光系统II电子结构在水裂解过程中的快速演化
Rapid Evolution of the Photosystem II Electronic Structure during Water Splitting
摘要：
光合水氧化是维持生物圈的基本过程。嵌入在光系统II蛋白环境中的Mn $_{4}$ Ca簇负责大气氧的产生。在这里，时间分辨X射线发射光谱（XES）被用来实时观察氧的形成过程。这些实验表明，氧的析出步骤，由三个连续的激光闪光，伴随着快速（50 $μ$ s内）的变化，锰K $β$ XES光谱。然而，没有氧化的Mn $_{4}$ Ca核心以上的所有Mn $^{\text{IV}}$状态被检测到之前O-O键的形成。提出了一种新的机制来解释光谱结果，该机制以S $_{3}$态中形成Mn $^{\text{IV}}$ = O为特征。该化学配方与S $_{3}$状态的独特反应性一致，并解释了以下S $_{3}$到S $_{0}$转变的促进作用，部分解决了与O-O键形成相关的动力学限制。在所提出的机制中，O-O键的形成先于最终（4 $^{\text{th}}$）电子从Mn $_{4}$ Ca团簇的转移，与实验一致。
英文摘要：
Photosynthetic water oxidation is a fundamental process that sustains the biosphere. A Mn$_{4}$Ca cluster embedded in the photosystem II protein environment is responsible for the production of atmospheric oxygen. Here, time-resolved x-ray emission spectroscopy (XES) was used to observe the process of oxygen formation in real time. These experiments reveal that the oxygen evolution step, initiated by three sequential laser flashes, is accompanied by rapid (within 50 $μ$s) changes to the Mn K$β$ XES spectrum. However, no oxidation of the Mn$_{4}$Ca core above the all Mn$^{\text{IV}}$ state was detected to precede O-O bond formation. A new mechanism featuring Mn$^{\text{IV}}$=O formation in the S$_{3}$ state is proposed to explain the spectroscopic results. This chemical formulation is consistent with the unique reactivity of the S$_{3}$ state and explains facilitation of the following S$_{3}$ to S$_{0}$ transition, resolving in part the kinetic limitations associated with O-O bond formation. In the proposed mechanism, O-O bond formation precedes transfer of the final (4$^{\text{th}}$) electron from the Mn$_{4}$Ca cluster, in agreement with experiment.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
