Regensburg 2007 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: POSTER: Biological Systems + New Materials
CPP 20.4: Poster
Wednesday, March 28, 2007, 16:00–18:30, Poster B
The electronic structure of core complexes from Rps. palustris — •Thomas Prem1, Martin Richter1, Jürgen Baier1, Silke Oellerich1, Francesco Francia2,3, Giovanni Venturoli2, Dieter Oesterhelt3, June Southall4, Richard Cogdell4, and Jürgen Köhler1 — 1Experimental Physics IV and BIMF, University of Bayreuth — 2Department of Biology, University of Bolonga and INFM, Italy — 3Department for Membrane Biochemistry, MPI for Biochemistry, Martinsried — 4Division of Biochemistry and Molecular Biology, University of Glasgow, United Kingdom
The primary reactions of purple bacterial photosynthesis occur within two pigment-protein complexes, the core RC-LH1 complex and the peripheral LH2 complexes. In the RC the reduction of a uniquinone (UQ) to ubiquinol (UQH2) takes place. In order to make contact with the cytochrome b/c1 complex as part of the cyclic electron pathway, the UQH2 has to leave the RC. Hence, either the LH1 ring is not complete, i.e. there is a gap, or the LH1 structure is inherently flexible enough to allow UQH2 to diffuse through it. A recent rather low resolution X-ray crystal structure of the RC-LH1 core complex from Rps. palustris showed the presence of a gap in the LH1 ring. This presence, though functionally critical, has become very controversial. We recorded single-molecule fluorescence-excitation spectra for individual RC-LH1 complexes of Rps. palustris and describe how the presence of a narrow spectral feature at the low-energy end of the spectrum unequivocally establishes the presence of a gap in the electronic structure consistent with the presence of the physical gap.