Interaction of octahedral ruthenium(II) polypyridyl complex [Ru(bpy)2(PIP)]2 + with poly(U)·poly(A)*poly(U) triplex: Increasing third-strand stabilization of the triplex without affecting the stability of the duplex

Abstract

Triple-helical RNA are of interest because of possible biological roles as well as the potential therapeutic uses of these structures, while the stability of triplexes is usually weaker than that of the Watson–Crick base pairing duplex strand due to the electrostatic repulsion between three polyanionic strands. Therefore, how to increase the stability of the specific sequences of triplexes are of importance. In this paper the binding of a Ru(II) complex, [Ru(bpy)2(PIP)]2+ (bpy=2.2′-bipyridine, PIP=2-phenyl-1H-imidazo[4,5-f]- [1,10]-phenanthroline), with poly(U)·poly(A)*poly(U) triplex has been investigated by spectrophotometry, spectrofluorometry, viscosimetry and circular dichroism. The results suggest that [Ru(bpy)2(PIP)]2+ as a metallointercalator can stabilize poly(U)·poly(A)*poly(U) triplex (where · denotes the Watson–Crick base pairing and * denotes the Hoogsteen base pairing),while it stabilizes third-strand with no obvious effect on the duplex of poly(U)·poly(A), reflecting the binding of this complex with the triplex is favored by the Hoogsteen paired poly(U) third strand to a great extent.