The short definition
A peptide is a short chain of amino acids linked together by peptide bonds. Amino acids are the same building blocks that make up proteins, so a peptide is essentially a very short protein fragment. Chains are generally called peptides up to roughly 50 amino acids and proteins beyond that, though the line is not precise.
Each amino acid in the chain is called a residue. A chain of two residues is a dipeptide, three is a tripeptide, and longer chains are oligopeptides or polypeptides. The specific sequence of residues — which amino acids, and in what order — defines the peptide and its properties.
Peptide vs protein: what is the difference?
The difference is mostly one of size and structure. Peptides are short and often lack the complex three-dimensional folding of a full protein. Proteins are longer chains (often hundreds or thousands of residues) that fold into stable shapes and frequently combine multiple chains.
Because peptides are smaller and simpler, they are widely used as reference standards and research tools in the laboratory: they can be synthesized to an exact sequence, characterized by mass spectrometry and HPLC, and studied in isolation.
How are research peptides made?
Most research peptides are produced by solid-phase peptide synthesis (SPPS). The chain is built one amino acid at a time on a solid resin support: each residue is coupled, the protecting group is removed, and the cycle repeats until the full sequence is assembled, after which the peptide is cleaved from the resin and purified.
The finished material is typically purified by reversed-phase HPLC and its identity confirmed by mass spectrometry. A Certificate of Analysis (COA) reports the measured purity and identity for a given batch — see our guide on how to read a COA.
The main families of research peptides
Research peptides are usually grouped by structure or by the pathway they are studied in. Common families include repair and cytoprotection reference peptides (such as BPC-157 and TB-500), growth-hormone-secretagogue reference compounds (the GHRH analogs and GHRP/ghrelin-receptor peptides such as CJC-1295, Ipamorelin, Sermorelin and the GHRPs), copper-binding peptides (GHK-Cu, AHK-Cu), the short "bioregulator" peptides (Epitalon, Thymalin and related Khavinson peptides), and regulatory/neuromodulation peptides (Semax, Selank).
Each compound on this site is a landing page that compares live vendor prices and cost per mg, with lot-independent identity data (CAS, molecular formula, sequence where published). Browse the full catalog by category to see how the families are organized.
Important: research use only
Everything discussed here is for laboratory research use only. Research peptides are reference materials and research tools — they are not drugs, supplements, or foods, and nothing on this site is intended for human or veterinary use, diagnosis, treatment, or consumption.