Unnatural base pairs display unique abilities in duplex DNA and in nucleic acid and protein biosyntheses. A standard Watson and Crick base pair is formed between iso-C and iso-G, but the hydrogen bonding pattern is quite different from the natural base pairs A-T and C-G. Iso-bases can, therefore, increase specificity of nucleic acid hydridization when introduced as a third base pair. It has also been demonstrated that iso-bases 5-Me-iso-dC and iso-dG can function as degenerate pyrimidine and purine bases, respectively. Iso-dG further functioned as a degenerate base opposite B (C, T, and G) ambiguous sites.
