München 2004 – wissenschaftliches Programm
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MO: Molekülphysik
MO 20: Schwingung und Rotation
MO 20.2: Vortrag
Freitag, 26. März 2004, 11:15–11:30, HS 355
Direct observation of Tiers in the Energy Landscape of a Chromoprotein: a Single-Molecule study — •Clemens Hofmann1, Martin Richter1, Thijs J. Aartsma2, Hartmut Michel3, and Jürgen Köhler1 — 1Experimental Physics IV, University of Bayreuth — 2Department of Biophysics, Leiden University — 3Department of Molecular Membrane Biology, MPI of Biophysics, Frankfurt
Pigment-protein complexes play an important role in light-harvesting of bacterial photosynthesis. From x-ray crystallography it is known that the light-harvesting 2 complex (LH2) from Rhodospirillum molischianum consists of 24 BChl a molecules arranged in C8 symmetry in two concentric rings containing eight and sixteen pigments, respectively. The electronically excited states of the eight-ring (B800) are mainly localised on individual BChl a molecules due to the weak coupling between the chromophores. A sensitive tool to monitor structural fluctuations of the protein backbone in the local environment of the chromophore is provided by recording the changes of the spectral positions of the pigment absorptions as a function of time. The data provide information about the organisation of the energy landscape of the protein in distinct tiers that can be characterised by an average barrier height. In addition, a clear correlation for the transition rates between those states and the energy separation of the levels is uncovered.
[1] Clemens Hofmann, Thijs J. Aartsma, Hartmut Michel, Jürgen Köhler, PNAS 100 15534-15538 (2003).
[2] Clemens Hofmann, Thijs J. Aartsma, Hartmut Michel, Jürgen Köhler New J. Phys. (in press).