Targeting DNA abasic site by myricetin: Sequence-dependent ESIPT emission

Many efforts have been made for sequence-specific recognition of DNA by small molecules. In this study, abasic site (AP site) in a DNA duplex was found to be targeted by myricetin (Myr), one of the natural 3-hydroxyflavonols. Steady-state and transient-state fluorescence, FRET, and DNA melting experiments confirmed that the AP site binding of Myr favors an emission from its tautomer that is derived from excited-state intramolecular proton transfer (ESIPT) reaction between the 3-OH and 4-carbonyl moieties. The selective recognition of Myr is less dependent on the flanking bases of the AP site, although the ESIPT emission is more lighting up for the DNAs with cytosine and thymine opposite the AP site. Because Myr alone in aqueous solution is non-fluorescent, this selective lighting-up emission is advantageous for developing a practical sensor to target the DNA AP site with a weak fluorescence background. This selective recognition of the AP site by the lighting-up fluorescence response would find wide applications including efficiently evaluating DNA damage/repair and screening antitumor/antioxidation drugs.