Binding properties of Ru(II) polypyridyl complexes with poly(U)·poly(A)*poly(U) triplex: The ancillary ligand effect on third-strand stabilization

摘要

The binding properties of [RuL2(mip)]~(2+) {where L is 1,10-phenanthroline (phen) or 4,7-dimethyl-1,10-phenanthrollne (4,7-dmp) and mip is 2′-(3″,4″-methylenedioxyphenyl)imidazo[4′,5′- f][1,10]phenanthroline} with regard to the triplex RNA poly(U)·poly(A) *poly(U) were investigated using various biophysical techniques and quantum chemistry calculations. In comparison with [Ru(4,7-dmp) 2(mip)]2+, remarkably higher binding affinity of [Ru(phen)2(mip)]2+ for the triplex RNA poly(U)·poly(A)*poly(U) was achieved by changing the ancillary ligands. The stabilization of the Hoogsteen-base-paired third strand was improved by about 10.9 C by [Ru(phen)_2(mip)]~(2+) against 6.6 C by [Ru(4,7-dmp)_2(mip)]~(2+). To the best of our knowledge, [Ru(phen)_2(mip)]~(2+) is the first metal complex able to raise the third-strand stabilization of poly(U)·poly(A)*poly(U) from 37.5 to 48.4 C. The results reveal that the ancillary ligands have an important effect on third-strand stabilization of the triplex RNA poly(U)·poly(A)*poly(U) when metal complexes contain the same intercalative ligands.