ИСТИНА

Primary electron transfer reactions in the bacterial reaction center (BRC) are difficult for theoretical explication: the reaction kinetics, being almost unalterable over a wide range of temperature and free energy changes, revealed oscillatory features observed initially by Shuvalov at al.1. Here the reaction mechanism was studied by molecular dynamics (MD) and analyzed within a phenomenological Langevin approach. The spectral function of polarization around the bacteriochlorophyll special pair PL/PM and the dielectric response upon the formation of PL+/PM− dipole within the special pair were calculated. The system response was approximated by a set of Langevin oscillators, the respective frequencies, friction and energy coupling coefficients were determined. The protein dynamics around PL and PM was determined to be highly asymmetric. The polarization around PL was described vastly by a single Debye mode with relaxation time of 80 fs and the amplitude of 130 mV; the protein response around PM could be largely described by two oscillatory modes with frequencies of ~90 and ~150 cm-1 and the total amplitude of 50 mV. The revealed polarization dynamics is in agreement with the oscillatory kinetics observed by Shuvalov et al. and could rationalize the known properties of BRC charge separation.