Peptide Nomenclature Guide
Symbols and structures for amino acids
Common (“proteinogenic” or “coded”) amino acids have a three-letter symbol and are also represented by a one-letter symbol. Uncommon amino acids also have three-letter symbols and can be represented by the one-letter symbol “X”. The tables below list the symbols and abbreviations used in our website and literature.
Table 1. Common Amino Acids
| Amino acid | Three-letter symbol | One-letter symbol | Properties | Chemical structure |
|---|---|---|---|---|
| Alanine | Ala | A | Non-Polar (hydrophobic) | 
|
| Arginine | Arg | R | Basic | 
|
| Asparagine | Asn | N | Polar (uncharged) | 
|
| Aspartic acid | Asp | D | Acidic | 
|
| Cysteine | Cys | C | Polar (uncharged) | 
|
| Glutamine | Gln | Q | Polar (uncharged) | 
|
| Glutamic acid | Glu | E | Acidic | 
|
| Glycine | Gly | G | Polar (uncharged) | 
|
| Histidine | His | H | Basic | 
|
| Isoleucine | Ile | I | Non-Polar (hydrophobic) | 
|
| Leucine | Leu | L | Non-Polar (hydrophobic) | 
|
| Lysine | Lys | K | Basic | 
|
| Methionine | Met | M | Non-Polar (hydrophobic) | 
|
| Phenylalanine | Phe | F | Non-Polar (hydrophobic) | 
|
| Proline | Pro | P | Non-Polar (hydrophobic) | 
|
| Serine | Ser | S | Polar (uncharged) | 
|
| Threonine | Thr | T | Polar (uncharged) | 
|
| Tryptophan | Trp | W | Non-Polar (hydrophobic) | 
|
| Tyrosine | Tyr | Y | Polar (uncharged) | 
|
| Valine | Val | V | Non-Polar (hydrophobic) | 
|
Table 2. Uncommon Amino Acids
| Three letter symbol | Amino Acid |
|---|---|
| Aad | 2-Aminoadipic acid (2-aminohexanedioic acid) |
| Aan | α-Asparagine |
| Abu | 2-Aminobutanoic acid |
| Aca | 2-Aminocapric acid (2-aminodecanoic acid) |
| Agn | α-Glutamine |
| Ahx | 6-Aminohexanoic acid |
| Aib | α-Aminoisobutyric acid (α-methylalanine) |
| Apm | 2-Aminopimelic acid (2-aminoheptanedioic acid) |
| App | γ-Amino-β-hydroxybenzenepentanoic acid |
| Asu | 2-Aminosuberic acid (2-aminooctanedioic acid) |
| AzaGly | 2-Azaglycine |
| Aze | 2-Carboxyazetidine |
| Bal | β-Alanine |
| Bas | β-Aspartic acid |
| Bly | 3,6-Diaminohexanoic acid (β-lysine) |
| Bua | Butanoic acid |
| Bux | 4-Amino-3-hydroxybutanoic acid |
| Cap | γ-Amino-β-hydroxycyclohexanepentanoic acid |
| Cha | 3-Cyclohexylalanine |
| Cit | N5-Aminocarbonylornithine |
| Cya | 3-Sulfoalanine |
| Dab | 2,4-Diaminobutanoic acid |
| Dap | Diaminopropionic acid |
| Dpm | Diaminopimelic acid |
| Dpr | 2,3-Diaminopropanoic acid |
| Dsu | 2,7-Diaminosuberic acid (2,7-diaminooctanedioic acid) |
| Edc | S-Ethylthiocysteine |
| Ggu | γ-Glutamic acid |
| Gla | γ-Carboxyglutamic acid |
| Glc | Hydroxyacetic acid (glycolic acid) |
| Glp | Pyroglutamic acid (Pyr) (pGlu) |
| Har | Homoarginine |
| Hcy | Homocysteine |
| Hhs | Homohistidine |
| Hiv | 2-Hydroxyisovaleric acid |
| Hse | Homoserine |
| Hva | 2-Hydroxypentanoic acid |
| Hyl | 5-Hydroxylysine |
| Hyp | 4-Hydroxyproline |
| Igl | α-Amino-2-indanacetic acid |
| Iva | Isovaline |
| Lac | 2-Hydroxypropanoic acid (lactic acid) |
| Maa | Mercaptoacetic acid |
| Mba | Mercaptobutanoic acid |
| Mhp | 3-Hydroxy-4-methylproline |
| Mpa | Mercaptopropanoic acid |
| Nal | 3-Naphthylalanine |
| Nle | Norleucine |
| Nphe | N-Benzylglycine |
| Nty | Nortyrosine |
| Nva | Norvaline |
| Oaa | ω-Amino acid |
| Oic | 2-Carboxyoctahydroindole |
| Orn | Ornithine |
| 3-Pal | 3-(3-Pyridyl)-alanine |
| Pen | Penicillamine (3-mercaptovaline) |
| Phg | 2-Phenylglycine |
| Pip | 2-Carboxypiperidine |
| Pmp | β,β-Cyclopentamethylene-β-Mercaptopropionic acid |
| pSer | Phospho-L-serine |
| pThr | Phospho-L-threonine |
| pTyr | Phospho-L-tyrosine |
| Pya(4) | 3-(4-Pyridinyl)-alanine |
| Sar | Sarcosine (N-methylglycine) |
| Spg | 1-Amino-1-carboxycyclopentane |
| Sta | Statine ((3S,4S)-4-amino-3-hydroxy-6-methylheptanoic acid) (AHMHA) |
| Thi | 3-Thienylalanine |
| Tac | 2-Tolylaminophenylcabonyl ([(2-Methylphenyl)amino]carbonyl) |
| Tic | 3-Carboxyisoquinoline |
| Tle | 3-Methylvaline |
| Tml | ε-N-Trimethyllysine |
| Tza | 3-Thiazolylalanine |
| Und | Undefined |
| Wil | α-Amino-2,4-dioxopyrimidinepropanoic acid |