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

• DOI: 10.1007/s00775-012-0950-8
• Publication Date: 2012-10-30T12:55:20Z
• Authors: Li-Feng Tan; Ling-Jun Xie; Xiao-Nan Sun
• Keywords: 0301 basic medicine; 03 medical and health sciences; Viscosity; RNA Stability; Organometallic Compounds; Temperature; Nucleic Acid Conformation; Quantum Theory; Ligands; Nucleic Acid Denaturation; Ruthenium; Polyribonucleotides

The binding properties of [RuL(2)(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.