Challenges of observing O–O bond formation in the Mn4Ca cluster of photosystem II

IF 19.1 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Chem Pub Date : 2025-07-10 DOI:10.1016/j.chempr.2025.102448

Scott Jensen , Brendan T. Sullivan , Daniel A. Hartzler , Irina Kosheleva , Robert W. Henning , Allison Page , Yulia Pushkar

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Abstract

Photosystem II (PS II) sustains the biosphere by enabling oxygen evolution in the S₃-to-S₀ transition (duration ∼1–2 ms) of its catalytic cycle. Using time-resolved Mn K_β X-ray emission spectroscopy, we observed spectroscopic changes (which were unimpeded in D₂O buffer) consistent with a modified electronic structure as early as ∼50 μs in the transition. These changes are consistent with the reduction of the Mn centers at the ∼50–200 μs time window in H₂O and at ∼50–500 μs in D₂O, ahead of the reduction of the redox-active Tyr_Z^⋅+. These results indicate the multi-step nature of O–O bond formation and O₂ release by the oxygen-evolving complex (OEC), where an O–O bond is most likely formed prior to the final electron-transfer step. The D₂O-induced extension of up to ∼500 μs in the lifetime of the early transient state of a possible peroxo nature opens it up to further spectroscopic and structural analysis.

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光系统II中Mn4Ca簇O-O键形成观察的挑战

光系统II （PS II）通过在其催化循环的s3到s0过渡（持续时间~ 1-2 ms）中使氧析出来维持生物圈。利用时间分辨的Mn Kβ x射线发射光谱，我们观察到光谱变化（在D2O缓冲液中不受阻碍）早在跃迁过程中约50 μs就与修饰的电子结构一致。这些变化与Mn中心在H2O和D2O中分别在~ 50-200 μs和~ 50-500 μs时间窗口的还原一致，且还原活性的TyrZ⋅+的还原先于Mn中心的还原。这些结果表明，氧演化配合物（OEC）形成O-O键和释放O2的多步骤性质，其中O-O键最有可能在最后的电子转移步骤之前形成。在可能的过氧性质的早期瞬态寿命中，d20诱导的延长高达~ 500 μs，为进一步的光谱和结构分析开辟了道路。

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来源期刊

Chem Environmental Science-Environmental Chemistry

CiteScore

32.40

自引率

1.30%

发文量

281

期刊介绍： Chem, affiliated with Cell as its sister journal, serves as a platform for groundbreaking research and illustrates how fundamental inquiries in chemistry and its related fields can contribute to addressing future global challenges. It was established in 2016, and is currently edited by Robert Eagling.