How sequences are written, and what the three-letter codes mean.
A peptide is a short chain of amino acids. Its sequence is the order of those amino acids, written from the N-terminus (the end with a free amino group) to the C-terminus (the end with a free carboxyl group).
Sequences are written in three-letter codes separated by hyphens, such as Gly-His-Lys, or in single-letter codes, such as GHK. Gly is glycine, His is histidine and Lys is lysine.
Complexes and modifications are noted alongside the sequence. GHK-Cu, for example, refers to the Gly-His-Lys tripeptide complexed with copper.
Molecular weight is given in g/mol or daltons (Da) and can differ between salt forms of the same peptide, so always compare it against the batch documentation.