The theory of Forster-type migration between clusters of strongly interacting molecules: application to light-harvesting complexes of purple bacteria

Abstract

Excitation dynamics in the light-harvesting core antenna of purple bacteria was studied theoretically using a model of excitation delocalization over the circular aggregate of strongly interacting bacteriochlorophyll molecules (‘DCA model’) (V.I. Novoderzhkin and A.P. Razjivin, FEBS Lett. 330 (1993) 5). Energy transfer from the core antenna complex to the reaction center (RC) and between core antenna complexes was treated as a Forster-type process. The assumption of the DCA model for the core antenna offers an explanation of the experimental data on the excitation trapping by RCs (60 ps antenna excitation decay; quasi-irreversible trapping). The rate of excitation migration between neighboring antenna core complexes is well suited to the realization of the ‘lake model’. The advantages of the proposed model as compared with other models are discussed.