Synthesis, characterization and DNA binding studies of two Ru(II) complexes containing guanidinium ligands

Two new Ru(II) complexes containing guanidinium groups have been synthesized, characterized and analyzed according to their interactions with different G-quadruplexes and duplex DNA. A FRET assay and a competitive FRET assay showed that both complexes promote the formation and stabilization of the human telomeric (h-telo) G-quadruplex and exhibit higher selectivity compared to promoters (such as c-myc, c-kit and bcl2) or duplex DNA. After binding to G-quadruplex, the two complexes have shown different DNA affinity and fluorescence enhancement. CD analyses further indicate that the two complexes display the ability to induce and stabilize the formation of antiparallel G-quadruplex structures in K + , Na + or ion-free buffers. The binding stoichiometry with h-telo was of the order of three ruthenium complexes per quadruplex.