1-Methylcytosine

1-Methylcytosine (1mC) is a methylated form of the nucleic acid base cytosine. The deoxyribonucleoside it forms is called N¹-methyl-2'-deoxy-pseudocytidine (m¹Î¨dC).

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1-Methylcytosine

Names
Preferred IUPAC name 4-Amino-1-methylpyrimidin-2(1H)-one
Identifiers
CAS Number	1122-47-0 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:39624 Y
ChEMBL	ChEMBL500883
ChemSpider	71474 Y
MeSH	1-Methylcytosine
PubChem CID	79143
UNII	1J54NE82RV Y
CompTox Dashboard (EPA)	DTXSID60149949
InChI InChI=1S/C5H7N3O/c1-8-3-2-4(6)7-5(8)9/h2-3H,1H3,(H2,6,7,9) Y Key: HWPZZUQOWRWFDB-UHFFFAOYSA-N Y InChI=1S/C5H7N3O/c1-8-3-2-4(6)7-5(8)9/h2-3H,1H3,(H2,6,7,9) Key: HWPZZUQOWRWFDB-UHFFFAOYSA-N
SMILES CN1C=CC(=NC1=O)N
Properties
Chemical formula	C5H7N3O
Molar mass	125.131 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 Â°C [77 Â°F], 100 kPa). Infobox references

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In 1-methylcytosine, a methyl group is attached to the 1st atom in the 6-atom ring. This methyl group distinguishes 1-methylcytosine from cytosine. The location distinguishes it from the more (naturally) common 5-methylcytosine.

1mC forms hydrogen bonds differently compared to cytosine because it attaches to the backbone sugar (ribose or deoxyribose) differently: at the C5 position as opposed to cytidine's C1 position, analogous to the difference between pseudouridine and uridine. It pairs with isoguanine in Artificially Expanded Genetic Information System (hachimoji) DNA, replacing the unstable deoxyribonucleoside form of isocytosine.^[1]