Disclaimer: All products and information referenced are supplied strictly for laboratory and research purposes only. Nothing here is intended for human or animal consumption, nor as medical advice.
Peptides are short chains of amino acids, usually between 2 and 50, joined by peptide bonds. They are smaller than proteins and many act as signals in the body, telling cells to grow, repair, release hormones or change metabolism. This guide explains what peptides are, how they differ from proteins, how research peptides are made and the main families studied today.
What are peptides made of?
Every peptide is built from amino acids, the same 20 building blocks that make up proteins. The carboxyl group of one amino acid links to the amino group of the next, releasing a water molecule and forming a peptide bond.
The US National Human Genome Research Institute defines a peptide as a short chain of about 2 to 50 amino acids.
Peptides by length
- Dipeptides and tripeptides: 2–3 amino acids, e.g. GHK (glycine-histidine-lysine).
- Oligopeptides: up to about 20, e.g. oxytocin (9) or BPC-157 (15).
- Polypeptides: longer chains, e.g. thymosin beta-4 (43) or insulin (51).
Peptides vs proteins
| Peptides | Proteins | |
|---|---|---|
| Length | ~2–50 amino acids | Usually 50+, often hundreds |
| Structure | Simple, often flexible | Folded into complex 3D shapes |
| Typical role | Signalling and regulation | Structure, enzymes, transport |
| Example | Oxytocin, GLP-1 | Collagen, haemoglobin |
The 50-amino-acid line is a convention, not a hard rule, which is why insulin (51) is described as both.
How research peptides are made
Most research peptides are made by solid-phase peptide synthesis (SPPS), developed by Bruce Merrifield, who won the 1984 Nobel Prize in Chemistry for it. Amino acids are added one at a time to a chain anchored on a resin bead, then the finished peptide is cleaved off and purified.
From synthesis to vial
- Synthesis: chain built step by step by SPPS.
- Purification: HPLC separates the target peptide from incomplete chains.
- Testing: HPLC confirms purity; mass spectrometry confirms identity.
- Lyophilisation: the peptide is freeze-dried into a stable powder. See what lyophilised means.
For what a purity figure actually tells you, read understanding peptide purity.
The main families of research peptides
Growth hormone secretagogues
Peptides that stimulate growth hormone release, such as ipamorelin, CJC-1295 and tesamorelin.
Metabolic peptides
GLP-1 and multi-receptor agonists such as semaglutide and retatrutide, plus mitochondrial peptides like MOTS-c.
Tissue and repair peptides
BPC-157 and TB-500, studied in wound and tissue models.
Copper peptides
GHK-Cu, studied in skin and tissue remodelling.
Bioregulators
Very short Khavinson peptides such as epitalon and pinealon. See our introduction to bioregulators.
Melanocortins
Melanotan 2 and PT-141, which act on melanocortin receptors.
Peptide medicines vs research peptides
Some peptides are licensed medicines, including insulin, semaglutide and oxytocin. Research peptides are a different category: they are supplied for laboratory use and are not approved for human use. The same molecule can exist as both, but a research-grade vial is not a medicine. Our guide to UK peptide law explains the distinction.
Peptide FAQs
What is the difference between a peptide and a protein?
Length and structure. Peptides are short chains of roughly 2 to 50 amino acids; proteins are longer chains, usually over 50, that fold into complex 3D shapes.
Are peptides natural?
Many are. The body makes hundreds, including insulin, oxytocin and glutathione. Research peptides are synthetic copies or modified versions of natural sequences.
Are peptides safe?
It depends entirely on the peptide. Licensed peptide medicines have been through clinical trials; most research peptides have not, so their safety in humans is not established.
Why are research peptides sold as powder?
They are freeze-dried (lyophilised) because peptides break down much faster in solution. Powder is far more stable for storage and shipping.
Summary
Peptides are short amino-acid chains that mostly act as signals. Research peptides are synthesised by SPPS, purified by HPLC and freeze-dried for stability. To see the full range, browse the PeptidesNextDay shop: every peptide is ≥98% purity (95% for a few large proteins), with batch documentation available on request.