Ruthenium nucleic acids interactions

Heavier metal ions and metal complexes can find sites on nitrogen atoms of the nucleic acid bases. Examples are the platinum complex cisplatin and the DNA-cleaving antibiotic neocarzinostatin (Box 5-B). Can metals interact with the n electrons of stacked DNA bases A surprising result has been reported for intercalating complexes of ruthenium (Ru) and rhodium (Rh). Apparent transfer of electrons between Ru (II) and Rh (III) over distances in excess of 4.0 nm, presumably through the stacked bases, has been observed,181 as has electron transfer from other ions.181a Stacked bases are apparently semiconductors.182... 

Chen et al. recently reported the stable ruthenium-oxo-oxalato cluster Na7[Ru4(p3-0)4(C204)g] (2) (Fig. lc) as a particularly potent inhibitor of HIV-1 reverse transcriptase (RT) with an IC50 value of 1.9 nM [17], Apparently, the polyanionic cluster mimics poly anionic nucleic acid in its binding to HIV-1 RT through electrostatic interactions. The cluster shows promising anti-HIV-1 activity without being cytotoxic. In contrast to many polyoxometallates, this cluster has been demonstrated to be stable under physiological conditions. 

Tris(phenanthroline) complexes of ruthenium(II), cobalt(III), and rhodium(III) are octahedral, substitutionally inert complexes, and as a result of this coordina-tive saturation the complexes bind to double-helical DNA through a mixture of noncovalent interactions. Tris(phenanthroline) metal complexes bind to the double helix both by intercalation in the major groove and through hydrophobic association in the minor groove. " " Intercalation and minor groove-binding are, in fact, the two most common modes of noncovalent association of small molecules with nucleic acids. In addition, as with other small molecules, a nonspecific electrostatic interaction between the cationic complexes and the DNA polyanion serves to stabilize association. Overall binding of the tris(phenanthroline) complexes to DNA is moderate (log K = 4)." ... 

---