Electronic Structure of Manganese Cluster in Photosystem II Investigated by ESR

Abstract

Electronic structure of Manganese cluster in photosystem II was investigated by Electron Spin Resonance (ESR) spectroscopy. Spin projections on Mn ions in S₂ state manganese cluster were determined by Pulsed Electron-Electron Double Resonance (PELDOR). Protons surrounded manganese cluster were detected by Electron Nuclear Double Resonance (ENDOR). Based on obtained spin projections, ENDOR signals were assigned to the water molecules ligated to manganese cluster. PELDOR technique was applied to the determination of the high affinity Mn²⁺ site in apo-photosystem II, which is the key site of photo-activation process of manganese cluster.