N-terminus & C-terminus
Also known as: N-terminal · C-terminal · amino terminus · carboxyl terminus
The two ends of a peptide chain: the N-terminus has a free amino group, the C-terminus a free carboxyl group.
Every linear peptide has two distinct ends. The N-terminus (amino terminus) is the end with a free –NH₂ group; the C-terminus (carboxyl terminus) is the end with a free –COOH group. Sequences are written and numbered from N to C.
The ends matter for stability and activity: many research peptides carry chemical modifications at one terminus — such as an amidated C-terminus or an acetylated N-terminus — specifically to slow enzymatic breakdown.
When a peptide is described as, say, a "C-terminal fragment" of a larger hormone, this is the region being referenced.
RELATED TERMS
Amino-Acid Sequence
The specific order of amino-acid residues in a peptide — its "primary structure" — which dictates shape and activity.
Peptide Bond
The covalent amide bond linking amino acids into a peptide chain — the defining structural feature of every peptide.
Amino Acid
The building-block molecules of peptides and proteins; each contributes one residue to the chain.
Analog
A peptide deliberately modified from a natural sequence to improve stability, selectivity or potency.
Half-Life
The time for a compound’s concentration to fall by half — a key determinant of dosing frequency in research.
Educational content, not medical advice. All products supplied for research purposes only — not for human consumption.