What are peptides?
Peptides are short chains of amino acids, the same building blocks that make up proteins. They are smaller than proteins, usually between 2 and 50 amino acids long.
How peptides are built
Amino acids link together through a chemical bond called a peptide bond. The order of the amino acids, called the sequence, gives each peptide its structure and its properties. Changing a single amino acid can change how a peptide behaves.
Peptides, polypeptides and proteins
| Name | Typical length |
|---|---|
| Dipeptide | 2 amino acids |
| Oligopeptide | 2 to 20 amino acids |
| Polypeptide | 20 to 50 amino acids |
| Protein | More than 50 amino acids |
Where peptides are found
The body produces many peptides naturally. Some act as hormones, some as signalling molecules between cells, and others help the immune system. Peptides are also found naturally in many foods.
How laboratories make and check them
Most research peptides are produced by solid-phase peptide synthesis, a method that adds one amino acid at a time to a growing chain. After synthesis, the peptide is purified and usually freeze-dried into a stable powder.
Laboratories then check each material with two standard methods: high-performance liquid chromatography (HPLC) to measure purity, and mass spectrometry (MS) to confirm the peptide is the right molecule.
Storage
Freeze-dried peptides are usually kept cold, dry and away from light. Once dissolved, most are less stable and are stored in the refrigerator for a limited time.
Further reading
- Merrifield R. B. (1963). Solid Phase Peptide Synthesis. I. The Synthesis of a Tetrapeptide. Journal of the American Chemical Society, 85(14).
- Fenn J. B. et al. (1989). Electrospray Ionization for Mass Spectrometry of Large Biomolecules. Science, 246.
- The Nobel Prize in Chemistry 1984, awarded for solid-phase chemical synthesis. NobelPrize.org.
- Peptide. Encyclopaedia Britannica.
- High-performance liquid chromatography. Wikipedia.
This page is for general information. It is not medical advice.