Hannover 2010 – scientific programme

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MO: Fachverband Molekülphysik

MO 7: Poster: Femtosecond Spectroscopy

MO 7.9: Poster

Tuesday, March 9, 2010, 16:00–18:30, Lichthof

Comparison of wave-packet dynamics in Bacteriorhodopsin and all-trans Retinal Protonated Schiff-Bases using Degenerate Four-Wave-Mixing — •Jan Philip Kraack^{1, 2}, Tiago Buckup¹, and Marcus Motzkus^1,2 — ¹Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany — ²Physikalische Chemie, Philipps-Universität, D-35043 Marburg, Germany

A prominent example for a light-harvesting system that converts light into chemical energy is Bacteriorhodopsin (bR) containing the all-trans retinal chromophore. Photon-absorption triggers a sub-picosecond, position-selective isomerization in protein-environment with a high quantum yield (0.65). This is contrasted by a slower (several picoseconds), unselective and inefficient isomerization of isolated all-trans retinal protonated Schiff-base (RPSB) in solution. This selectivity enhancement and acceleration effect of the protein environment has been a question of interest for a long time. We studied population and vibrational coherence dynamics on the sub-20 fs timescale using Degenerate Four-Wave-Mixing (DFWM) in order to clarify differences and analogies in the respective relaxation dynamics. We present detailed investigations on ground-state vibrational coherence dynamics and discuss the origin of excited state wave packet dynamics. Due to initial relaxation (<300 fs) and wave packet dynamics, we discuss the applicability of the 2-State-Two-Mode-Model [1], generally assumed to describe the relaxation dynamics of retinal-chromophores.

[1] González-Luque et al., PNAS 97, 2000, 9379