DNA Oligomers and Duplexes Containing a Covalently Attached Derivative of Tris(2,2'-bipyridine)ruthenium(II): Synthesis and Characterization by Thermodynamic and Optical Spectroscopic Measurements

Article abstract of DOI:10.1021/ja00200a049

Oligonucleotides having the base sequence 5'-GCA(C^*)TCAG-3' and 5'-GCAC(T^*)CAG-3' were synthesized where C^* and T^* equal, respectively, a chemical modified cytidine or thymidine base containing a linker arm terminating in a primary amine.The primary amine of these modified oligomers reacted specifically with the N-hydroxysuccinimide ester of 4-carboxy-4'-methyl-2,2'-bipyridine to form bipyridine-labeled oligomers, and these oligomers reacted with Ru(bpy)2(H2O)2(2+) to give oligonucleotides with covalently attached derivatives of Ru(bpy)3(2+).Oligonucleotideswith nonspecifically bound Ru(bpy)2(H2O)x(2+), where x=0 or 1, were also formed, but were chromatographically separated from the former product.Duplexes of the Ru(bpy)3(2+)-labeled oligonucleotides were formed upon addition of their unmodified complementary strands and were studied by melting temperature behavior as a function of concentration and by absorption and emission optical spectroscopies.Both hybridization behavior and the spectroscopic properties of the ruthenium label itself were retained in these labeled duplexes.This work shows that it is possible to use DNA duplexes as molecular scaffolds to organize covalently attached polypyridyl-substituted transition-metal complexes and constitutes an initial step in the construction of macromolecules with specifically located, redox-active subunits.