Theory and Experiment in Photosynthetic Electron Transfer

Abstract

The recent determination of the crystallographic structure of a bacterial photosynthetic reaction center has provided an important framework for treating electron transfers in these systems. As in electron transfers in simpler systems, a knowledge of both the structure and the thermodynamics is needed for understanding the experimental results on reaction rates at the fundamental level. In this lecture we first describe the theory of simple electron transfer reaction rates, and then consider how the resulting interaction between theory and experiment may assist us in treating electron transfers in the photosynthetic reaction center. In the final portion of this talk we summarize a view of the current state of knowledge in this electron transfer complex, and some of the questions which remain. We include in our discussion the very recent and dramatic results of Zinth and coworkers on the role of the bacteriochlorophyll monomer at room temperature (2), presented also at this Congress. Ultimately, all of the evidence for the mechanism should fit. In bacterial photosynthesis we have not yet reached that state, but several recent developments have perhaps begun to simplify the picture, examined in this lecture.