Hamburg 2009 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 65: Laseranwendungen: Lebenswissenschaften

Q 65.1: Talk

Friday, March 6, 2009, 14:00–14:15, VMP 8 HS

Photo-dynamics of Roseoflavin in Aqueous and Organic Solvents — •Peyman Zirak¹, Alfons Penzkofer¹, Tilo Mathes², and Peter Hegeman² — ¹Institut II - Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany — ²Institut für Biologie /Experimentelle Biophysik, Humboldt Universität zu Berlin, Invalidenstraße 42, D-10115 Berlin, Germany

Roseoflavin (8-dimethylamino-8-demethyl-D-riboflavin) in aqueous and organic solvents is studied by optical absorption spectroscopy, fluorescence spectroscopy, and fluorescence decay kinetics. A solvent polarity dependent absorption shift is observed. The fluorescence quantum yield is low and solvent dependent (e.g. 0.0005 in neutral water and 0.032 in benzene). The fluorescence decay shows a bi-exponential dependence (ps to sub-ps fast time constant, and 100 ps to a few ns slow time constant). The photo-dynamics is explained in terms of fast intra-molecular charge-transfer (diabatic electron transfer) from the dimethylamino electron donor group to the pteridin carbonyl electron acceptors followed by intra-molecular charge recombination. The fast fluorescence component is due to direct locally excited-state emission, and the slow fluorescence component is due to delayed locally excited state emission and charge transfer state emission.