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Recognition and regulation of G-quadruplex nucleic acid structures is an important goal for the development of chemical tools and medicinal agents. The addition of a bromo-substituent to the dipyridylphenazine (dppz) ligands in the photophysical "light switch", Ru(bpy)2 dppz(2+) , and the photochemical "light switch", Ru(bpy)2 dmdppz(2+) , creates compounds with increased selectivity for an intermolecular parallel G-quadruplex and the mixed-hybrid G-quadruplex, respectively. When Ru(bpy)2 dppz-Br(2+) and Ru(bpy)2 dmdppz-Br(2+) are incubated with the G-quadruplexes, they have a stabilizing effect on the DNA structures. Activation of Ru(bpy)2 dmdppz-Br(2+) with light results in covalent adduct formation with the DNA. These complexes demonstrate that subtle chemical modifications of Ru(II) complexes can alter G-quadruplex selectivity, and could be useful for the rational design of in vivo G-quadruplex probes.
Wachter et al. (Thu,) studied this question.