Regensburg 2007 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: POSTER: Biological Systems + New Materials
CPP 20.3: Poster
Mittwoch, 28. März 2007, 16:00–18:30, Poster B
Protein Dynamics in the Light of Single-Molecule Spectroscopy — •Jürgen Baier1, Martin Richter1, Silke Oellerich1, Richard Cogdell2, and Jürgen Köhler1 — 1Experimental Physics IV and BIMF, University of Bayreuth — 2Division of Biochemistry and Molecular Biology, University of Glasgow, United Kingdom
Proteins are supramolecular machines that perform a variety of tasks in living organisms. However, a protein is not a rigid structure and due to the relatively weak interactions that stabilise its 3-dimensional structure the lowest energy state of a protein is not unique. The potential energy hypersurface features a multitude of barriers and is commonly described by a rugged energy landscape where each minimum represents a different conformational substate. Since conformational fluctuations of the protein are equivalent to rearrangements of its atoms, chromophores embedded in the protein experience those changes as fluctuations in the local interactions. As a consequence the pigments react on conformational changes of the protein with changes of their electronic transition energies. Here we focus on the B800 BChl a molecules of the peripheral light-harvesting complex (LH2) from photosynthetic purple bacteria as local probes to study the conformational dynamics. We have recorded long sequences of fluorescence-excitation spectra from individual LH2 complexes and performed a statistical analysis of the spectral fluctuations of the B800 absorptions. The results are compared with predictions of the standard TLS model for spectral diffusion in glasses. We find a fundamental difference between the relaxation behaviour of our test protein and glasses.