Two structurally analogous ruthenium complexes as naked-eye and reversible molecular “light switch” for G-quadruplex DNA

A pair of symmetrical furyl based ruthenium(II) complexes ([Ru(phen)2dpq-df]2 + (1) and [Ru(bpy)2dpq-df]2 + (2) (phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine, dpq-df = dipyrido (3,2-a:2′,3′-c) quinoxaline-difuran) have been prepared and characterized. The binding properties of both complexes toward G-quadruplex DNA have been investigated by fluorescence spectroscopy, UV–Vis spectroscopy, circular dichroism (CD), fluorescence resonance energy transfer (FRET) melting assays and molecular docking studies. The experimental results indicated that both Ru-complexes exhibited a remarkable “light switch” effect in the presence of hybrid G-quadruplex DNA. Interestingly, the “light switch” can be repeated off and on through the successive addition of Cu2 + ions and EDTA, and all these behaviors can be observed even by the naked eyes. Moreover, FRET melting assay revealed that both complexes could be potential stabilizers for G-quadruplex architectures. The computational studies not only confirmed that the two complex molecules bound to one G-quadruplex DNA molecule, but also explained the “light switch” effect.

Graphical abstractThe reversible “light switch” behavior of two complexes toward G-quadruplex DNA and their binding mode were explained.Figure optionsDownload full-size imageDownload as PowerPoint slide