Polarization Measurements on Single Pigment-Protein Complexes

Abstract

Individual antenna complexes from different photosynthetic units have been investigated by single molecule spectroscopy. In such energy transfer systems the polarization of the fluorescence emission gives valuable information about the nature of the emitting state, which is not readily available with other methods like fluorescence excitation or emission spectroscopy. The peripheral antenna light harvesting complex from purple bacterium Rhodopseudomonas Acidophila shows predominantly linear polarized fluorescence emission at low temperature, whereas at room temperature the fluorescence is randomly polarized. This is attributed to the fact, that at low temperature in the fluorescence emitting state the excitation energy is localized mainly on 4‐5 chromophores. Analysis of the fluorescence emission of single peripheral antenna complexes of green plants indicate that for trimers of this species more than one Chlorophyll is responsible for the final fluorescence emission, which points towards a weak intermonomer coupling in the complex.

Parameters of the Protein Energy Landscapes of Several Light-Harvesting Complexes Probed via Spectral Hole Growth Kinetics Measurements

“…Second, to the best of our knowledge no low-temperature single complex data has ever been presented for CP43 and CP29 complexes. While some low-temperature singlecomplex data is available for LHCII 50,51,60,61 , these papers do not focus on spectral diffusion or barrier distribution parameters. Once respective single complex data becomes available, it could be verified against our SHB-based parameters.…”

Investigation of molecular dimers by ensemble and single molecule spectroscopy

“…Recently, various kinds of multichromophoric assemblies like conjugated polymer molecules [7], light-harvesting pigments [8][9][10][11], donor-acceptor substituted biopolymers [12,13] or dendrimers carrying different numbers of chromophores [14,15] have been studied by single molecule spectroscopy. A strong motivation for these experiments relates to the fact that electronic interactions can then be studied without averaging over the properties of an intrinsically inhomogeneous ensemble.…”