Osnabrück 2002 – wissenschaftliches Programm
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SYBP: Biophotonik
SYBP 4: Postersitzung
SYBP 4.13: Poster
Donnerstag, 7. März 2002, 17:45–20:00, Schloss
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
Photosynthesis involves the absorption of light and the rapid transfer of energy towards the photochemical reaction centre. The great difficulty to determine the various parameters that play a role in the description of the electronic structure of light-harvesting complexes is the fact that the optical absorption lines are inhomogeneously broadened as a result of heterogeneity in the ensemble of absorbing pigments.
We have circumvented this problem by studying individual LH2 complexes from the photosynthetic purple bacterium Rhodospirillum molischianum at 1.4 K. These complexes consists of 24 BChl a molecules arranged in C8 symmetry in two concentric rings containing eight and sixteen pigments, respectively. 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 as well as sudden changes in the spectral position of individual lines. Rotating the polarisation of the incident laser light allows us to determine the mutual orientations of the involved transition-dipole moments.