Base-Modified DNA Labeled by [Ru(bpy)(3)](2+) and [Os(bpy)(3)](2+) Complexes: Construction by Polymerase Incorporation of Modified Nucleoside Triphosphates, Electrochemical and Luminescent Properties, and Applications
Modified 2'-deoxynucleoside triphosphates (dNTPs) bearing [Ru(bpy)(3)](2+) and [Os(bpy)(3)](2+) complexes attached via an acetylene linker to the 5-position of pyrimidines (C and U) or to the 7-position of 7-deazapurines (7-deaza-A and 7-deaza-G) have been prepared in one step by aqueous cross-couplings of halogenated dNTPs with the corresponding terminal acetylenes. Polymerase incorporation by primer extension using Vent (exo-) or Pwo polymerases gave DNA labeled in specific positions with Ru2+ or Os2+ complexes. Square-wave voltammetry could be efficiently used to detect these labeled nucleic acids by reversible oxidations of Ru2+/3+ or Os2+/3+. The redox potentials of the Ru2+ complexes (1.1-1.25 V) are very close to that of G oxidation (1.1 V), while the potentials of Os2+ complexes (0.75 V) are sufficiently different to enable their independent detection. On the other hand, Ru2+-labeled DNA can be independently analyzed by luminescence. In combination with previously reported dNTPs bearing ferrocene, aminophenyl, and nitrophenyl tags, the Os-labeled dATP has been successfully used for "multicolor" redox labeling of DNA and for DNA minisequencing.