A stable zinc(II)-mediated base pair in a parallel-stranded DNA duplex.

A stable zinc(II)-mediated base pair was formed within a parallel-stranded DNA duplex comprising a GNA (glycol nucleic acid) functionalized nucleoside analog containing the artificial nucleobase 1H-imidazo[4,5-f][1,10]phenanthroline (P). The formation of the metal-mediated base pair was confirmed by UV and CD spectroscopic analyses. In the Zn(II)-mediated homo base pairs of the type P-Zn(II)-P, the metal ion adopts a [2 + 2] coordination environment. CD spectroscopic data suggest that the chiral metal complex is formed enantiospecifically, likely induced by the helical chirality of the surrounding DNA duplex. The Zn(II)-mediated base pair stabilizes the DNA oligonucleotide duplex by 9 °C. This stable Zn(II)-mediated base pair within a parallel-stranded duplex extends the scope of site-specific functionalization of nucleic acids by virtue of metal-mediated base pairing.