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+

Two new chiral ruthenium (II) complexes, A-[Ru (bpy)2 (10-OH-dppz)]2+ (A-1; bpy = 2,2MODIFIER LETTER PRIME-bipyridine, 10-OH-dppz = 10-hydroxyl-dipyrido [3,2-a:2 ',3 '-c]phenazine) and A-[Ru (bpy)2 (10-OH-dppz)]2+ (A-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 A-1 toward the triplex is somewhat smaller than that of enantiomer A-1, which is further supported by viscosity experiments. Viscosity experiments showed that although the two enantiomers were intercalated to the triplex, the A-enantiomer was a better intercalator than the A-enantiomer. Furthermore, thermal denaturation experiments demonstrate that although the two enantiomers can significantly increase the triplex stabilization, unlike enantiomer A-1, enantiomer A-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 A-1 was significantly stronger than that by A-1. The obtained results indicate that the binding ability of enantiomers A-1 and A-1 to the triplex is dependent on the chirality of enantiomers.