Time-Resolved Fluorescence Spectroscopy Study of Energy Transfer Dynamics in Phycobilisomes from Cyanobacteria Thermosynechococcus vulcanus NIES 2134 and Synechocystis sp. PCC 6803

Abstract

As the largest light-harvesting complex in cyanobacteria, phycobilisomes (PBSs) show high efficiency and a high rate of energy transfer, owing to an elegant antenna-like assembly. To understand the structural influence on the dynamic process of the energy transfer in PBSs, two cyanobacterium species Thermosynechococcus vulcanus NIES 2134 (T. 2134) and Synechocystis sp. PCC 6803 (S. 6803) with different rod–core-linked assemblies were chosen for this study. The dynamic process of the energy transfer in both PBSs was investigated through time-resolved fluorescence spectroscopy (TRFS) with a time resolution of sub-picosecond. Via the fluorescence decay curves deconvolution, the pathways and related rates of the excitation energy transfer (EET) were determined. Three time components, i.e., 10, 80, and 1250 ps, were identified in the EET in the PBSs of T. 2134 and three, i.e., 9, 115, and 1680 ps, in the EET in the PBSs of S. 6803. In addition, a comparison of the dynamic process of the energy transfer between the two cyanobacteria revealed how the PBS assembly affects the energy transfer in PBSs. The findings will provide insight into future time-resolved crystallography.