Metal-Dependent Nucleobase Recognition by Picolinamide

A C‐nucleoside featuring picolinamide as the base moiety has been synthesized and incorporated in the middle of a DNA oligonucleotide. The melting temperatures of duplexes formed by this modified oligonucleotide with its unmodified counterparts placing either adenine, cytosine, guanine or thymine opposite to the picolinamide residue were found to be highly dependent on the identity and concentration of transition metal ions in the samples. For example, AgI uniquely promoted pairing with adenine and PdII with guanine. Pairing with cytosine, on the other hand, was retarded by all of the metal ions studied (AgI, CuII, HgII, NiII, PdII and ZnII). Mix and match: Within a DNA oligonucleotide, a picolinamide residue exhibits different base pairing preferences in the presence of different transition metal ions (see figure). The highest affinity and selectivity was observed in the presence of PdII ions and guanine was the preferred base pairing partner.