Energy Transfer in Trimeric C-phycocyanin Studied by Picosecond Fluorescence Kinetics

The excited state kinetics of trimeric C-phycocyanin from Masrigocladus /arnirzosu.c. has been measured as a function of the emission and excitation wavelength by the single-photon timing technique with picosecond resolution and simultaneous data analysis. A last decay componcnt o f 22 ps (C-phycocyanin with linker peptides) and 36 ps (C-phycocyanin lacking linker peptides) is attributed to efficient energy transfer from sensitizing to fluorcscing chromophores. At long dctcction wavelengths the fast decay components are found to turn into a rise t a m . This finding further corroborates thc concept o f intramolecular energy transfer. Previous reports on the conformational heterogeneity of the chromophores and/or proteins in C-phycocyanin are confirmcd. Our da ta also provide indications for the importancc of the uncoloured linker peptides for this hctcrogeneity.