FTIR Difference Spectrum of the Photooxidation of the Primary Electron Donor of Photosystem II

Abstract

In the isolated D1D2 reaction center (RC) of photosystem II, the primary electron donor (P680) is thought to consist of a weakly coupled dimer or multimer of chlorophyll α (Ch1) molecules [1]. Upon light absorption, charge separation occurs between P680 and a pheophytin α molecule (Phe). The radical pair P680⁺Phe− recombines to the ³P680 triplet state, which has been already characterized by FTIR difference spectroscopy [2; J. B. & E. N., unpublished]. Illumination of RCs in the presence of the electron acceptor silicomolybdate (SiMo), leads to the reversible photoaccumulation of P680⁺ [3–5]. Here, we report on a preliminary characterization of the P680⁺/P680 FTIR difference spectrum in D1D2 RCs.