Regensburg 2002 – wissenschaftliches Programm
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SYBM: Physik biologischer Materie
SYBM 202: Spectroscopy of single biomolecules
SYBM 202.2: Vortrag
Dienstag, 12. März 2002, 15:15–15:30, H37
Spectroscopy of the B800 Band of Individual Light Harvesting 2 (LH2) Complexes from Rhodospirillum molischianum. — •C. Hofmann1, M. Ketelaars2, M. Matsushita3, J. Schmidt3, H. Michel4, T.J. Aartsma2, and J. Köhler5 — 1Department of Physics and CeNS, University of Munich — 2Department of Biophysics, Leiden University — 3Centre for the Study of Excited States of Molecules, Leiden University — 4Department of Molecular Membrane Biology, MPI of Biophysics Frankfurt — 5Experimental Physics 4, University of Bayreuth
Pigment-protein complexes play an important role in light harvesting of bacterial photosynthesis, i.e. the absorption of sunlight and the rapid transfer of energy towards the reaction centre. In order to elucidate structure-function relationships of these systems detailed knowledge of the electronic structure of the complexes is inevitable. From x-ray crystallography it is known that the LH2 complex from Rs. molischianum consists of 24 BChl a molecules arranged in C8 symmetry in two concentric rings containing eight and sixteen pigments, respectively. We obtained the fluorescence-detected absorption spectra of individual complexes at 1.4 K which show spectra rich in details usually masked in ensemble experiments. For the BChl a molecules of the eight-ring (B800) several relatively narrow absorption lines are observed. We will present the dependence of the spectra on intensity and polarisation of the incident radiation. We could observe spectral diffusion and sudden changes in the spectral position of individual lines. Rotating the polarisation of the incident laser light allows us directly to determine the mutual orientations of the involved transition-dipole moments.