Berlin 2005 – scientific programme

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MO: Molekülphysik

MO 12: Biomolecules I

MO 12.3: Talk

Friday, March 4, 2005, 14:45–15:00, HU 2091

Femtosecond Fluorescence Spectroscopy of Bacteriorhodopsin Features a Dynamic Stokes Shift — •Bernhard Schmidt, Constanze Sobotta, Björn Heinz, Stefan Laimgruber, Markus Braun, and Peter Gilch — Department für Physik, Ludwig-Maximilians-Universität München, Oettingenstr. 67, D-80538 München, Germany

Bacteriorhodopsin (BR) acts as a light driven proton pump which allows archea to benefit from solar energy. A crucial step in the photocycle of BR is the isomerisation of its retinal chromophore. By virtue of numerous femtosecond experiments there is now consensus on time scales involved, but the underlying molecular processes are still under debate. As time resolved fluorescence spectroscopy is particularly suitable to probe the primary dynamics in the excited state, we report such experiments relying on the Kerr technique. The resulting spectra feature a dynamic Stokes Shift occurring on a timescale of 0.2 ps, which is indicative for a fast re-arrangement on the reactive potential energy surface. In agreement with other experiments time constants of ≤ 0.15 ps and 0.45 ps for the decay of the fluorescence have been determined.