Mainz 2017 – scientific programme

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MO: Fachverband Molekülphysik

MO 8: Fast Intramolecular Dynamics

MO 8.2: Talk

Tuesday, March 7, 2017, 15:00–15:15, N 25

Time-Resolved Spectroscopy of the Molecular Rotor Thioflavin T and its Building Blocks — •Bastian Geissler, Philipp Gerschel, Anna Lisa Semrau, and Patrick Nuernberger — Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum

Thioflavin T (ThT) is a benzothiazole salt linked to N,N-dimethylaniline. ThT is widely used as a marker for biophysical studies on the misfolding and aggregation of proteins. The spectroscopic properties of ThT depend on the freely rotatable bond between the benzothiazole and the aniline moieties. The associated rotation is the main (non-radiative) depopulation channel of the excited state, which has a lifetime well below 10 ps [1,2]. The fluorescence behavior of ThT exhibits a pronounced dependence on the excitation wavelength, attributed to the pre-rotation angle of the ground-state molecule [3].

We perform time-resolved spectroscopy via fluorescence upconversion, TCSPC and transient absorption for ThT and its building blocks. Depending on the excitation wavelength, fluorescence and excited-state dynamics drastically change, shifting from ps to ns. A comparison of ThT and benzothiazole confirms that for near-UV excitation, the ThT dynamics solely originate from a pre-rotated subensemble for which the two building blocks are spectroscopically independent and no excited-state depopulation through rotation occurs. Hence, our studies provide a time-domain corroboration of the pre-rotation model [3].
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