Department of Physics, School of Science and Technology, Meiji University, 1-1-1 Higashimita, Tama-ku, 214, Kawasaki, Kanagawa, Japan.
Photosynth Res. 1993 Jan;38(3):331-9. doi: 10.1007/BF00046758.
A set of Mn K-edge XANES spectra due to the redox states S0-S3 of the OEC were determined by constructing a highly-sensitive X-ray detection system for use with physiologically native PS II membranes capable of cycling under a series of saturating laser-flashes. The spectra showed almost parallel upshifts with relatively high K-edge half-height energies given by 6550.9±0.2 eV, 6551.7±0.2 eV, 6552.5±0.2 eV and 6553.6±0.2 eV for the S0, S1, S2 and S3 states, respectively. The successive difference spectra between S0 and S1, S1 and S2, and S2 and S3 states were found to exhibit a similar peak around 6552-6553 eV, indicating that one Mn(III) ion or its direct ligand is univalently oxidized upon each individual S-state transition from S0 to S3. The present data, together with other observations of EPR and pre-edge XANES spectroscopy, suggest that the oxidation state of the Mn cluster undergoes a periodic change; S0: Mn(III,III,III,IV) → S1: Mn(III,IV,III,IV) → S2: Mn(III,IV,IV,IV) → S3: Mn(IV,IV,IV,IV) or Mn(III,IV,IV,IV)·L(+) with L being a direct ligand of a Mn(III) ion.
一组 Mn K 边 XANES 光谱归因于 OEC 的氧化还原态 S0-S3，通过构建一个高灵敏度的 X 射线检测系统来实现，该系统可用于在一系列饱和激光闪烁下能够循环的生理天然 PS II 膜。光谱显示出几乎平行的上移，相对较高的 K 边半高能量分别为 6550.9±0.2 eV、6551.7±0.2 eV、6552.5±0.2 eV 和 6553.6±0.2 eV，分别对应于 S0、S1、S2 和 S3 态。在 S0 和 S1、S1 和 S2 以及 S2 和 S3 状态之间的连续差光谱中发现，在 6552-6553 eV 左右出现了一个类似的峰，表明在每个单独的 S 态从 S0 到 S3 的跃迁中，一个 Mn(III)离子或其直接配体被单价氧化。目前的数据，连同其他 EPR 和预边 XANES 光谱学的观察结果，表明 Mn 簇的氧化态经历周期性变化；S0：Mn(III,III,III,IV)→S1：Mn(III,IV,III,IV)→S2：Mn(III,IV,IV,IV)→S3：Mn(IV,IV,IV,IV)或 Mn(III,IV,IV,IV)·L(+)，其中 L 是 Mn(III)离子的直接配体。
