiO 3 ceramic can be tuned from several nanometers to hundreds nanomters by changing the sintering temperature.The formation mechanism of the porous BaTiO 3 ceramic was proposed. 相似文献