Electric Field Modulation of the Fluorescence Lineshape for Photosynthetic Reaction Centers: A New Probe of the Primary Electron Transfer Mechanism

Abstract

The rate of an electron transfer reaction such as the initial charge separation step in the bacterial photosynthetic reaction center (RC) is expected to be sensitive to an applied electric field [1], The origin of this sensitivity can be seen by reference to Figure 1: assuming that the initial charge-separated state, generically called P⁺I⁻, has a dipole moment, the free energy change, ΔG°, for the initial ¹P → P⁺I⁻ step and consequently the rate for this reaction should depend on an externally applied electric field. The precise mapping of ΔG° into rate for this reaction is not known. Various models have been proposed for the dependence of this rate on ΔG° [1–3]. In most cases a strong dependence of the rate on electric field is predicted.