Table II Amino acid three and single letter codes, plus amino acid residue masses and elemental composition. Residue mass is defined as the amino acid minus water (i.e., NH-CHR-CO)
Residue3/1 letter codeCompositionMono. massAvg. mass
AlanineAla/AC3N5NO71.0371271.08
ArginineArg/RC6H12N4O156.10112156.19
AsparagineAsn/NC4H6N2O2114.04293114.10
Aspartic acidAsp/DC4H5NO3115.02695115.09
CysteineCys/CC3H5NOS103.00919103.14
Cysteine-cmaCys/CC5H8N2O2S160.03065160.20
GlutamineGln/QC5H8N2O2128.05858128.13
Glutamic acidGlu/EC5H7NO3129.04260129.12
GlycineGly/GC2H3NO57.0214757.05
HistidineHis/HC6H7N3O137.05891137.14
IsoleucineIle/IC6H11NO113.08407113.16
LeucineLeu/LC6H11NO113.08407113.16
LysineLys/KC6H12N2O128.09496128.17
MethionineMet/MC5H9OS131.04049131.19
Methionine-oxbMet/MC5H9O2S147.03540147.18
PhenylalaninePhe/FC9H9NO147.06842147.18
ProlinePro/PC5H7NO97.0527797.12
SerineSer/SC3H5NO287.0320387.08
ThreonineThr/TC4H7NO2101.04768101.10
TryptophanTrp/WC11H10N2O186.07932186.21
TyrosineTyr/YC9H9NO2163.06333163.18
ValineVal/VC5H9NO99.0684299.13
  • a Carbamidomethylated cysteine.

  • b Oxidized methionine.