WHAT CAUSES THE CHANGES OF THIOFLAVIN T PHOTOPHYSICAL CHARACTERISTICS UPON ITS BINDING TO AMYLOID FIBRILS?
In this paper, we analyzed the existing hypotheses on the aggregation of the fluorescent probe thioflavin T (ThT) molecules in the free and bound to amyloid fibrils states. The ability of ThT to form excimers in an aqueous solution at a high dye concentration was shown experimentally. A comparative study of the photophysical characteristics of ThT in the monomeric and aggregated forms and the dye bound to lysozyme amyloid fibrils was carried out. The obtained results allowed to show the unreasonableness of the assumption that the change in the ThT photophysical characteristics upon incorporation into amyloid fibrils is due to aggregation of the dye molecules. It was confirmed a monomer model of ThT binding to amyloid fibrils and concluded that the increase in the ThT fluorescence quantum yield when the dye incorporated into fibrils is due only to its molecular rotor nature (by the restriction of the ThT fragments rotation relative one another due to the increase in the rigidity of its microenvironment).