A quantitative description of the ground-state wave function of CuA by X-ray absorption spectroscopy: Comparison to plastocyanin and relevance to electron transfer
A quantitative description of the ground-state wave function of CuA by X-ray absorption spectroscopy: Comparison to plastocyanin and relevance to electron transfer
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DOI：
10.1021/ja004109i
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发表时间：
2001-06-20
影响因子：
15
通讯作者：
Solomon, EI
中科院分区：
文献类型：
--
作者：
George, SD;Metz, M;Solomon, EI
为了评估CUA的电子结构对其电子转移（ET）功能的重要性，利用S K边和Cu L边X射线吸收光谱（XAS）对铜绿假单胞菌天青蛋白中的混合价（MV）双核Cu-A中心的基态波函数进行了定量描述.已经对双核硫醇盐桥接的MV参考模型络合物（[（（LCu）-Cu-iPrdacoS）（2）]（+））和同价（II，II）类似物（[（LCu）-Cu-iPr 2 tacnS）（2）]（2+）进行了平行描述，其中L-iPrdacoS和L-iPr 2 tacnS是具有桥接Cu离子的连接硫醇盐的大环配体。以前的研究定性地定义了地面凝视波函数的铜-A的配位场的轨道取向和存在的金属-金属键的影响。这里提出的研究提供了进一步的证据，直接铜-铜相互作用，重要的是，实验量化的共价基态波函数。DFT计算进一步支持了实验结果。的性质的基态波函数的铜-A相比，定义明确的蓝色铜网站plastocyanin。并讨论了该波函数对Cu-A较低的重组能和ET函数的重要性。该波函数将各向异性共价结合到细胞色素c氧化酶的分子内和分子间ET途径中。因此，Cys-Cu键的高共价性允许通过该配体的路径与从Cu-A到血红素a的分子内ET中的较短His路径竞争，并且对于激活从血红素c到CUA的分子间ET路径特别重要。
To evaluate the importance of the electronic structure of CUA to its electron-transfer (ET) function, a quantitative description of the ground-state wave function of the mixed-valence (MV) binuclear Cu-A center engineered into Pseudomonas aeruginosa azurin has been developed, using a combination of S K-edge and Cu L-edge X-ray absorption spectroscopies (XAS). Parallel descriptions have been developed for a binuclear thiolate-bridged MV reference model complex ([((LCu)-Cu-iPrdacoS)(2)](+)) and a homovalent (II,II) analogue ([(LCu)-Cu-iPr2tacnS)(2)](2+), where L-iPrdacoS and L-iPr2tacnS are macrocyclic ligands with attached thiolates that bridge the Cu ions. Previous studies have qualitatively defined the ground-stare wave function of Cu-A in terms of ligand field effects on the orbital orientation and the presence of a metal-metal bond. The studies presented here provide further evidence for a direct Cu-Cu interaction and, importantly, experimentally quantify the covalency of the ground-state wave function. The experimental results are further supported by DFT calculations. The nature of the ground-state wave function of Cu-A is compared to that of the well-defined blue copper site in plastocyanin. and the importance of this wave function to the lower reorganization energy and ET function of Cu-A is discussed. This wave function incorporates anisotropic covalency into the intra- and intermolecular ET pathways in cytochrome c oxidase. Thus, the high covalency of the Cys-Cu bond allows a path through this ligand to become competitive with a shorter His path in the intramolecular ET from Cu-A to heme a and is particularly important for activating the intermolecular ET path from heme c to CUA.