Pulsed ENDOR study of spin-correlated radical pair in photosystem I

Abstract

Spin-correlated radical pair constitutes the short-lived intermediate P700⁺A₁^- of photosystem I. In the applied magnetic filed, the radical pair has four eigenstates, singlet S> and triplet T1> T0> T-1>states. Initially, most of the spins are poplulated on S> and T0> states by CIDEP ,mechanism. Therefore, the intense ESR signals can be observed on the transitions between T0> and T1/-1>. We have detected some ENDOR transitions in the P700⁺A₁^- radical pair by applying RF irradiation. The ENDOR signals are superimposed on ENDOR signals of each radical. Detailed analysis is now in progress.