Normal mode analysis of spectral density of FMO trimers: Intra- and intermonomer energy transfer
Sprache des Vortragstitels:
Englisch
Original Tagungtitel:
Quantum Dynamics and Spectroscopy of Functional Molecular Materials and Biological Photosystems
Sprache des Tagungstitel:
Englisch
Original Kurzfassung:
Intra- and intermonomer excitation energy transfer (EET) of the homotrimeric Fenna-Matthews-Olson (FMO) light-harvesting protein of green sulfur bacteria P. aestuarii is studied[1]. We employ the charge density coupling method for the calculation of local transition energies of the pigments combined with a normal mode analysis (NMA) of the protein for intermolecular contribution to the spectral density of the exciton-vibrational coupling. The high-frequency intrapigment part of the spectral density is extracted from fluorescence line-narrowing spectra.Correlations in site energy fluctuations across the whole FMO trimer are found at low vibrational frequencies, however, EET is not influenced by these correlations. We find the main contributions to the intramonomer EET originates from the high-frequency part of the spectral density, whereas intermonomer EET is dominated by the low-frequency intermolecular contributions to the spectral density. At room temperature, the intermonomer transfer in the FMO protein occurs on a 10 ps time scale, wheras intramonomer exciton equlibration is roughly two orders of magnitude faster. At cryogenic temperatures, intermonomer transfer limits the lifetimes of the lowest exciton band. The lifetimes are found to increase between 20 ps in the center of this band up to 100 ps towards lower energies, which is in very good agreement with the estimates from hole burning data [2].