The proteinogenic amino acids are designated by their standard three-letter code abbreviation. Additionally, the one-letter code is used for denoting the sequences of peptides. Common three-letter abbreviations are used as well for common “unusual” amino acids, e.g. H-Hyp-OH – L-cis-hydroxyproline, H-Nle-OH – L-norleucine.

Pyroglutamyl is abbreviated as Pyr (quite a number of abbreviations is in use for this most important peptide modification, IUPAC/IUB: Glp). For designations of other amino acids please see the glossary. Some abbreviations differ from literature use and IUPAC/IUB recommendations.