Excitation energy-transfer processes between two trimers in C-phycocyanin hexamer from the cyanobacterium Anabaena variabilis.: Investigation by group theory and time-resolved fluorescence spectroscopy

We have employed group theory and picosecond time-resolved fluorescence isotropy and anisotropy spectroscopy methods to explore the excitation transfers within an isolated C-phycocyanin (C-PC) hexamer (alpha beta)(6)L-PC(RC)27, situated at the end of the rod proximal to the core of the pycobilisome (PBS) in the cyanobacterium Anabaena variabilis. The group-theory results imply that excitation energy transfer between two trimers occurs between the lowest exciton level of each trimer. The excitation energy-transfer process might occur at a rate of 10-20 ps, and it may be described by an exciton hopping-like Forster transfer mechanism. Dynamic components of 45-50 ps are assigned to the excitation transfer from beta(155)-PCB chromophores to the exciton states of dimers. which consist of two neighbouring monomers of the same trimer in an isolated C-PC hexamer. (C)1999 Elsevier Science S.A. All rights reserved.