Dinuclear Ruthenium(II) Complexes That Induce and Stabilise G-Quadruplex DNA

A series of dinuclear ruthenium(II) complexes were synthesised, and the complexes were determined to be new highly selective compounds for binding to telomeric G-quadruplex DNA. The interactions of these complexes with telomeric G-quadruplex DNA were studied by using circular dichroism (CD) spectroscopy, fluorescence resonance energy transfer (FRET) melting assays, isothermal titration calorimetry (ITC) and molecular modelling. The results showed that the complexes 1, 2 and 4 induced and stabilised the formation of antiparallel G-quadruplexes of telomeric DNA in the absence of salt or in the presence of 100 mm K+-containing buffer. Furthermore, complexes 1 and 2 strongly bind to and effectively stabilise the telomeric G-quadruplex structure and have significant selectivity for G-quadruplex over duplex DNA. In comparison, complex 3 had a much lesser effect on the G-quadruplex, suggesting that possession of a suitably sized plane for good pi-pi stacking with the G-quadruplets is essential for the interaction of the dinuclear ruthenium(II) complexes with the G-quadruplex. Moreover, telomerase inhibition by the four complexes and their cellular effects were studied, and complex 1 was determined to be the most promising inhibitor of both telomerase and HeLa cell proliferation.