Canonical residues use one letter: A alanine, C cysteine, D aspartate, E glutamate, F phenylalanine, G glycine, H histidine, I isoleucine, K lysine, L leucine, M methionine, N asparagine, P proline, Q glutamine, R arginine, S serine, T threonine, V valine, W tryptophan, Y tyrosine.
Research peptides cheat. Aib is aminoisobutyric acid, a helix-stabilizing non-canonical residue in Ipamorelin and Semaglutide. D-Phe means the phenylalanine is the mirror image, which proteases hate — that is the point. 2-Nal is naphthylalanine. Ac- on the left is an acetyl cap. -NH2 on the right is a C-terminal amide.
Acylation
GLP-1 analogs such as semaglutide carry a fatty diacid on a lysine. The tail binds albumin and turns a minutes-long gut hormone into a weekly molecule. When you see a twenty-digit molecular weight and a week-long half-life together, look for a lipid.
Vought prints sequences as the catalog knows them. Non-canonical monomers are written in mixed notation rather than forced into a twenty-letter alphabet that cannot hold them.