High Fluorescence Anisotropy of Thioflavin T in Aqueous Solution Resulting from Its Molecular Rotor Nature

Document Type


Publication Date


Digital Object Identifier (DOI)



Thioflavin T (ThT) is widely used to study amyloid fibrils while its properties are still debated in the literature. By steady-state and femtosecond time-resolved fluorescence we showed that, unlike small sized rigid molecules, the fluorescence anisotropy value of the free ThT in aqueous solutions is very high, close to the limiting value. This is determined by the molecular rotor nature of ThT, where the direction of the ThT transition dipole moment S0 → S1* is not changed either by the internal rotation of the ThT benzothiazole and aminobenzene rings relative to each other in the excited state, because the axis of this rotation coincides with the direction of the transition dipole moment, or by the rotation of the ThT molecule as a whole, because the rate of this process is 3 orders of magnitude smaller than the rate of the internal rotation which leads to the fluorescence quenching. Consequently, ThT fluorescence anisotropy cannot be directly used to study amyloid fibrils formation, as it was proposed by some authors.

Was this content written or created while at USF?


Citation / Publisher Attribution

American Chemical Society, v. 88, issue 1, p. 718-724