Excitonic Structure and Energy Transfer in Photosynthetic Pigment Protein Complexes and Their Assemblies
The research presented in this dissertation focuses on understanding how the spatial and energetic organization of pigment molecules within photosynthetic assemblies create efficient, natural light harvesting machines. In the first chapter we briefly describe photosynthetic light harvesting and explain the basic features of third-order spectroscopy and time-resolved fluorescence measurements used in this dissertation to characterize the relationship between the protein-bound pigments and their light harvesting processes. In chapter two, we start studying photosynthesis at the length scale of a single pigment-protein complex (PPC) and introduce a novel third-order frequency generation technique that is very sensitive to the excitonic structure of a PPCs. This technique is applied to a model pigment binding protein, the Fenna-Matthews-Olson (FMO) complex. In the third chapter, we propose a new approach to extracting information from optical, third-order measurements by combining chirplet transforms and shaped excitation pulses to glean information usually buried in the wings of the 2D electronic spectrum. Finally, in the fourth chapter, we consider longer length scale assemblies and treat photosystem II (PSII) supercomplexes which are composed of many individual PPCs. Using information gathered on isolated PPCs, we construct the first structure-based model of energy transfer in PSII supercomplexes to study the principles of light harvesting in functional photosynthetic machinery.