Effect of substituents on the binding of Ru(II) polypyridyl complexes [Ru(bpy)2L]2+ (L = pnpip and mnpip) to poly(U-A•U) triplex

Abstract

Two ruthenium(Ⅱ) polypyridyl complexes as triple-helical RNA binders, [Ru(bpy)2pnpip](PF6)2 (Ru1, bpy = 2,2′-bipyridine, pnpip = 2-(4′-nitrophenyl)imidazo[4,5-f] [1,10]phenanthroline) and [Ru(bpy)2mnpip](PF6)2 (Ru2, mnpip = 2-(3-methyl-4-nitropnenyl)imidazo[4,5-f] [1,10] phenanthroline)), were synthesized and characterized in this work. The binding behaviors of complexes Ru1 and Ru2 with the RNA triplex poly(U-A•U) were studied by various biophysical techniques. The obtained results indicate that although the two complexes bind to the triplex in an intercalative mode, the binding affinity of Ru1 with the triplex is stronger than that of Ru2. Furthermore, Ru1 destabilized the template duplex, while Ru2 did not affect the stabilization of the duplex. The obtained results will advance our knowledge on the binding of Ru(Ⅱ) complexes with RNA triplex.