FundamentalsGuide
What Are Peptides?
Chains of amino acids, and how research peptides are made.
On this page5 sections
A peptide is a short chain of amino acids. That one sentence covers the chemistry; everything else on this page is about what follows from it — how peptides differ from proteins, how they are made, and how a laboratory establishes that the vial contains what the label says.
This page describes peptides as research materials. It contains no dosing information and no guidance on use in humans or animals. Everything Horizon Peptides supplies is for laboratory and research purposes only.
The short answer
Amino acids are the building blocks. Link two of them together and you have a dipeptide; link a few dozen and you have a peptide. Keep going past roughly fifty residues and the same molecule is conventionally called a protein. There is no hard chemical boundary at fifty — the distinction is one of size and convention rather than of kind.
| Term | Roughly | Example from this catalogue |
|---|---|---|
| Amino acid | A single building block | Not sold on its own here |
| Peptide | 2 to about 50 amino acids | BPC-157 is 15 residues |
| Polypeptide | Longer chains, loosely the same thing | Most of the longer sequences in this catalogue |
| Protein | Above about 50, usually folded into a structure | Outside what this shop supplies |
What makes peptides interesting to researchers is that the order of the amino acids is the information. Change one residue and you change the molecule, which is why a sequence is written out and published rather than described loosely, and why two vials labelled with the same name should contain the same sequence.
How a research peptide is made
Almost all research peptides are built by solid-phase peptide synthesis. The chain is assembled one amino acid at a time on a solid resin support, each new residue coupled to the growing chain and then the protecting group removed before the next one is added. When the sequence is complete the chain is cleaved from the resin and purified.
Two consequences of that process matter when you are buying:
- Synthesis is never perfect. Some chains fail to extend at a given step, which produces closely related sequences missing a residue. Purification removes most of them. The purity figure on a certificate is largely a statement about how much of that material was removed.
How researchers group them
Peptides are usually organised by the pathway or system a study is interested in rather than by chemistry. These are the groupings used across this catalogue:
- Recovery — sequences studied in tissue repair and inflammatory signalling.
- Cognitive — sequences studied for activity in the central nervous system.
- Metabolic — sequences studied in metabolic and appetite-regulation research.
- Longevity — sequences studied in cellular ageing research.
- Skin — including GHK-Cu, the copper-binding tripeptide.
- Sleep and immune — smaller groups, same principle.
A grouping describes what a sequence has been studied in relation to. It is not a claim about an effect, and nothing on this site should be read as one.
Reading a certificate of analysis
A certificate of analysis is the only part of a peptide purchase that can be checked independently. It is worth knowing how to read one before you rely on it.
- Who ran the test. Analysis carried out by the manufacturer is not the same as analysis carried out by a third party.
- The method. HPLC-UV separates a sample by pushing it through a column and records what emerges and when. The purity figure is the main peak as a proportion of everything detected.
- What the figure does not say. A high purity number describes the proportion of the sample that is the main compound. It does not by itself confirm the identity of that compound; mass spectrometry is what addresses identity.
- The batch number. A certificate describes one batch. A certificate for a different batch tells you about the supplier, not about the vial in your hand.
Not every batch has a published certificate.
Questions this page is deliberately not answering
Two of the most common searches around peptides are about benefits and about side effects. Both are questions about what a compound does in a person, and this site does not answer them — not because the question is unreasonable, but because everything here is supplied for laboratory research and answering it would be a claim we are not in a position to make. If that is what you are looking for, the right source is a clinician or the published literature, not a shop.