A luminescence probe for c-myc G-quadruplex by a triphenylamine-appended ruthenium complex

Due to the essential roles of G-quadruplex in biological processes, the development of G-quadruplex luminescent probe is becoming more and more important for further understanding of the functions of G-quadruplex in biology. We herein reported that a ruthenium complex containing triphenylamine group exhibited "off-on" emission behavior after binding to G-quadruplex in the presence of luminescence quencher [Fe (CN6)](4-). The Ru-Fe system consists of a mixture of [Ru (phen)2(TPAD)]2+, where TPAD = N-4-(1H-imidazo [4,5-f] [1,10]phenanthroline-2-yl phenyl)-N-phenyl-benzenamine and [Fe (CN6)](4-), which showed luminescent selectivity toward parallel G-quadruplex (c-myc). The detection limit was 159 nM for c-myc. The ligand TPAD bearing nonplanar triphenylamine group and steric hindrance led to different DNA affinities toward various DNA structures. Luminescence experiments, CD spectra, G4-FID, FRET (fluorescence resonance energy transfer) measurements, and molecular docking results indicated that different DNA affinities and binding modes of the complex toward various DNA structures result in the luminescence selectivity.