Binding and stabilizations effects of RNA triplex poly(U*A-U) by enantiomers of ruthenium(II) polypyridyl complex [Ru(bpy)2(10-OH-dppz)]2+

Abstract

Two new chiral ruthenium (II) complexes, Δ-[Ru (bpy)2 (10-OH-dppz)]2+ (Δ-1; bpy = 2,2ʹ-bipyridine, 10-OH-dppz = 10-hydroxyl-dipyrido [3,2-a:2′,3′-c]phenazine) and Λ-[Ru (bpy)2 (10-OH-dppz)]2+ (Λ-1), have been synthesized and characterized in this work. The binding properties of the two enantiomers with an RNA triplex poly (U*A-U) [in text, dash (−) denotes the Watson-Crick base pairing and the asterisk (*) denotes the Hoogsteen base pairing] have been studied. Analysis of the absorption and fluorescence spectra suggest that the binding constant of enantiomer Λ-1 toward the triplex is somewhat smaller than that of enantiomer Δ-1, which is further supported by viscosity experiments. Viscosity experiments showed that although the two enantiomers were intercalated to the triplex, the Δ-enantiomer was a better intercalator than the Λ-enantiomer. Furthermore, thermal denaturation experiments demonstrate that although the two enantiomers can significantly increase the triplex stabilization, unlike enantiomer Λ-1, enantiomer Δ-1 stabilizes the Watson-Crick base-paired duplex and the Hoogsteen base-paired third strand of the triplex with obvious selectivity. In addition, the triplex stabilization by enantiomer Δ-1 was significantly stronger than that by Λ-1. The obtained results indicate that the binding ability of enantiomers Δ-1 and Λ-1 to the triplex is dependent on the chirality of enantiomers.