Excitation energy transfer mechanism in C-phycocyanin hexamer

Excitation energy transfer processes and mechanism in C-PC hexamer have been studied in detail by picosecond time-resolved fluorescencs isotropic and anisotropic spectroscopy methods. The experimental results show that there are two types of principal channels, with large probability or amplitude, for linking two trimers via mm and ss energy transfer pathways, the energy-transfer time constants of them are about 20 and 10 ps, respectively. Indeed, there exists the evidence for energy-transfer channels of sf steps in the same monomer and three ff steps in the same trimer of the C-PC hexamer unit, with small probability or amplitude, and the time constants of them might be ca. 50 and 45 ps separately. Also, the present results show that the hexamer possesses an optimal structure for energy-transfer and for the first time confirm that the dominant energy-transfer processes except those between 1m2f, 2m3f and 3m1f and so on, in isolated C-PC hexamer, could be described by F*irster dipole-dipole resonance mechanism.