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BP: Fachverband Biologische Physik

BP 16: Poster Session I

BP 16.4: Poster

Dienstag, 27. März 2007, 17:00–19:30, Poster D

Energy Transfer between Photosynthetic Pigment-Protein Complexes in Model Membrane Systems — •Tobias Pflock¹, Manuela Dezi², Giovanni Venturoli², Jürgen Köhler¹, and Silke Oellerich¹ — ¹Experimentalphysik IV, Universität Bayreuth, D-95447 Bayreuth — ²Dept. of Biology, University of Bologna, Italy

The photosynthetic unit (PSU) of purple bacteria represents a well known model system in photosynthesis research. It mainly consists of protein complexes, namely LH2 and LH1-RC, which contain photoactive pigment molecules harvesting solar light. The ring-shaped complexes are embedded in lipid membranes to form functional units that very efficiently transfer the excitation energy to the reaction center (RC). Therefore, the supramolecular organisation of the PSU within the biological membrane plays a significant role, and it is of particular interest to understand how the involved lipids contribute to the spatial arrangement of the membrane proteins.

In order to address this question systematically, we chose to reconstitute proteins into large unilamellar vesicles (LUV). This allows us to control the membrane lipid composition as well as the lipid-protein ratio. Selective excitation of the pigments embedded in LH2 rings by a pulsed laser makes it possible to determine the transfer efficiency to LH1-RC units directly via fluorescence lifetime measurements. Using a streak camera system we studied the fluorescence decay of reconstituted pigment-protein complexes to characterize excitation energy transfer from LH2 to LH1-RC complexes.