Yano Junko, Yachandra Vittal K
Melvin Calvin Laboratory, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Photosynth Res. 2007 Jun;92(3):289-303. doi: 10.1007/s11120-007-9153-5. Epub 2007 Apr 12.
A detailed electronic structure of the Mn4Ca cluster is required before two key questions for understanding the mechanism of photosynthetic water oxidation can be addressed. They are whether all four oxidizing equivalents necessary to oxidize water to O2 accumulate on the four Mn ions of the oxygen-evolving complex, or do some ligand-centered oxidations take place before the formation and release of O2 during the S3 --> [S4] --> S0 transition, and what are the oxidation state assignments for the Mn during S-state advancement. X-ray absorption and emission spectroscopy of Mn, including the newly introduced resonant inelastic X-ray scattering spectroscopy have been used to address these questions. The present state of understanding of the electronic structure and oxidation state changes of the Mn4Ca cluster in all the S-states, particularly in the S2 to S3 transition, derived from these techniques is described in this review.
在解决理解光合水氧化机制的两个关键问题之前，需要了解锰钙簇（Mn4Ca）的详细电子结构。这两个问题是：将水氧化为氧气所需的所有四个氧化当量是否都积累在析氧复合物的四个锰离子上，或者在S3→[S4]→S0转变过程中，在氧气形成和释放之前是否发生了一些以配体为中心的氧化反应；以及在S态推进过程中锰的氧化态是如何确定的。锰的X射线吸收和发射光谱，包括新引入的共振非弹性X射线散射光谱，已被用于解决这些问题。本综述描述了通过这些技术得出的对所有S态，特别是S2到S3转变过程中Mn4Ca簇的电子结构和氧化态变化的当前理解状态。
