Nonphotochemical hole burning of the native antenna complex of photosystem I (PSI-200)

Nonphotochemical hole burning is used to determine the frequencies and Franck-Condon factors for 41 chlorophyll a (Chla) and 15 Chlb intramolecular modes for PSI-200. The linear electron-vibration coupling for all modes is very weak with the maximum Franck-Condon factor observed being ∼0.04. No activity by modes with a frequency lower than 7sim;260 cm^-1 is observed. The linear electron-phonon coupling for protein modes of mean frequency 22 cm^-1 is stronger but can still be categorized as weak since the Huang-Rhys factor is 0.8. The experimental mode and phonon frequencies and Franck-Condon factors are used with multiphonon excitation transport theories to analyze the available temperature-dependent data on the kinetics of transport within the core antenna complex. The calculations indicate that it is the phonons (and not the intramolecular modes) that mediate excitation transport within the antenna and from the antenna to the reaction center. They indicate also that a subunit or cluster model for the antenna provides a more accurate picture than the regular array model for excitation transport.