(393c) Modeling Excitation Energy Transfer In Photosynthetic Systems: Application to Peridinin-Chlorophyll-Protein Complex In Dinoflagellates

Photosynthetic light-harvesting complexes (LHC) have evolved over many millions of years to become extremely efficient at funneling excitation energy into their respective reaction centers. If these funneling processes are better understood, we can apply this knowledge to building an efficient bio-solar photovoltaic cell. Peridinin-chlorophyll-protein (PCP) complex is a LHC containing twenty-four peridinin and six chlorophyll-a pigment molecules, as shown by its x-ray crystallography structure.¹ We are studying the excitation energy transfer rates throughout the PCP complex using time-dependent density functional theory (TD-DFT) to calculate the pigment excited states, and Förster theory to calculate the transfer rates between pigment excited states. Since Förster theory does not take into account delocalized excitation states, we will extend our study to other quantum dynamics theories that allow delocalization. The excitation transfer pathway in PCP has been shown experimentally to go from the S2 to S1 state in peridinin, and from the S1 state in peridinin to the Qy state in chlorophyll-a.² Researchers have also been successful in reconstituting different species of chlorophyll molecules into the PCP complex array to tune the transfer efficiencies.³ Our goal is to validate the transfer efficiencies of these known complexes using the computational methods outlined above and to extend these methods to study unknown LHC systems.

[1] Hofmann, E., et. al. Science 272, 1788-1791 (1996).

[2] Damjanovic, A., Ritz, T. and Schulten, K. Biophysical Journal 79, 1695-1705 (2000).

[3] Polivka, T., et. al. Photosynthesis Research 86, 217-227 (2005).