one letter code
 |
 |     symbol
 |     |
 |     |                       name
 |     |                       |

 U     U                       uridine
 C     C                       cytidine
 A     A                       adenosine
 G     G                       guanosine
 T     T                       thymine (for sequences of tRNA genes only)
 -                             empty position
 _   (underline)               insertion (see footnote for further information)
 .                             unknown nucleotide

 H     ?A                      unknown modified adenosine
 "     m1A                     1-methyladenosine
 /     m2A                     2-methyladenosine
 +     i6A                     N6-isopentenyladenosine
 *     ms2i6A                  2-methylthio-N6-isopentenyladenosine
 =     m6A                     N6-methyladenosine
 6     t6A                     N6-threonylcarbamoyladenosine
 E     m6t6A                   N6-methyl-N6-threonylcarbamoyladenosine
 [     ms2t6A                  2-methylthio-N6-threonylcarbamoyladenosine
 :     Am                      2'-O-methyladenosine
 I     I                       inosine
 O     m1I                     1-methylinosine
 ^     Ar(p)                   2'-O-ribosyladenosine (phosphat)
 `     io6A                    N6-(cis-hydroxyisopentenyl)adenosine

 <     ?C                      unknown modified cytidine
 %     s2C                     2-thiocytidine
 B     Cm                      2'-O-methylcytidine
 M     ac4C                    N4-acetylcytidine
 ?     m5C                     5-methylcytidine
 '     m3C                     3-methylcytidine
 }     k2C                     lysidine
 >     f5C                     5-formylcytidin
 °     f5Cm                    2-O-methyl-5-formylcytidin

 ;     G                       unknown modified guanosine
 K     m1G                     1-methylguanosine
 L     m2G                     N2-methylguanosine
 #     Gm                      2'-O-methylguanosine
 R     m22G                    N2,N2-dimethylguanosine
 |     m22Gm                   N2,N2,2'-O-trimethylguanosine
 7     m7G                     7-methylguanosine
 (     fa7d7G                  archaeosine
 Q     Q                       queuosine
 8     manQ                    mannosyl-queuosine
 9     galQ                    galactosyl-queuosine
 Y     yW                      wybutosine
 W     o2yW                    peroxywybutosine

 N     ?U                      unknown modified uridine
 {     mnm5U                   5-methylaminomethyluridine
 2     s2U                     2-thiouridine
 J     Um                      2'-O-methyluridine
 4     s4U                     4-thiouridine
 &     ncm5U                   5-carbamoylmethyluridine
 1     mcm5U                   5-methoxycarbonylmethyluridine
 S     mnm5s2U                 5-methylaminomethyl-2-thiouridine
 3     mcm5s2U                 5-methoxycarbonylmethyl-2-thiouridine
 V     cmo5U                   uridine 5-oxyacetic acid
 5     mo5U                    5-methoxyuridine
 !     cmnm5U                  5-carboxymethylaminomethyluridine
 $     cmnm5s2U                5-carboxymethylaminomethyl-2-thiouridine
 X     acp3U                   3-(3-amino-3-carboxypropyl)uridine
 ,     mchm5U                  5-(carboxyhydroxymethyl)uridinemethyl ester
 )     cmnm5Um                 5-carboxymethylaminomethyl-2'-O-methyluridine
 ~     ncm5Um                  5-carbamoylmethyl-2'-O-methyluridine
 D     D                       dihydrouridine
 P     psi                     pseudouridine
 ]     m1psi                   1-methylpseudouridine
 Z     psi m                   2'-O-methylpseudouridine
 T     m5U                     ribosylthymine
 F     m5s2U                   5-methyl-2-thiouridine
 \     m5Um                    5, 2'-O-dimethyluridine