Isobe Hiroshi, Shoji Mitsuo, Shen Jian-Ren, Yamaguchi Kizashi
Photosynthesis Research Center, Graduate School of Natural Science and Technology, Okayama University , Okayama 700-8530, Japan.
The Institute of Scientific and Industrial Research, Osaka University , Ibaraki, Osaka 567-0047, Japan.
J Phys Chem B. 2015 Oct 29;119(43):13922-33. doi: 10.1021/acs.jpcb.5b05740. Epub 2015 Oct 6.
We have studied the early phase of the S2 → S3 transition in the oxygen-evolving complex (OEC) of photosystem II using the hybrid density functional theory with a quantum mechanical model composed of 338-341 atoms. Special attention is given to the vital role of water molecules in the vicinity of the Mn4CaO5 core. Our results demonstrate how important the dynamic behavior of surrounding water molecules is in mediating critical chemical transformations such as binding and deprotonation of substrates and hydration of the catalytic site and identify a strong coupling of water-chain relocation near the redox-active tyrosine residue Tyr161 (TyrZ) with oxidation of the Mn4CaO5 cluster by TyrZ(•+). The oxidation reaction is further promoted when the catalytic site is more solvated by water. These results indicate the importance of surrounding water molecules in biological catalysts as they ultimately lead to effective catalytic function and/or favorable electron-transfer dynamics.
我们使用由338 - 341个原子组成的量子力学模型的杂化密度泛函理论，研究了光系统II放氧复合体（OEC）中S2→S3转变的早期阶段。特别关注了Mn4CaO5核心附近水分子的重要作用。我们的结果表明，周围水分子的动态行为在介导关键化学转化（如底物的结合和去质子化以及催化位点的水合作用）中是多么重要，并确定了氧化还原活性酪氨酸残基Tyr161（TyrZ）附近水链重排与TyrZ(•+)对Mn4CaO5簇的氧化之间的强耦合。当催化位点被水更好地溶剂化时，氧化反应会进一步促进。这些结果表明周围水分子在生物催化剂中的重要性，因为它们最终导致有效的催化功能和/或有利的电子转移动力学。
