Yano Junko, Kern Jan, Pushkar Yulia, Sauer Kenneth, Glatzel Pieter, Bergmann Uwe, Messinger Johannes, Zouni Athina, Yachandra Vittal K
Melvin Calvin Laboratory, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Philos Trans R Soc Lond B Biol Sci. 2008 Mar 27;363(1494):1139-47; discussion 1147. doi: 10.1098/rstb.2007.2209.
The application of high-resolution X-ray spectroscopy methods to study the photosynthetic water oxidizing complex, which contains a unique hetero-nuclear catalytic Mn4Ca cluster, is described. Issues of X-ray damage, especially at the metal sites in the Mn4Ca cluster, are discussed. The structure of the Mn4Ca catalyst at high resolution, which has so far eluded attempts of determination by X-ray diffraction, X-ray absorption fine structure (EXAFS) and other spectroscopic techniques, has been addressed using polarized EXAFS techniques applied to oriented photosystem II (PSII) membrane preparations and PSII single crystals. A review of how the resolution of traditional EXAFS techniques can be improved, using methods such as range-extended EXAFS, is presented, and the changes that occur in the structure of the cluster as it advances through the catalytic cycle are described. X-ray absorption and emission techniques (XANES and Kbeta emission) have been used earlier to determine the oxidation states of the Mn4Ca cluster, and in this report we review the use of X-ray resonant Raman spectroscopy to understand the electronic structure of the Mn4Ca cluster as it cycles through the intermediate S-states.
描述了高分辨率X射线光谱学方法在研究光合水氧化复合物中的应用，该复合物包含一个独特的异核催化Mn4Ca簇。讨论了X射线损伤问题，特别是在Mn4Ca簇中的金属位点处的损伤。迄今为止，通过X射线衍射、X射线吸收精细结构（EXAFS）和其他光谱技术测定Mn4Ca催化剂高分辨率结构的尝试均未成功，现在已使用偏振EXAFS技术应用于定向光系统II（PSII）膜制剂和PSII单晶来解决这一问题。本文介绍了如何使用诸如扩展范围EXAFS等方法来提高传统EXAFS技术的分辨率，并描述了该簇在催化循环过程中结构发生的变化。X射线吸收和发射技术（XANES和Kβ发射） earlier已用于确定Mn4Ca簇的氧化态，在本报告中，我们回顾了使用X射线共振拉曼光谱来了解Mn4Ca簇在通过中间S态循环时的电子结构。 （注：原文中“earlier”位置似乎有误，翻译时按其所在位置直接译出）
