What is the difference between a peptide and a protein?
There is no strict scientific boundary, but peptides are conventionally shorter chains (typically 2–50 amino acids), while proteins are larger and usually fold into complex three-dimensional structures. Some sources use 50 amino acids as a rough cutoff.
Are therapeutic peptides the same as research peptides?
Therapeutic peptides are approved drugs (e.g., insulin, semaglutide) that have gone through rigorous clinical testing. Many research peptides sold for laboratory use have not been evaluated for human safety or efficacy and are not intended for therapeutic use.
Why are many peptides unstable or have short half-lives?
Peptides are susceptible to rapid degradation by proteases in the body. They are also often cleared quickly by the kidneys. Researchers improve stability through cyclization, D-amino acids, N- or C-terminal modifications, and PEGylation.
Can peptides be taken orally?
Most peptides have very poor oral bioavailability because they are broken down in the digestive tract. Notable exceptions include some cyclic peptides (e.g., cyclosporin) and newer formulations using permeation enhancers or lipidation (such as oral semaglutide).
What does 'research use only' mean for peptide products?
It indicates the material is intended strictly for laboratory experiments and is not manufactured or tested to pharmaceutical standards. It should not be used in humans or animals for therapeutic purposes. Regulatory agencies may still treat marketed injectable products as unapproved drugs regardless of labeling.
What is BPC-157?
BPC-157 is a synthetic 15-amino-acid peptide studied in preclinical models of tissue repair and gastrointestinal protection. It is not an approved therapeutic in Canada or the United States. See our full educational profile for chemistry and research context.
What is TB-500?
TB-500 usually refers to a synthetic fragment associated with thymosin beta-4 research, studied in experimental models of cell migration and tissue remodeling. It is not an approved medicine. See the TB-500 profile for details.
How are peptides different from small-molecule drugs?
Peptides are larger, more specific in their interactions, and generally mimic natural biological signals. Small molecules can be more easily taken orally and often cross cell membranes better, but peptides can target protein-protein interactions that are difficult for small molecules to address.
What is solid-phase peptide synthesis?
A method in which amino acids are added sequentially to a growing chain attached to an insoluble resin bead. It allows automated, high-yield production of custom sequences and is the most common laboratory technique.
Do all peptides have biological activity?
No. While many peptides are signaling molecules, structural fragments, or enzyme substrates, others may be inactive or serve primarily structural roles. Activity depends on sequence, structure, and the biological context.
What are common modifications used in research peptides?
Acetylation or amidation of termini, cyclization (head-to-tail or disulfide), incorporation of D-amino acids, fluorescent labels, biotin tags, PEGylation, and lipidation are frequently used to alter stability, solubility, or detection.
Are antimicrobial peptides being developed as new antibiotics?
Yes. Because of rising antibiotic resistance, many research groups are studying naturally occurring and synthetic antimicrobial peptides. Challenges include toxicity to host cells, stability, and production cost.
How do researchers study peptide-receptor interactions?
Common methods include binding assays, surface plasmon resonance (SPR), isothermal titration calorimetry (ITC), NMR, X-ray crystallography, and cellular functional assays measuring downstream signaling.
Is there a database of all known peptides?
Several specialized databases exist, including the Antimicrobial Peptide Database (APD), PeptideAtlas (mass spec identifications), and UniProt (which includes many peptide sequences). No single database contains every possible peptide.
Still have questions? Read the peptide encyclopedia, check the Glossary, or explore Resources.