Preferential Binding of Thioflavin T to AT-Rich DNA: White Light Emission through Intramolecular Förster Resonance Energy Transfer.

Herein we report the effect of different nucleobase pair compositions on the association-induced fluorescence enhancement property of Thioflavin T (ThT), upon binding with 20 base pair long double-stranded DNA (dsDNA). Analysis of binding and decay constants along with the association (Kass) and dissociation (Kdiss) rate constants obtained from the fluctuation in the fluorescence intensity of ThT after binding with different DNA revealed selective affinity of ThT toward AT-rich dsDNA. Molecular docking also substantiates the experimental results. We also observed that addition of orange-emitting ethidium bromide (EtBr) to cyan-emitting ThT-DNA complexes leads to bright white light emission (WLE) through Förster resonance energy transfer. Additionally, the emission of white light is far greater in the case of intra-DNA strands. Besides endorsing the binding insights of ThT to AT-rich dsDNA, the present investigations open a new perspective for realizing promising WLE from two biomarkers without labeling the DNA.