A dinuclear ruthenium(II) complex as an inducer and potential luminescent switch-on probe for G-quadruplex DNA

Abstract

Given that recognition and regulation of G-quadruplex nucleic acid structures is an important goal for the development of chemical tools and medicinal agents, a dinuclear ruthenium complex [Ru2(bpy)4(bip-phenol)](ClO4)4 {bpy = 2,2′-bipyridine, bip-phenol = 2,4-bis(1H-imidazo[4,5-f] [1,10] phenanthroline-2-yl)phenol} has been synthesized and characterized, and its interactions with telomeric G-quadruplex DNA have been explored by photophysical and biophysical methods. This complex can induce and stabilize the formation of an antiparallel G-quadruplex of telomeric DNA in the absence of salt, or in the presence of K+/Na+-containing buffer. The complex binds strongly to the telomeric G-quadruplex, with a binding constant Kb > 106 and a 2:1 [complex]/[quadruplex] binding ratio. Fluorescence titrations revealed that the complex behaves as a promising photophysical “light switch” for G-quadruplex DNA, with 8.6- and 8.4-fold fluorescence enhancements in Na+ and K+ buffers, respectively.