Distinguishing between Energy and Electron Transfer Processes in Photosystem Two Reaction Centres.

Abstract

The photosystem two (PS2) reaction centre (RC) undertakes both electron and energy transfer processes as part of its function. Distinguishing between these two processes is an essential pre-requisite for meaningful studies of the primary photochemistry of this complex. In the reaction centre (RC) of purple bacteria, the energy transfer processes are relatively simple, and result in the unidirectional transfer of excitation energy to the special pair in approx. 100fs. In contrast, in the PS2 RC of higher plants, extensive forward and backward energy transfer is expected due to the relatively small energy separation between the S1 states of the RC chlorins.