Isoguanine Explained

Isoguanine or 2-hydroxyadenine is a purine base that is an isomer of guanine. It is a product of oxidative damage to DNA and has been shown to cause mutation.^[1] It is also used in combination with isocytosine in studies of unnatural nucleic acid analogues of the normal base pairs in DNA.^{[2] [3]}

It is used as a nucleobase of hachimoji nucleic acids.^[4] In hachimoji DNA, it pairs with 1-methylcytosine, while in hachimoji RNA, it pairs with isocytosine.

References

1. Yang XL, Sugiyama H, Ikeda S, Saito I, Wang AH . Structural studies of a stable parallel-stranded DNA duplex incorporating isoguanine:cytosine and isocytosine:guanine basepairs by nuclear magnetic resonance spectroscopy . Biophys. J. . 75 . 3 . 1163–1171 . 1998 . 9726918 . 10.1016/S0006-3495(98)74035-4 . 1299791. 1998BpJ....75.1163Y .
2. Andrzej Jaworski, Józef S. Kwiatkowski, Bogdan Lesyng: „Why isoguanine and isocytosine are not the components of the genetic code", International Journal of Quantum Chemistry, Supplement: Proceedings of the International Symposium on Quantum Biology and Quantum Pharmacology, 1985, 28 (Supplement S12), pp. 209–216 .
3. Christopher Roberts, Rajanikanth Bandaru, Christopher Switzer: „Theoretical and Experimental Study of Isoguanine and Isocytosine:  Base Pairing in an Expanded Genetic System", J. Am. Chem. Soc., 1997, 119 (20), pp. 4640–4649 .
4. Hoshika. Shuichi. etal. 22 February 2019. Hachimoji DNA and RNA: A genetic system with eight building blocks . Science. 363. 6429. 884–887. 10.1126/science.aat0971. 30792304. 6413494. 2019Sci...363..884H.