Peptides are short amino-acid chains that sit between single residues and full proteins. Here is a complete research reference on their structure, classification, and verification.
A peptide is a short chain of amino acids linked by covalent amide (peptide) bonds. By convention, chains of roughly 2 to 50 residues are called peptides; longer sequences are described as proteins. In the research supply chain, peptides are produced through solid-phase synthesis (SPPS) and characterised by chromatography and mass spectrometry before release.
How peptides are classified
- By length: dipeptides, oligopeptides (up to ~10 residues) and polypeptides (>10).
- By origin: naturally occurring fragments (e.g. GHK), synthetic analogs (e.g. semaglutide) and cyclic peptides (e.g. Melanotan 2).
- By function studied: metabolic, regenerative, cosmetic, neuroendocrine, immunomodulatory, longevity.
How research-grade peptides are made
- Solid-phase Fmoc synthesis: residues are added one at a time to a resin-bound C-terminus.
- Cleavage from resin and global side-chain deprotection using TFA cocktails.
- Reverse-phase HPLC purification to remove deletion sequences and truncations.
- Lyophilisation into the finished amorphous powder.
- QC by analytical HPLC, LC-MS, and where required, endotoxin and residual solvent testing.
What defines research-grade material
- Batch identifier and synthesis date traceable to the lot record
- HPLC purity ≥98% (typically ≥99% for peptides under 30 residues)
- LC-MS confirmed monoisotopic or average mass within ±0.5 Da of theoretical
- Counterion identity and content (acetate or trifluoroacetate) reported
- Bacterial endotoxin and residual solvents per the analytical method
Frequently asked
Are peptides the same as proteins?
Chemically they are the same class of molecule. The distinction is length: peptides are short, proteins are long and typically fold into a defined tertiary structure.
Why does purity matter for research?
Impurities include deletion sequences, oxidation products, and counterion salts. Purity below ~95% introduces confounders that make in-vitro results non-reproducible.
