The simple definition
A peptide is a short chain of amino acids — typically between two and around fifty residues — joined by covalent peptide bonds. Anything longer than roughly fifty amino acids is generally classified as a protein, though the cut-off is conventional rather than absolute. Every peptide has a defined sequence, a defined molecular weight and (once folded) a defined three-dimensional shape that determines how it interacts with receptors and enzymes.
Peptides vs proteins vs amino acids
Amino acids are the individual building blocks. Peptides are short assembled chains. Proteins are long, often folded chains made of one or more peptide subunits. The same twenty proteinogenic amino acids can produce billions of distinct peptide sequences — which is why peptides are such a rich target for research.
The main peptide categories
Research peptides are usually grouped by function: signalling peptides (e.g. GLP-1 analogues such as semaglutide and tirzepatide), regenerative peptides (e.g. BPC-157, TB-500), growth-hormone-related peptides (e.g. CJC-1295, Ipamorelin), cosmetic peptides (e.g. GHK-Cu), and mitochondrial peptides (e.g. SS-31, MOTS-c). Each category has its own literature and its own handling profile.
How peptides are made
Modern research peptides are produced by solid-phase peptide synthesis (SPPS), where the chain is built one amino acid at a time on a solid resin. The crude product is then purified, most commonly by reversed-phase HPLC, and verified by mass spectrometry. Quality grade is defined by purity (HPLC %), identity (mass-spec confirmation) and peptide content.
Why purity matters
Two vials labelled the same peptide can behave very differently if one contains truncated sequences, salt or process residues. Research-grade peptides should always ship with a lot-matched Certificate of Analysis (COA) showing HPLC purity, mass-spec identity and peptide content. Anything below 98–99% HPLC purity introduces real variability into experimental results.
Where to go next
If you are evaluating a specific compound, the Peptide Library lists every Regena peptide with its COA. For a deeper conceptual primer, the research-compound basics page covers handling, storage and reconstitution in more detail.
Frequently asked questions
What are peptides in simple terms?+
Peptides are short chains of amino acids — the same building blocks that make up proteins, just in a shorter chain. They are studied because many of them act as precise biological signals.
Are peptides the same as proteins?+
No. Peptides are short chains (typically under fifty amino acids). Proteins are longer chains, often folded into complex structures. Every protein is built from one or more peptides, but not every peptide is a protein.
What are peptides used for in research?+
Research uses span metabolism (GLP-1 analogues), tissue regeneration (BPC-157, TB-500), growth-hormone pathways, mitochondrial biology and dermatological models. Every use here is in-vitro / laboratory only.
Is peptide content the same as purity?+
No. HPLC purity tells you the proportion of the target sequence in the peptide fraction; peptide content tells you how much of the vial mass is actually peptide versus counter-ions, water and salt. Both matter.
Continue your research
What is a peptide?
What is peptide therapy?
Are peptides safe?
How to reconstitute peptides
Peptide Library
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Lab reports & COAs
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Research compounds overview
Laboratory peptides guide
Storage & reconstitution guide
Peptide glossary