Optical Spectroscopy of Photosynthetic Complexes: Focus on Low-Temperature Protein Dynamics

To perform photosynthesis, plants, algae and bacteria possess well organized and closely coupled photosynthetic pigment-protein complexes. The information on energy transfer processes and protein dynamics contained in the narrow zero-phonon lines at low temperatures is hidden under the inhomogeneous broadening. Thus, it is difficult to analyze the spectroscopic properties of these complexes in sufficient detail by conventional spectroscopy methods. In this context, high resolution spectroscopy techniques such as Spectral Hole Burning, Fluorescence Line Narrowing and Single Molecule/Single Complex Spectroscopy are powerful tools designed to overcome the inhomogeneous broadening difficulty. This thesis focuses mainly on the low-temperature protein dynamics of several photosynthetic protein complexes (LH2, CP43, CP29 and LHCII). The hole growth kinetics and the shape of the anti-hole due to the non-photochemical spectral hole burning have been explored, and interpreted within the framework of theoretical models describing spectral diffusion due to conformational changes between nearly identical substates on a multi-tier protein energy landscapes.