Peptides are short chains of amino acids joined by peptide bonds. There is no official cut-off, but a chain of up to about 50 amino acids is usually called a peptide; above that, we generally speak of a protein.
Why do they matter?
Many of the human body's hormones and signalling molecules are peptides: insulin, glucagon, GLP-1, oxytocin and vasopressin are examples. They bind specific receptors on the cell surface and trigger precise biological responses.
This specificity makes peptides attractive for pharmaceutical research: more than 80 peptide medicines are approved worldwide today, with hundreds more in clinical development.
Natural, analogue and synthetic
- Natural: identical to those produced by the body.
- Analogues: modified versions of a natural peptide designed for greater stability or longer action — semaglutide, for instance, is a GLP-1 analogue.
- Synthetic or derived: lab-designed sequences or fragments of larger proteins, such as BPC-157.
The challenges
Peptides are quickly broken down by enzymes and generally do not survive the digestive tract. That is why most peptide medicines are injectable, and much of modern peptide engineering aims to extend half-life — for example with fatty acid chains that bind to albumin.
A word of caution
A peptide having published studies does not mean it is safe or effective in humans. The gap between a result in cells or rats and an approved medicine is enormous. In our library, we show the evidence level for each molecule precisely to make that difference clear.