Biophysical insights into the interaction of two enantiomers of Ru(II) complex [Ru(bpy)(2)(7-CH3-dppz)](2+) with the RNA poly(U-A*U) triplex

摘要

To determine the factors affecting the stabilization of RNA triple-stranded structure by chiral Ru(II) polypyridyl complexes, a new pair of enantiomers, increment -[Ru(bpy)(2)(7-CH3-dppz)](2+)( increment -1; bpy = 2,2 '-bipyridine, 7-CH3-dppz = 7-methyl-dipyrido[3,2-a,2 ',3 '-c]phenazine) and Lambda-[Ru(bpy)(2)(7-CH3-dppz)](2+)(Lambda-1), have been synthesized and characterized in this work. Binding properties of the two enantiomers with the RNA poly(U-A*U) triplex (where "-" denotes the Watson - Crick base pairing and "*" denotes the Hoogsteen base pairing) have been studied by spectroscopy and hydrodynamics methods. Under the conditions used in this study, changes in absorption spectra of the two enantiomers are not very different from each other when bound to the triplex, although the binding affinity of increment -1is higher than that of Lambda-1. Fluorescence titrations and viscosity experiments give convincing evidence for a true intercalative binding of enantiomers with the triplex. However, melting experiments indicated that the two enantiomers selectively stabilized the triplex. The enantiomer increment -1stabilize the template duplex and third-strand of the triplex, while it's more effective for stabilization of the template duplex. In stark contrast to increment Delta-1, Lambda-1 stabilizes the triplex without any effect on the third-strand stabilization, suggesting this one extremely prefers to stabilize the template duplex rather than third-strand. Besides, the triplex stabilization effect of increment Delta-1 is more marked in comparison with that of Lambda-1. The obtained results suggest that substituent effects and chiralities of Ru(II) polypyridyl complexes play important roles in the triplex stabilization.