Definition
A peptide is a short chain of amino acids joined by peptide bonds. Conventionally, chains of roughly 2 to 50 residues are called peptides, while longer chains that fold into stable tertiary structures are called proteins. The boundary is a matter of convention rather than chemistry.
Nomenclature you will see
- Dipeptide, tripeptide: two or three residues
- Oligopeptide: a short chain, typically under ten residues
- Polypeptide: a longer chain approaching protein length
- Cyclic peptide: a chain closed into a ring, often more stable to proteolysis
How research peptides are made
Most research peptides are produced by solid-phase peptide synthesis. The chain is assembled one protected amino acid at a time on an insoluble resin, then cleaved, purified by preparative HPLC and lyophilised into a dry powder. Purity figures on a certificate of analysis describe how cleanly that purification ran.
Why they are studied
Peptides sit between small molecules and biologics. They can be highly selective for a receptor while remaining small enough to synthesise cheaply and modify systematically, which makes them useful tools for probing signalling pathways in cell culture and other in-vitro models.
- Receptor binding and selectivity studies
- Enzyme substrate and inhibition assays
- Structure-activity relationship mapping across analogues
- Analytical method development and reference standards
Important limitation
Research peptides are unlicensed laboratory chemicals. Nothing on this page describes or endorses use in humans or animals.