Oligopyridine-ruthenium(II)-amino acid conjugates: synthesis, characterization, DNA binding properties and interactions with the oligonucleotide duplex d(5 '-CGCGCG-3 ')(2)
Diastereomeric oligopyridine-ruthenium(II)-amino acid conjugated complexes of the general formulas Lambda- and Delta-[Ru(bpy)(2)(4,4'(CO2Y)(2)-bpy)](2+), where Y = L-AlaCONH(2), L-LysCONH(2), L-HisCONH(2), L-TyrCONH(2)), were synthesized and characterized. Their binding properties with ct-DNA and the oligonucleotide duplex d(5'CGCGCG-3')(2), by means of circular dichroism (CD), NMR spectroscopy and DNA thermal denaturation (T-m) curves were studied. CD and T-m data indicate that all diastereomeric complexes bind to the DNA major groove, Delta-diastereomers in a similar manner, while Lambda-diastereomers in dependence of the nature of the amino acid. NMR studies of d(5'CGCGCG-3')(2), and the complexes Delta-1, Delta-2, Lambda-1 and Lambda-2 indicate that Delta-1 and Delta-2 were bound having the ancillary bpy ligands towards the DNA groove, while the corresponding Lambda-1 and Lambda-2 were orientated in a similar way, facing the ligand 4,4'(CO2Y)(2)bpy towards the DNA major groove. Photoinduced DNA cleavage was observed in all cases studied, which take place through singlet oxygen production. Delta-4 and Lambda-4 show the lower photoinduced cleavage yield, probably because the singlet oxygen (O-1(2)) oxidizes not only the DNA phosporodiesteric bonds but the tyrosine's phenolic OH bond as well.