Synthesis, characterization and DNA binding properties of oligopyridine-ruthenium(II)-amino acid conjugates

The DNA-binding properties of a number of ruthenium oligopyridine complexes with conjugated amino acids having the general formulae [Ru(terpy)(4-COY-4′-Mebpy)(X)]n+, X = NO (n = 3), X = Cl (n = 1) and NO2 (n = 1) and Y = AlaCONH2 and TrpCONH2 are reported. The new complexes were spectroscopically characterized and their DNA-binding properties were studied by means of circular dichroism (CD), 23Na and 31P NMR spectroscopy. The results show that the chlorido complexes interact by coordination to the DNA bases with the conjugated amino acid able to provide an additional interaction with the DNA helix. In addition, electrostatic interactions between all studied complexes and the DNA polyanion were observed. The nitro complexes were found to be insignificant, affecting only the 31P NMR signal, probably due to changes in the hydration sphere of the DNA close to the phosphates.