Isoguanine
{{chembox
| ImageFile=Isoguanine Structural formula V1.svg
| ImageSize=150px
| PIN=6-Amino-1,9-dihydro-2H-purin-2-one
| OtherNames=2-Hydroxyadenine
|Section1={{Chembox Identifiers
| ChemSpiderID = 69351
| InChI1 = 1/C5H5N5O/c6-3-2-4(8-1-7-2)10-5(11)9-3/h1H,(H4,6,7,8,9,10,11)
| InChIKey1 = DRAVOWXCEBXPTN-UHFFFAOYAU
| CASNo=3373-53-3
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = E335PK4428
| PubChem=76900
| EINECS=222-157-6
| SMILES = O=C1\N=C2\N=C/NC2=C(\N1)N
}}
|Section2={{Chembox Properties
| Formula=C5H5N5O
| MolarMass=151.1261
| Appearance=
| Density=
| MeltingPt=
| BoilingPt=
| Solubility=
}}
|Section3={{Chembox Hazards
| MainHazards=
| FlashPt=
| AutoignitionPt =
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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.{{cite journal |vauthors=Yang XL, Sugiyama H, Ikeda S, Saito I, Wang AH |title=Structural studies of a stable parallel-stranded DNA duplex incorporating isoguanine:cytosine and isocytosine:guanine basepairs by nuclear magnetic resonance spectroscopy |journal=Biophys. J. |volume=75 |issue=3 |pages=1163–1171 |year=1998 |pmid=9726918 |doi=10.1016/S0006-3495(98)74035-4 |pmc=1299791|bibcode=1998BpJ....75.1163Y }} It is also used in combination with isocytosine in studies of unnatural nucleic acid analogues of the normal base pairs in DNA.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 ({{doi|10.1002/qua.560280720}}).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 ({{doi|10.1021/ja970123s}}).
It is used as a nucleobase of hachimoji nucleic acids.{{cite journal|last=Hoshika|first=Shuichi|display-authors=etal|date=22 February 2019|title=Hachimoji DNA and RNA: A genetic system with eight building blocks |journal=Science|volume=363|issue=6429|pages=884–887|doi=10.1126/science.aat0971|pmid=30792304|pmc=6413494|bibcode=2019Sci...363..884H}} In hachimoji DNA, it pairs with 1-methylcytosine, while in hachimoji RNA, it pairs with isocytosine.
