9405248 Holten The reaction center (RC) of photosynthetic organisms is the membrane bound pigment-protein complex within which light energy is converted into chemical energy via a series of fast and highly specific electron transfer reactions. The overall process separates charge across the RC (and hence across the membrane) with an essentially unity quantum yield. The ultimate goal of this research is to arrive at a comprehensive understanding of this process at a molecular level. To this end, transient absorption spectroscopic measurements spanning the femtosecond to millisecond timescales as well as other spectroscopic techniques will be used to directly identify and study the intermediate states of charge separation and the rates of their formation and decay. These studies will be carried out on both wild-type RCs and a wide variety of mutant RCs in which one or more amino acids are changed using the techniques of molecular biology. %%% This research has broad implications that transcend photosynthesis reasch. The investigations will impact on the general understanding of electron transfer. The RC is in many respects a mini-laboratory for the investigation of this fundamental process in view of knowledge of the structure of the RC and the ability to manipulate and investigate the charge separation events in detail. The studies will also address the role of the protein in the energy conversion process, and thus will impact on the important area of how the interactions between amino acids and the imbedded cofactors influence biological events. This work additionally forms the foundation for understanding and developing efficient mechanisms for the capture and storage of solar energy. Hence, this research is important not only for understanding a natural process essential for life on earth, but also for gaining further knowledge in areas of broad importance in biologyand chemistry. ***
