#Order number Originating base Long abbreviation Full name Oneletter-HTML PDB abbreviation A A A adenosine A A 0A A Am 2-O-methyladenosine : MRA 1A A m1A 1-methyladenosine " 1MA 2A A m2A 2-methyladenosine / 2MA 3A A Arp 2-O-ribosyladenosine(phosphate) ^ UNK 4A A m1Am 1,2-O-dimethyladenosine œ M2A 5A A g6A N6-glycinylcarbamoyladenosine ≡ UNK 6A A m6A N6-methyladenosine = 6MA 7A A m66A N6,N6-dimethyladenosine ζ UNK 7A A m62A N6,N6-dimethyladenosine ζ UNK 8A A m6Am N6,2-O-dimethyladenosine χ MMA 9A A m66Am N6,N6,O-2-trimethyladenosine η MTA 9A A m62Am N6,N6,O-2-trimethyladenosine η MTA 10A A I inosine I MRI 11A A m1I 1-methylinosine O UNK 12A A Im 2-O-methylinosine ≤ 1MI 13A A m1Im 1,2-O-dimethylinosine ξ UNK 14A A t6A N6-threonylcarbamoyladenosine 6 UNK 15A A m6t6A N6-methyl-N6-threonylcarbamoyladenosine E 66A 16A A ms2t6A 2-methylthio-N6-threonyl_carbamoyladenosine [ UNK 17A A ms2m6A 2-methylthio-N6-methyladenosine ∞ SMA 18A A ms2hn6A 2-methylthio-N6-hydroxynorvalyl_carbamoyladenosine ≈ UNK 19A A i6A N6-isopentenyladenosine + 6IA 20A A ms2io6A 2-methylthio-N6-(cis-hydroxyisopentenyl) adenosine ≠ SIA 21A A ms2i6A 2-methylthio-N6-isopentenyladenosine * SPA 22A A io6A N6-(cis-hydroxyisopentenyl)adenosine ` UNK 23A A hn6A N6-hydroxynorvalylcarbamoyladenosine √ HNA 24A A ac6A N6-acetyladenosine @ 6AA 25A A m8A C8-methyladenosine @ UNK C C C cytosine C C 0C C Cm 2-O-methylcytidine B MRC 1C C k2C lysidine } UNK 2C C s2C 2-thiocytidine % 2SC 3C C m3C 3-methylcytidine ' 3MC 4C C m4C N4-methylcytidine ν 4MC 5C C m5C 5-methylcytidine ? UNK 6C C ac4C N4-acetylcytidine M 4AC 7C C ac4Cm N4-acetyl-2-O-methylcytidine ℵ MAC 8C C m4Cm N4,2-O-dimethylcytidine λ UNK 9C C m44C N4,N4-dimethylcytidine @ UNK 9C C m42C N4,N4-dimethylcytidine @ UNK 10C C m44Cm N4,N4,2-O-trimethylcytidine β UNK 10C C m42Cm N4,N4,2-O-trimethylcytidine β UNK 11C C m5Cm 5,2-O-dimethylcytidine τ UNK 12C C f5C 5-formylcytidine > 5FC 13C C f5Cm 5-formyl-2-O-methylcytidine ° UNK 14C C hm5C 5-hydroxymethylcytidine ∅ HMC G G G guanosine G G 0G G Gm 2-O-methylguanosine # MRG 1G G m1G 1-methylguanosine K 1MG 2G G m2G N2-methylguanosine L 2MG 3G G m22G N2,N2-dimethylguanosine R UNK 4G G m22Gm N2,N2,2-O-trimethylguanosine | MTG 5G G Grp 2-O-ribosylguanosine(phosphate) ℑ UNK 6G G G+ archaeosine ( UNK 6G G fa7d7G archaeosine ( UNK 7G G m7G 7-methylguanosine 7 7MG 8G G m7m2G N2,7-dimethylguanosine ∨ 27G 9G G m7m22G N2,N2,7-trimethylguanosine ∠ N2G 10G G imG wyosine Ÿ UNK 11G G m1Gm 1,2-O-dimethylguanosine ε UNK 12G G m2Gm N2,2-O-dimethylguanosine γ MMG 13G G mimG methylwyosine ∑ UNK 14G G imG-14 4-demethylwyosine † DWG 15G G imG2 isowyosine ⊇ UNK 16G G yW wybutosine Y WBG 17G G oHyW hydroxywybutosine ⊆ UNK 18G G oHyWx undermodified hydroxywybutosine š UNK 19G G o2yW peroxywybutosine W UNK 58G G yW-58 10-glutamylmethylesterwyosine @ UNK 72G G yW-72 10-glutamylwyosine @ UNK 86G G yW-86 10-glutamyl-4-demethylwyosine @ UNK Q G QtRNA queuosine Q Q 1Q G Qbase Qbase ∴ UNK 2Q G preQ0tRNA 7-cyano-7-deazaguanosine