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

Two ruthenium(Ⅱ) polypyridyl complexes as triple-helical RNA binders, [Ru(bpy) 2 pnpip](PF 6 ) 2 (Ru 1 , bpy = 2,2′-bipyridine, pnpip = 2-(4′-nitrophenyl)imidazo[4,5- f ] [1,10]phenanthroline) and [Ru(bpy) 2 mnpip](PF 6 ) 2 (Ru 2 , 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 Ru 1 and Ru 2 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 Ru 1 with the triplex is stronger than that of Ru 2 . Furthermore, Ru 1 destabilized the template duplex, while Ru 2 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. • Bpy = 2,2′-bipyridine, pnpip = 2-(4′-nitrophenyl)imidazo[4,5- f ] [1,10]phenanthroline. • Mnpip = 2-(3-methyl-4-nitropnenyl)imidazo[4,5- f ] [1,10] phenanthroline. • Complexes [Ru(bpy) 2 L] 2+ (L = pnpip and mnpip) were synthesized. • Binding properties of Ru 1 and Ru 2 with poly(U-A.•U) triplex were studied.