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

Abstract 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 (αβ) 6 PC L 27 RC , 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 β 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.