Abstract

During the last decade, the molecular background of the primary electron transfer (ET) in photosynthetic reaction centers (RC) has been the theme of numerous papers /1-4/. The unexpected fast reaction rate, the large distance between the electron donor (the special pair P) and the electron accepting bacteriopheophytin H_A, the role of the intermediary monomeric bacteriochlorophyll B_A, non-exponential decay kinetics, the speed up of the reaction at low temperatures and oscillations found in transient absorption experiments stimulated many discussions. In the meantime part of these questions have been answered: e. g. it has been shown that the ET-reaction at room temperature follows non-adiabatic ET-theory and that the monomeric intermediary BChl B_A is a real, but short-lived electron carrier /4/. Remaining important questions concern the energetics of the intermediate states, the heterogeneities in reaction dynamics and the possibility of adiabatic or coherent ET at low temperatures.

© 1996 Optical Society of America