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SYND: Nonequilibrium Dynamics of Biomolecules

SYND 1: Sitzung 1

SYND 1.4: Invited Talk

Thursday, March 25, 2004, 15:30–16:00, HS 332

Ultrafast Conformational Dynamics in Cyclic Peptides — •Josef Wachtveitl — Goethe-Universität Frankfurt, Institut für Physikalische und Theoretische Chemie, Marie-Curie-Straße 11, 60439 Frankfurt am Main

Structural changes of peptides containing a modified azobenzene dye(AMPB) are studied with ultrafast spectroscopy. AMPB peptides represent a new class of molecules where the photoisomerizable dye azobenzene is linked to the peptide moiety via a flexible methylene spacer. The ultrafast reactions in the femtosecond to nanosecond time domain are investigated for the optical switch AMPB, a linear and cyclic octapeptide and a bicyclic octapeptide containing an additional disulfide bridge. These molecules with increasing conformational constraints, are studied for the cis to trans and the trans to cis photoreactions. For the cis to trans reaction the isomerization of the chromophore occurs fast in the 1 ps range, while it is slower (10 ps range) in the trans to cis reaction. In all peptides the structural changes of the chromophore lead to modifications in the peptide structure in the 10 ps to 1 ns time range. The results indicate that the chromophore AMPB acts simultaneously as a fast molecular switch and as a sensor for initial conformational dynamics in the peptide.