What are peptides? — Peptidekennis

The short answer

A peptide is a small molecule built from a short chain of amino acids — the same building blocks that make up proteins. The difference between a peptide and a protein is mainly length: a chain of up to roughly fifty amino acids is usually called a peptide, anything longer a protein. Amino acids are linked by so-called peptide bonds, and that bond gives the class its name.

From amino acid to function

Amino acids can be thought of as letters. The order in which they are linked — the amino-acid sequence — determines the "meaning" of the molecule, just as the order of letters determines a word. That sequence gives a peptide a specific three-dimensional shape, and the shape in turn determines which structures it can interact with.

Many peptides act as signalling molecules. They fit a receptor — a kind of lock on the surface of a cell — and set off a reaction. Because a peptide often fits selectively onto a single type of receptor, the class is scientifically interesting: it allows one biological process to be studied in isolation.

Natural and synthetic peptides

Peptides occur naturally in the body. Insulin is a well-known example of an endogenous peptide (strictly a small protein) central to blood-glucose regulation. Hormones such as oxytocin are peptides too.

Peptides are also made synthetically, usually through solid-phase peptide synthesis, in which the chain is built up step by step. Synthetic peptides are used in laboratory research and in drug development. Many substances circulating online as "research peptides" fall into this category: synthetically produced molecules studied in research, but by no means always approved as medicines.

A research peptide is not a medicine

The fact that a substance is studied scientifically does not mean it is approved for use in humans. Many research peptides are at an early stage, or have only been examined in laboratory or animal studies. A substance becomes a registered medicine only after extensive clinical trials and approval by an authority such as the EMA (Europe), the FDA (United States) or the CBG (the Netherlands). Until that approval exists, a substance is not a medicine — however promising the research may look.

Why shape and stability matter

Peptides are relatively fragile molecules. They can break down under heat, light or moisture, and in the body they are often degraded quickly. That is why they are usually supplied for research as a freeze-dried (lyophilised) powder. Terms such as half-life and lyophilisation belong to these properties; both are explained in the glossary.

Frequently asked questions

Is a peptide the same as a protein? Not quite. It is the same chemistry — amino acids joined by peptide bonds — but a peptide is shorter. The boundary around fifty amino acids is a common rule of thumb, not a law of nature.

Are peptides safe? That depends entirely on the specific substance, the context, and whether it is approved. For research peptides that are not approved, safety outside controlled studies has not been established. This site makes no case-by-case statements about that; it is a question for a physician.

Why is so much of the information in English? Much of the research and much of the online supply originates in the United States. This site exists to place that information in plain language and in the right legal context.