Herbert Treutlein, Klaus Schulten, Axel Brünger, Martin Karplus,
J. Deisenhofer, and H. Michel.
Chromophore-protein interactions and the function of the
photosynthetic reaction center: A molecular dynamics study.
Proceedings of the National Academy of Sciences, USA,
89:75-79, 1992.
TREU91
The coupling between electron transfer and protein structure and dynamics in the photosynthetic reaction center of em Rhodopseudomonas viridis is investigated. For this purpose molecular dynamics simulations of the essential portions (a segment of 5797 atoms) of this protein complex have been carried out. Electron transfer in the primary event is modeled by altering the charge distributions of the chromophores according to quantum chemical calculations. The simulations show (em i) that fluctuations of the protein matrix, which are coupled electrostatically to electron transfer, play an important role in controlling the electron transfer rates and (em ii) that the protein matrix stabilizes the separated electron pair state through rapid (200fs) and temperature-independent dielectric relaxation. The photosynthetic reaction center resembles a polar liquid in that the internal motions of the whole protein complex, rather than only those of specific side groups, contribute to em i and em ii. The solvent reorganization energy is about 4.5 kcal/mol. The simulations indicate that rather small structural rearrangements and changes in motional amplitudes accompany the primary electron transfer.
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