Hexammineruthenium (III) chloride: a highly efficient promoter of the B-DNA to Z-DNA transition of poly-(dG-m 5dC)·poly(dG-m 5dC) and poly(dG-dC)·poly(dG-dC)

Abstract

The effects of Ru(NH 3) 6 3+ on the conformation of poly(dG-m 5dC)·poly(dG-M 5dC) and poly(dG-dC)·poly(dG-dC) were studied by circular dichroism (CD) spectroscopy. Ru(NH 3) 6 3+ at very low concentrations provokes the Z-DNA conformation in both polynucleotides. In the presence of 50 mM NaCl, the concentration of Ru(NH 3) 6 3+ at the midpoint of B to Z transition of poldy(dG-m 5dC)°poly(dG-m 5dC) is 4 μM compared to 5 μM for Co(NH 3) 6 3+. The half-lives of the B to Z transition of poly(dG-m 5dC)·poly(dG-m 5dC) in the presence of 10 μM Ru(NH 3) 6 3+ and Co(NHG 3) 6 3+ are at 23 and 30 min, respectively. The concentration of Ru(NH 3) 6 3+ at the midpoint of B to Z transition of poly(dG-dC)·poly(dG-dC) is 50 μM. These results demonstrate that Ru(NH 3) 6 3+ is a highly efficient trivalent cation for the induction of B to Z transition in poly(dG-m 5dC)·poly(dG-m 5dC) and poly(dG-dC)·poly(dG-dC). In contrast, Ru(NH 3) 6 3+ has no significant effect on the conformation of calf thymus DNA, poly(dA-dT)·poly(dA-dT) and poly(dA-dC)·poly(dG-dT).