Department of Chemistry, School of Natural Sciences, The University of Manchester, Manchester M13 9PL, U.K.
J Am Chem Soc. 2020 Jun 10;142(23):10240-10243. doi: 10.1021/jacs.0c01351. Epub 2020 May 27.
The identity of a key intermediate in the S to S transition of nature's water-oxidizing complex (WOC) in Photosystem 2 is presented. Broken-symmetry density functional theory (BS-DFT) calculations and Heisenberg-Dirac-van Vleck (HDvV) spin ladder calculations show that an S state open cubane model of the WOC containing a μ-hydroxo O4 changes from an = / form to an = /, form upon deprotonation of W1. Combined with X-band electron paramagnetic resonance (EPR) spectral analysis, this indicates that the = 4.1 EPR signal corresponds to an = / form of the WOC with W1 present as a water ligand to Mn, while the = 4.8/4.9 form observed at high pH values corresponds to an = / form, with W1 as a hydroxo ligand. The latter is also likely to represent the form needed to progress to S in the functioning enzyme.
揭示了自然界水氧化复合物（WOC）在光系统 2 中 S 到 S 跃迁的关键中间物的身份。非对称密度泛函理论（BS-DFT）计算和海森堡-狄拉克-范维克（HDvV）自旋梯级计算表明，包含 μ-羟氧 O4 的 WOC 的 S 态开口立方烷模型在 W1 去质子化后从 = / 形式转变为 = / 形式。结合 X 波段电子顺磁共振（EPR）光谱分析，这表明 = 4.1 EPR 信号对应于 W1 作为 Mn 的水配体的 WOC 的 = / 形式，而在高 pH 值下观察到的 = 4.8/4.9 形式对应于 W1 作为羟氧配体的 = / 形式。后者也可能代表在功能酶中进行 S 所需的形式。
