Excitation energy transfer in carotenoid-chlorophyll protein complexes probed by femtosecond fluorescence decays

An energy transfer pathway in a carotenoid-chlorophyll a protein complex of dinoflagellates was studied by the femtosecond up-conversion method. The energy levels of the S2 state of peridinin and their lifetime were essentially identical in methanol and in the complex. The S1 lifetime of peridinin in solvents was more than 30-fold longer than in the complex. These results account for an observed transfer efficiency (higher than 85%) and indicate that an energy transfer occurs between the S1 states of peridinin and chlorophyll a after a rapid internal conversion. This pathway is unique in photosynthetic organisms.