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An artificial nucleoside surrogate with 1H-imidazo[ 4,5-f][1,10]phenanthroline (P) acting as an aglycone has been introduced into DNA oligonucleotide duplexes. This nucleoside surrogate can act as a bidentate ligand, and so is useful in the context of metal-mediated base pairs. Several duplexes involving a hetero base pair with an imidazole nucleoside have been investigated. The stability of DNA duplexes incorporating the respective AgI-mediated base pairs strongly depends on the sequence context. Quantum mechanical/ molecular mechanical (QM/MM) calculations have been performed in order to gain insight into the factors determining this sequence dependence. The results indicated that, in addition to the stabilizing effect that results from the formation of coordinative bonds, destabilizing effects may occur when the artificial base pair does not fit optimally into the surrounding B-DNA duplex. [ABSTRACT FROM AUTHOR]

Metal-mediated base pairs represent an elegant way for the site-specific functionalisation of nucleic acids. In this type of base pair, the hydrogen bonds between complementary nucleobases are replaced formally by coordinative bonds to one or more transition-metal ions. This Review presents an overview of metal-mediated base pairs reported so far. It gives an insight into the characterisation of metal-mediated base pairs and into the structures of the resulting metal-modified nucleic acids. In addition, a summary of applications exploiting the formation of metal-mediated base pairs is presented. The applications include, for example, metal-ion sensors of various types, a protein sensor, and DNA-based molecular machines. Initial reports on the potential use of metal-mediated base pairs in the context of charge transfer through nucleic acid double helices are summarised as well. [ABSTRACT FROM AUTHOR]