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首页> 外文期刊>Chemistry: A European journal >A Structure-Consistent Mechanism for Dioxygen Formation in Photosystem II
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A Structure-Consistent Mechanism for Dioxygen Formation in Photosystem II

机译：光系统中双氧形成的结构一致机理

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摘要

In recent DFF studies a new mechanism for O-O bond formation at the oxygen evolving center (OEC) in photosystem II has been suggested. With the structure of the S-4 state required for that mechanism. the structures of the lower S states are investigated herein by adding protons and electrons. A model was used including the full amino acids for the ones ligating the OEC. and in which the backbone positions were held fixed from the X-ray structure. The only charged second-shell ligand Arg357 was also included. An optimized structure for the S, state was reached with a large similarity to one of those suggested by EXAFS. A full catalytic cycle was derived which can rationalize the structural relaxation in the S-2 to S-3 transition, and the fact that only all electron leaves in the transition before. Water is suggested to bind to the OEC in the S-2 to S-3 and S-4, to S-0 transitions. A new possibility for water exchange is suggested from the final energy diagram. The optimal O-O bond formation occurs between an oxygen radical and an oxo ligand. The alternative mechanism, where the oxygen radical reacts with an external water, has a barrier about 20 kcal mol(-1) higher.
机译：在最近的DFF研究中​​，已经提出了在光系统II中的氧演化中心（OEC）形成O-O键的新机制。具有该机制所需的S-4状态。本文通过添加质子和电子来研究低S态的结构。使用了一个模型，其中包括连接OEC的全部氨基酸。并且其中的骨干位置从X射线结构保持固定。还包括唯一带电的第二壳配体Arg357。达到了S，​​状态的优化结构，与EXAFS建议的结构有很大的相似性。得出了一个完整的催化循环，可以合理化S-2到S-3过渡中的结构弛豫，以及只有所有电子在过渡之前离开的事实。建议水在S-2到S-3和S-4到S-0的过渡中与OEC结合。从最终的能量图中提出了一种新的水交换可能性。最佳的O-O键形成发生在氧自由基和氧代配体之间。氧自由基与外部水反应的另一种机制具有更高约20 kcal mol（-1）的势垒。

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