Elastic Vibrations in the Photosynthetic Bacterial Reaction Center Coupled to the Primary Charge Separation: Implications from Molecular Dynamics Simulations and Stochastic Langevin Approach

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• 作者：Georgy E. Milanovsky ; Vladimir A. Shuvalov ; Alexey Yu. Semenov ; Dmitry A. Cherepanov
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：October 29, 2015
• 年：2015
• 卷：119
• 期：43
• 页码：13656-13667
• 全文大小：532K
• ISSN：1520-5207

文摘

Primary electron transfer reactions in the bacterial reaction center are difficult for theoretical explication: the reaction kinetics, almost unalterable over a wide range of temperature and free energy changes, revealed oscillatory features observed initially by Shuvalov and coauthors (1997, 2002). Here the reaction mechanism was studied by molecular dynamics and analyzed within a phenomenological Langevin approach. The spectral function of polarization around the bacteriochlorophyll special pair P_LP_M and the dielectric response upon the formation of P_Lp>+p>P_Mp>鈥?/sup> dipole within the special pair were calculated. The system response was approximated by Langevin oscillators; the respective frequencies, friction, and energy coupling coefficients were determined. The protein dynamics around P_L and P_M were distinctly asymmetric. The polarization around P_L included slow modes with the frequency 30鈥?0 cmp>鈥?p> and the total amplitude of 130 mV. Two main low-frequency modes of protein response around P_M had frequencies of 95 and 155 cmp>鈥?p> and the total amplitude of 30 mV. In addition, a slowly damping mode with the frequency of 118 cmp>鈥?p> and the damping time >1.1 ps was coupled to the formation of P_Lp>+p>P_Mp>鈥?/sup> dipole. It was attributed to elastic vibrations of 伪-helices in the vicinity of P_LP_M. The proposed trapping of P excitation energy in the form of the elastic vibrations can rationalize the observed properties of the primary electron transfer reactions, namely, the unusual temperature and 螖G dependences, the oscillating phenomena in kinetics, and the asymmetry of the charge separation reactions.