Kinetics of energy transfer processes in C-phycocyanin complexes

Abstract

The antenna system of algae for photosynthesis is a functional entity composed of various phycobiliproteins and the linker polypeptides. Up to now, high-resolution crystal structure data have been available only for the isolated phycohiliproteins. To have an understanding of the functional connection between different phycobiliproteins, it is necessary to study the complexes composed of different phycobiliproteins. The energy transfer processes in C-phycocyanin complexes were studied through computer simulation because it is dificult to be studied by conventional experimental methods. The main pathways of energy flow and the dynamic property of the energy transfer were obtained. A fast transfer process between two neighboring disks was observed through analyzing the distribution curves of excitation energy over time. According to the definition of the time constants for energy transfer in time-resolved spectrum techniques, for a complex with three C-phycocyanin hexamer disks, a fluorescence-rising component with several picoseconds was obtained in disk 2 and 20 ps in disk 3 when the chromophores in disk 1 were excited by an ideal Δ pulsed laser beam. The results showed clearly that the energy transfer between the disks in an antenna rod was very fast and that energy transfer was fast and efficient in an intact antenna system of algae.