Charge separation events in photosystem II during the S 2 to S 3 transition as revealed by EPR spectroscopy

2025/11/26 by Georgia Zahariou · 1 voice
Biochemistry, Genetics and Molecular Biology · Chemistry · #Metal-Catalyzed Oxygenation Mechanisms #Photosynthetic Processes and Mechanisms #Redox biology and oxidative stress

paper · doi:10.1002/1873-3468.70229

openalex publication_date 2025/11/26 · openalex created_date 2025/11/28 · openalex updated_date 2026/06/15

Abstract

Photosystem II (PSII) water oxidation includes proton and electron transfer pathways, occurring during the sequential S‐state transitions of Mn 4 CaO 6 . Here, we investigate the charge separation events during the S 2 to S 3 transition that take place via the S 2 TyrZ • intermediate, utilizing electron paramagnetic resonance (EPR) spectroscopy. The increasing number of cycles of S 2 TyrZ • formation and decay results in a gradual diminution of the S 2 TyrZ • signal intensity which is proportional to the amount of S 3 state. Our results point to the progressive accumulation of a different configuration of the donor side of PSII at the S 2 state that allows the Mn 4 CaO 6 to be oxidized. These results consolidate previous investigations supporting that, during the lifetime of the S 2 TyrZ • , a proton from Mn 4 CaO 6 is removed, prior to the advancement to the S 3 state.

Citations

• UN NOUVEAU MODELE DES CENTRES PHOTOCHIMIQUES DU SYSTEME II*
• COOPERATION OF CHARGES IN PHOTOSYNTHETIC O2 EVOLUTION–I. A LINEAR FOUR STEP MECHANISM
• Eight steps preceding O–O bond formation in oxygenic photosynthesis—A basic reaction cycle of the Photosystem II manganese complex

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