TCB Publications - Abstract

Dong Xu and Klaus Schulten. Multi-mode coupling of protein motion to electron transfer in the photosynthetic reaction center: Spin-boson theory based on a classical molecular dynamics simulation. In J. Breton and A. Vermeglio, editors, The Photosynthetic Bacterial Reaction Center: II. Structure, Spectroscopy and Dynamics, NATO Science Series A: Life Sciences, pp. 301-312. Plenum Press, New York, 1992.

XU92 We present a quantum mechanical description (spin-boson model) for electron transfer rates in the photosynthetic reaction center of Rh. viridis which assumes for the protein nuclear motion a broad distribution of vibrational modes rather than a few discrete modes. We demonstrate that linear coupling of electron transfer to such modes is in agreement with molecular dynamics simulations. We establish that the muli-mode coupling between electron transfer and protein motion can be described in surprisingly simple terms and requires as input only that one monitors the fluctuations of the so-called energy gap function $\Delta$ E (t), i.e., the energy required for a virtual transfer of the electron. The amplitude and the relaxation time of the associated correlation function are the essential parameters which determine electron transfer rates in the framework of the spin-boson model. We present the temperature and redox energy dependence of these rates which are found in agreement with observations and also with Marcus theory at high temperature, even though the latter assumes coupling to a single mode.

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