DNA Duplex Stability of the Thio-Iso-Guanine•Methyl-Iso-Cytosine Base Pair

We report the synthesis, incorporation into oligonucleotides, and base-pairing properties of the 2-thio-variant of iso-guanine. Iso-guanine is the purine component of a nonstandard base pair with 5-methyl-iso-cytosine. The 2-thio-iso-guanine•5-methyl-iso-cytosine base pair is found to have similar stability to an adenine•thymine pair.