Binding properties of chiral ruthenium(II) complexes Lambda- and Delta-[Ru(bpy)(2)dppz-11-CO2Me](2+) toward the triplex RNA poly(U)center dot poly(A)*poly(U)

摘要

Two chiral ruthenium(II) complexes containing ligand dppz-CO2Me (dppz-11-CO2Me = dipyrido[3,2-alpha,2',3'-c]phenazine-11-carboxylic acid methyl ester), Delta-[Ru(bpy)2dppz-11-CO2Me](2+) (bpy = 2,2'-bipyridine; Delta-1) and Lambda-[Ru(bPY)(2)dppz-11-CO2Me](2+) (Lambda-1), were synthesized and characterized. The binding of the two enantiomers with the triplex RNA poly(U)center dot poly(A)*poly(U) was carried out by various biophysical techniques. Analysis of the absorption and fluorescence features indicates that the binding strengths of the two enantiomers toward the triplex RNA differ only slightly from each other. The total increase in viscosity and shape of the curves for the triplex RNA with Lambda-1 is similar to that with Delta-1, suggesting the binding modes of two enantiomers with the triplex RNA are intercalation. Thermal melting measurements indicate that the stabilization effects clearly depended on the concentrations of Lambda-1 and Delta-1. However, the third -strand stabilizing effect of Delta-1 dramatically differs from that of Lambda-1 when they interact with the chiral environment of the RNA triple at pH = 7.0 and [Na+] = 35 mM. Combined with the CD (CD = circular dichroism) variations of the triplex RNA with either Lambda-1 or Delta-1, the reason for their different triplex stabilization effects may originate from the two enantiomers through different orientations intercalating into nucleobases of the triplex. In addition, effects of higher ionic strengths on the triplex stabilization in the absence and presence of the two enantiomers have also been studied. The results presented here may be useful for understanding the binding properties of the triplex RNA with small molecule, particularly chiral ruthenium(II) complexes.