Nuclear wavepacket motion producing a reversible charge separation in bacterial reaction centers

• Published in: FEBS letters 2000-01, Vol.466 (2), p.209-212
• Main Authors: Yakovlev, A.G., Shkuropatov, A.Y., Shuvalov, V.A.
• Format: Article
• Language: English
• Subjects: BA and HA, monomeric bacteriochlorophyll and bacteriopheophytin molecules, respectively, located in active branch A; Electron acceptor; Electron donor; Electron transfer; Electron Transport; ET, electron transfer; F, Franck–Condon factor; Kinetics; Light-Harvesting Protein Complexes; P, primary electron donor; Photosynthetic Reaction Center Complex Proteins - chemistry; Q, quinone; RC, reaction center; Reaction center; Rhodobacter sphaeroides - chemistry; Wavepacket; ΔA, light−dark absorbance changes
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(00)01081-4

The excitation of bacterial reaction centers (RCs) at 870 nm by 30 fs pulses induces the nuclear wavepacket motions on the potential energy surface of the primary electron donor excited state P*, which lead to the fs oscillations in stimulated emission from P* [M.H. Vos, M.R. Jones, C.N. Hunter, J. Breton, J.-C. Lambry and J.-L. Martin (1994) Biochemistry 33, 6750–6757] and in Q Y absorption band of the primary electron acceptor, bacteriochlorophyll monomer B A [A.M. Streltsov, S.I.E. Vulto, A.Y. Shkuropatov, A.J. Hoff, T.J. Aartsma and V.A. Shuvalov (1998) J. Phys. Chem. B 102, 7293–7298] with a set of fundamental frequencies in the range of 10–300 cm −1. We have found that in pheophytin-modified RCs, the fs oscillations with frequency around 130 cm −1 observed in the P*-stimulated emission as well as in the B A absorption band at 800 nm are accompanied by remarkable and reversible formation of the 1020 nm absorption band which is characteristic of the radical anion band of bacteriochlorophyll monomer B A −. These results are discussed in terms of a reversible electron transfer between P* and B A induced by a motion of the wavepacket near the intersection of potential energy surfaces of P* and P +B A −, when a maximal value of the Franck–Condon factor is created.