Comparison of Energetics of P*QA → P+Q A - and P*QB → P+Q B - Charge Separation by Detection of Delayed Fluorescence of the Bacteriochlorophyll Dimer in Reaction Centers of Rb. sphaeroides

Abstract

Flash absorbed by the reaction center (RC) initiates electron transfer from the excited bacteriochlorophyll dimer (P*) to the adjacent cofactors (bacteriopheophytin I, primary quinone QA and secondary quinone Q8) (Fig. 1). The free energy levels of the charge separated states P+Q A - and P+Q B - relative to that of the P*Q excited state can be directly determined from delayed luminescence (DL) of P* (1–3) and related to results obtained from proton binding measurements (2–4). Open image in new window Figure 1 Origin of the leakage-type delayed fluorescence and the free energy levels of the redox states P+QH- and PQAQ, relative to that of the excited (P*Q) state of the RC with approximate numerical values of the rate constants. Note that there is no direct recombination from charge separated state P+Q B - .