Reference

Reading peptide sequences and formulas

Every Chainwell product page lists a sequence, a molecular formula and a molecular weight. Here is how to read them.

Direction and codes

Sequences are written from the N-terminus (the free amino end) to the C-terminus (the free carboxyl end). Each amino acid has a three-letter code and a one-letter code: alanine is Ala or A, glutamic acid is Glu or E, aspartic acid is Asp or D, glycine is Gly or G. So Ala-Glu-Asp-Gly and AEDG describe the same tetrapeptide, Epitalon.

End caps

• Ac- at the start means the N-terminus is acetylated, as in TB-500 (Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH).
• -NH2 at the end means the C-terminus is an amide rather than a free acid, as in Ipamorelin.
• -OH or H- spell out a free acid or free amine end.

D-amino acids and non-standard residues

Natural proteins use L-amino acids. A D- prefix marks the mirror-image form, often used in synthetic peptides. Some sequences include residues outside the standard twenty, such as Aib (2-aminoisobutyric acid) and 2Nal (3-(2-naphthyl)alanine), both found in Ipamorelin.

Metal complexes

A few compounds are peptides bound to a metal ion. GHK-Cu is the tripeptide Gly-His-Lys complexed with copper(II), so its formula includes Cu.

Molecular formula and weight

The molecular formula counts every atom in the molecule. The molecular weight we list is the average molecular weight in g/mol, which is what you use to convert between mass and moles. Mass spectrometry reports may instead show the monoisotopic mass, which is slightly lower for large peptides. Salt forms (acetate, trifluoroacetate) add counter-ions that the free-peptide formula doesn't include.

All of our compounds' sequences, formulas and weights are listed side by side in the peptide reference table.

Chainwell products are for in-vitro laboratory research only and are not for human or veterinary use.