Femtosecond Energy Transfer Processes in C-Phycocyanin and Allophycocyanin Trimers

Allophycocyanin and C-Phycocyanin are photosynthetic antenna pigments of the light-harvesting complexes (phycobilisomes) of blue greem bacteria and red algae. Important questions under investigations are related to transfer of excitation energy between nearby chromophores in aggregates (mainly trimers) of C-PC and APC. One has, for instance, to discuss different models for the energy transfer including Förster and excitoic mechanisms. APC monomer contains two chromophores, namely α84 and β84 ones. The optical spectrum of the APC monomer has the maximum at 620 nm. In contrast to this, the spectrum of APC trimer has a sharp peak at 650 nm and a shoulder about 620 nm. In contrast to APC, C-phycocyanin monomer contains three chromophores, α84, β84 and β155, and absorption spectrum of the C-PC trimer with maximum near 620 nm shows close resemblance to that of the C-PC monomers.