Ultrafast Torsional Dynamics of Protein Binding Dye Thioflavin-T in Nanoconfined Water Pool

Photophysical properties and ultrafast excited state torsional dynamics of the protein binding dye, Thioflavin-T, have been investigated in a nanoconfined water pool of reverse micelles using both steady-state fluorescence and the femtosecond fluorescence upconversion technique. It is seen that due to the confined environment in the reverse micelle, the fluorescence yield of Thioflavin-T is dramatically enhanced approximately 250-fold as compared to that in bulk water. The fluorescence yield decreases nonlinearly with the increase in the water pool size of the reverse micelles. Fluorescence lifetime of Thioflavin-T is also seen to decrease sharply with an increase in the water pool size. The results have been rationalized on the basis of the effect of confinement on the ultrafast torsional motion in the Thioflavin-T. The rate constants for the torsional motion in Thioflavin-T molecule in confined water pool have been estimated.