Direct detection of oxygen ligation to the Mn(4)Ca cluster of photosystem II by X-ray emission spectroscopy.
Direct detection of oxygen ligation to the Mn(4)Ca cluster of photosystem II by X-ray emission spectroscopy.
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DOI：
10.1002/anie.200905366
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发表时间：
2010
影响因子：
16.6
通讯作者：
Bergmann, Uwe
中科院分区：
文献类型：
--
作者：
Pushkar, Yulia;Long, Xi;Glatzel, Pieter;Brudvig, Gary W.;Dismukes, G. Charles;Collins, Terrence J.;Yachandra, Vittal K.;Yano, Junko;Bergmann, Uwe
配体在无机体系和金属蛋白中的催化反应中通过键的形成和断裂、质子化和去质子化以及电子和自旋离域而发挥关键作用。有明确定义的元素特定的光谱处理，如X射线光谱和EPR光谱，以遵循金属催化位点的化学。然而，直接探测特定的配体原子，如C，N和O，特别是在一个大的蛋白质基质中，是具有挑战性的，因为它们在蛋白质中的丰度。FTIR和拉曼光谱以及配体敏感的EPR光谱技术如ENDOR和ESEEM已被应用于研究金属-配体相互作用。X射线吸收光谱（XAS）也可以探测配体环境;它的元素特异性使我们能够只关注催化金属位点，EXAFS和XANES提供金属配体距离，配位数和配体环境的对称性。然而，这些信息是有限的，因为不可能区分具有相似原子序数的配体元素（即C，N和O）。作为一种替代和更直接的方法来探测蛋白质基质中的特定金属配体化学，我们研究了X射线发射光谱（XES）的应用。使用这种技术，我们已经确定了光系统II（PS II），多亚基膜蛋白，催化光合作用中的水氧化反应的Mn 4Ca复合物的氧桥配体。[1]用锰XAS对催化机理进行了深入的研究。[2]然而，最根本的挑战是了解水分子如何连接到Mn 4Ca簇，以及在O2演化之前如何形成O键。[3-5]这意味着有必要监测氧配体的化学性质以了解其机制。XES是XAS的补充方法，具有直接探测连接模式的潜力。[6]在几条发射线中，Kβ1，3和Kβ 0线源自金属3 p到1 s的跃迁，它们已被用作析氧络合物中Mn上电荷和自旋状态的指示剂（OEC;图1）。[7，8]高能量
Ligands play critical roles during the catalytic reactions in inorganic systems and in metalloproteins through bond formation and breaking, protonation and deprotonation, and electron and spin delocalization. There are well-defined element-specific spectroscopic handles, such as X-ray spectroscopy and EPR spectroscopy, to follow the chemistry of metal catalytic sites. However, directly probing particular ligand atoms such as C, N, and O, especially in a large protein matrix, is challenging owing to their abundance in the protein. FTIR and Raman spectroscopy and ligand-sensitive EPR spectroscopy techniques such as ENDOR and ESEEM have been applied to study metal–ligand interactions. X-ray absorption spectroscopy (XAS) can also probe the ligand environment; its element-specificity allows us to focus only on the catalytic metal site, and EXAFS and XANES provide metal–ligand distances, coordination numbers, and symmetry of ligand environments. However, the information is limited, because it is impossible to distinguish among ligand elements with similar atomic number (ie C, N, and O). As an alternative and a more direct method to probe the specific metal–ligand chemistry in the protein matrix, we investigated the application of X-ray emission spectroscopy (XES). Using this technique, we have identified the oxo bridging ligands of the Mn4Ca complex of photosystem II (PS II), a multisubunit membrane protein that catalyzes the water-oxidizing reaction in photosynthesis.[1] The catalytic mechanism has been studied intensively by manganese XAS.[2] The fundamental challenge, however, is to learn how the water molecules are ligated to the Mn4Ca cluster and how OÀO bond formation occurs before the evolution of O2.[3–5] This implies that it is necessary to monitor the chemistry of the oxygen ligands to understand the mechanism.XES, which is a complementary method to XAS, has the potential to directly probe ligation modes.[6] Among the several emission lines, Kβ1, 3 and Kβо lines originate from the metal 3p to 1s transition, and they have been used as an indicator of the charge and spin states on Mn in the oxygenevolving complex (OEC; Figure1).[7, 8] The higher-energy
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影响因子：
4.6
作者：
Ruettinger, WF;Ho, DM;Dismukes, GC
通讯作者：
Dismukes, GC
影响因子：
15
作者：
Smolentsev, Grigory;Soldatov, Alexander V.;Glatzel, Pieter
通讯作者：
Glatzel, Pieter
影响因子：
4.4
作者：
Bergmann, U;Bendix, J;Cramer, SP
通讯作者：
Cramer, SP
影响因子：
2.8
作者：
Bergmann, U;Horne, CR;Cramer, SP
通讯作者：
Cramer, SP
影响因子：
3.5
作者：
BERTHOLD, DA;BABCOCK, GT;YOCUM, CF
通讯作者：
YOCUM, CF