Untangling the sequence of events during the S2 → S3 transition in photosystem II and implications for the water oxidation mechanism
Abstract
A new bridging oxygen ligand is incorporated between one of the Mn atoms and Ca in the Mn4Ca cluster during the transition from the one-photon induced S2 intermediate state to the two-photon induced S3 state in the catalytic water oxidation reaction in photosystem II. However, the sequence of events leading to this change is not known. Here we report an X-ray crystallography and spectroscopy study at room temperature using an X-ray free electron laser to collect a "molecular movie" of the structural and oxidation state change steps leading to the insertion of this new oxygen bridge, in the 50 µs to 200 ms time scales after photon absorption, which triggers the S2 → S3 state transition.
- Publication:
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Proceedings of the National Academy of Science
- Pub Date:
- June 2020
- DOI:
- Bibcode:
- 2020PNAS..11712624I