φ DCG 3Q G preQ1base preQ1base ∇ UNK 4Q G preQ1tRNA 7-aminomethyl-7-deazaguanosine ∉ UNK 5Q G oQtRNA epoxyqueuosine σ UNK 6Q G galQtRNA galactosyl-queuosine 9 UNK 7Q G manQtRNA mannosyl-queuosine 8 UNK 8Q G gluQtRNA gluQtRNA ⊄ UNK 9Q G preQ0base preQ0base ψ UNK U U U uracil U U 0U U Um 2-O-methyluridine J MRU 1U U Y pseudouridine P 13P 2U U s2U 2-thiouridine 2 2SU 3U U m3U 3-methyluridine δ 3MU 4U U s4U 4-thiouridine 4 4SU 5U U m5U 5-methyluridine T 5MU 6U U D dihydrouridine D H2U 7U U m1Y 1-methylpseudouridine ] 1MP 8U U m1acp3Y 1-methyl-3-(3-amino-3-carboxypropyl)pseudouridine α OCU 9U U Ym 2-O-methylpseudouridine Z MRP 10U U m3Y 3-methylpseudouridine κ 3MP 11U U se2U se2U ω UNK 12U U s2Um 2-thio-2-O-methyluridine ∏ MSU 13U U m3Um 3,2-O-dimethyluridine σ UNK 14U U acp3U 3-(3-amino-3-carboxypropyl)uridine X UNK 15U U acp3Um 3-(3-amino-3-carboxypropyl)methyluridine † UNK 16U U m5Um 5,2-O-dimethyluridine \ UNK 17U U m5s2U 5-methyl-2-thiouridine F 52U 18U U f5U 5-formyl-methyluridine ⊂ UNK 19U U f5Um 5-formyl-O-dimethyluridine ⊃ UNK 20U U f5s2U 5-formyl-2-thiouridine ⊗ UNK 21U U f5se2U 5-formyl-2-selenuoridine ⊕ UNK 22U U ho5U 5-hydroxyuridine ∝ 5HU 23U U mo5U 5-methoxyuridine 5 UNK 24U U nm5U 5-methylaminouridine ∪ UNK 25U U nm5s2U 5-aminomethyl-2-thiouridine ∫ SAU 26U U nm5se2U 5-aminomethyl-2-selenouridine π UNK 27U U mnm5U 5-methylaminomethyluridine { 5AU 28U U mnm5s2U 5-methylaminomethyl-2-thiouridine S ESU 29U U mnm5se2U 5-methylaminomethyl-2-selenouridine ≅ SEU 30U U cmnm5U 5-carboxymethylaminomethyluridine ! 5DU 31U U cmnm5Um 5-carboxymethylaminomethyl-2-O-methyluridine ) UNK 32U U cmnm5s2U 5-carboxymethylaminomethyl-2-thiouridine $ SCU 33U U cmnm5se2U 5-carboxymethylaminomethyl-2-selenouridine ⊥ UNK 34U U cm5U 5-carboxymethyluridine ◊ 5CU 35U U cm5s2U 5-carboxymethyl-2-thiouridine ℘ UNK 36U U chm5U 5-(carboxyhydroxymethyl)uridine ≥ HCU 37U U mcm5U 5-methoxycarbonylmethyluridine 1 MEU 38U U mcmo5U uridine 5-oxyacetic acid methyl ester υ OEU 39U U mcm5Um 5-methoxycarbonylmethyl-2-O-methyluridine ∩ UNK 40U U mcm5s2U 5-methoxycarbonylmethyl-2-thiouridine 3 SMU 41U U mchm5U 5-(carboxyhydroxymethyl)uridine methyl ester , UNK 42U U ncm5U 5-carbamoylmethyluridine & BCU 43U U ncm5Um 5-carbamoylmethyl-2-O-methyluridine ~ UNK 44U U tm5U 5-taurinomethyluridine ∀ 5TU 45U U tm5s2U 5-taurinomethyl-2-thiouridine ∃ STU 46U U cmo5U uridine 5-oxyacetic acid V OEU 47U U m5D 5-methyldihydrouridine ρ DMU # unknown H A ?A Unknown modified adenosine H UNK < C ?C Unknown modified cytidine < UNK ; G ?G Unknown modified guanosine ; UNK N U ?U Unknown modified uridine N UNK X X X Unknown . UNK x x x No one-letter-abbrev x x 0X X Xm Unknown 2'OH methylated base @ UNK # Desoxynucleotides a A dA desoxyadenosine a a g G dG desoxyguanosine g g c C dC desoxycytosine c c t U dT desoxythymidine t t # Insertion _ _ _ insertion _ _ # Missing residue - - - missing residue - - # empty space for representing modifications in new nomenclature # empty space