在光系统II中的S2到S3过渡期间,从氧进化复合体到电子受体氨酸的电子转移机制
Hiroyuki Tamura1,2, Keisuke Saito1,2, Hiroshi Ishikita1,2
1Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan.
ACS omega
|June 23, 2025
概括
光系II中的Mn4CaO5集群在S2到S3过渡期间从特定的水分子释放一个质子,影响电子转移. 这个步骤至关重要,并可能限制水氧化的速度.
科学领域:
- 生物化学 生物化学
- 光合作用研究研究 光合作用研究
- 量子化学 是一个量子化学.
背景情况:
- 光系II中的水氧化机制,由Mn4CaO5星团催化,仍然不完全理解.
- 在S2到S3过渡期间的质子合电子转移是争论的一个关键领域.
研究的目的:
- 调查Mn4CaO5集群中S2到S3过渡期间电子转移的详细机制.
- 阐明质子释放的作用及其在这种特定催化步骤中的起源.
主要方法:
- 使用量子力学/分子力学/极化连续模型 (QM/MM/PCM) 方法.
- 分析了Mn4CaO5集群内的静电相互作用,质子释放点和价值状态变化.
主要成果:
- 质子释放源于在Mn4的D1-Asp61附近的水分子 (W1),在Mn-IV形成OH-,而不是来自其他拟议的地点.
- 在Mn4-(IV) 中形成OH-会诱导从 (III,IV,IV,IV) 到 (IV,IV,IV,III) 的价值状态转换.
- 随后的水合并和TyrZ网络恢复促进了电子转移到TyrZ,在这个步骤中具有低电子合 (1-3 meV).
结论:
- 在S2到S3的过渡涉及特定的质子和电子转移,OH-形成在Mn4-(IV) 是一个关键的中间体.
- 这个步骤的低电子合表明它可能是整体水氧化循环的速度限制.
- 这些发现为光系统II的催化循环提供了关键的见解.
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