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XAFS Study of Coordination Structure of Cu(L-His)2 in Solution
Yan Pan1, Li-yun Zhang2, Yang-zhong Liu*1
1.Department of Chemistry, University of Science and Technology of China, Hefei 230026, China;2.National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Abstract:
Multiple coordination modes are present in the CuII-histidine complex in solution and the copper coordination environment varies with pH. In this work, we have investigated the coordination geometry of Cu(His)2 complex using X-ray absorption fine structure (XAFS) analysis. Copper K-edge XAFS spectra were acquired on aqueous Cu2+ samples with his-tidine at different pH values. The coordination environments were further confirmed by chemically modified histidine. Results show that the caboxylate groups coordinate at acidic condition, while amino and imidazole nitrogens get coordinated at higher pH. For the co-ordination geometry of Cu(His)2 in solution at physiological pH, the sixfold coordination is preferentially formed, while the fivefold coordination can co-exist in equilibrium.
Key words:  X-ray absorption fine structure, Coordination structure, Copper, Histidine, Chemical modification, pH
FundProject:
Cu(L-His)2溶液配位结构的X射线吸收精细结构分析
潘妍1, 张立云2, 刘扬中*1
1.中国科学技术大学化学系,合肥230026;2.中国科学技术大学同步辐射国家实验室,合肥230029
摘要:
采用X射线吸收精细结构分析(XAFS)方法分析Cu(His)2复合物的配位模式,通过测定不同pH值下的铜的K边XAFS吸收谱,研究Cu(His)2第一配位壳层的结构.为了更准确地验证Cu(His)2配位结构,对组氨酸的羧基和咪唑分别进行了化学修饰.研究结果明确了在不同pH环境下组氨酸的羧基、氨基和咪唑的配位情况.对于争议最大的在生理pH值下组氨酸的配位方式,其结果更支持六配位模式,同时可能有少量的五配位模式配合物平衡存在.
关键词:  X射线吸收精细结构,配位结构,铜离子,组氨酸,化学修饰,pH
DOI:10.1088/1674-0068/24/04/451-456
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