Time-Resolved Fluorescence Spectroscopy of Phycoerythrin, Phycocyanin, and Allophycocyanin Crystals

Reza Ranjbar Choubeha, Ravi R. Sonanib,c, Datta Madamwarb, Bruno Robertc, Paul C. Struikd, Arjen Badera,e, Herbert van Amerongena,e
aLaboratory of Biophysics, Wageningen University, Wageningen, The Netherlands; bSardar Patel University, Gujarat, India; cInstitute of Biology and Technology of Saclay, Gif-sur-Yvette, France; dCenter for Crop System Analysis, Wageningen University, Wageningen, The Netherlands; eMicroSpectroscopy Center, Wageningen University, Wageningen, The Netherlands

Phycobilisomes are light-harvesting antennas used by cyanobacteria and red algae. Three major light harvesting components of phycobilisomes from cyanobacterium Phormidium sp. A09DM are phycoerythrin (PE), phycocyanin (PC), and allophycocyanin (APC). When PE is excited, it transfers the excitation energy to PC and from there it goes to APC. It is debated whether the excitation energy transfer (EET) in and between PE, PC, and APC is of excitonic nature or of Förster resonance energy transfer type.

Understanding EET in these three pigment-protein complexes helps to unravel the underlying mechanisms which make EET efficient and to identify general principles shared with other photosynthetic components. We have performed picosecond fluorescence time-resolved spectroscopy on hexameric crystals of PE and PC, and trimeric crystals of APC in order to characterize EET within these complexes and the results will be presented.