Intrinsic Turn-On Response of Thioflavin T in Complexes.

The fluorescence enhancement ("turn-on") response of the amyloid-sensing dye thioflavin T (ThT) is examined in vacuo, where solvent interactions are absent. Upon the complexation of ThT with a derivatized β-cyclodextrin, heptakis-[6-deoxy-6-(3-sulfanylpropanoic acid)]-β-cyclodextrin, turn-on responses in both the gas phase and solution phase were observed. In contrast, turn-on response was not detected when ThT was bound to gaseous cucurbit[7]uril or human telomeric DNA 22AG, whereas clear turn-on response occurs in solution. The observed difference in turn-on response in the gas phase emphasizes the key interplay between chromophore, host and solvent and demonstrates the utility of gas-phase spectroscopy to tease out the balance among intermolecular forces driving the behavior of important chromophores in solution.