We are examing the photobleaching and transfer dynamics in single assemblies of the LH complexes and the ??-dipeptides that can be reversibly extracted from them. Each LH2 contains eighteen bacteriochlorophylls (B850) and nine collectors (B800). The fluorescence lifetimes, polarization, correlation times and bleaching kinetics are being studied under a variety of conditions. The primary goals include measurements of long time scale protein dynamics. Polarization experiments have revealed conformational dynamics associated with excitonic migration in the nonameric LH2 assembly. Furthermore, they have indicated that the single assemblies are not circular electronically as would be expected from X-ray diffraction studies.
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