Plain-English definitions of key terms in peptide science.
The building blocks of peptides and proteins. There are 20 standard amino acids, each with a unique side chain that determines its chemical properties. They link together via peptide bonds to form chains.
The fraction of an administered compound that reaches the bloodstream in its active form. Injectable peptides typically have high bioavailability; oral peptides often have very low bioavailability due to digestive breakdown.
A short peptide (typically 2–4 amino acids) theorized to regulate gene expression in specific tissues. The concept was developed by Professor Vladimir Khavinson at the St. Petersburg Institute of Bioregulation and Gerontology.
A document that accompanies research peptides reporting the results of quality testing, including purity (via HPLC), identity (via mass spectrometry), and sometimes endotoxin or residual solvent levels.
A peptide whose amino acid chain forms a ring structure, often through a disulfide bond between cysteine residues. Cyclic peptides tend to be more stable and resistant to enzymatic degradation than linear peptides.
A unit of molecular mass equal to approximately the mass of one hydrogen atom. Peptide molecular weights are typically measured in Daltons. A kilodalton (kDa) equals 1,000 Daltons.
A peptide consisting of exactly two amino acids linked by one peptide bond. The simplest possible peptide.
Produced naturally within the body. An endogenous peptide is one that your cells manufacture themselves, as opposed to a synthetic (lab-made) version.
A type of small extracellular vesicle (30–150 nanometers) released by cells. Exosomes carry cargo — proteins, RNA, lipids — from one cell to another, acting as intercellular communication vehicles.
A hormone produced by cells in the gut after eating. It signals the pancreas to release insulin, slows gastric emptying, and signals fullness to the brain. GLP-1 receptor agonists like semaglutide mimic this hormone.
A naturally occurring signaling molecule (usually a protein or peptide) that stimulates cell growth, proliferation, healing, and differentiation. Examples include EGF, FGF, and VEGF.
The time it takes for half of a substance to be eliminated from the body or lose its biological activity. Short half-life peptides need more frequent administration; long half-life peptides (like semaglutide) can be given weekly.
An analytical technique used to separate, identify, and quantify components in a mixture. In peptide research, HPLC is the gold standard for measuring purity — a 98%+ purity means the sample is almost entirely the intended peptide.
Freeze-drying — a preservation process that removes water from a frozen peptide solution under vacuum. The result is a dry, stable powder (lyophilized cake) that can be stored long-term and reconstituted before use.
An analytical technique that measures the mass-to-charge ratio of ions. In peptide research, it is used to confirm molecular identity by comparing the measured mass to the expected molecular weight.
The specific biochemical process through which a molecule produces its biological effect. Understanding MOA helps researchers predict effects, interactions, and potential research applications.
A peptide that functions as a neurotransmitter or neuromodulator in the nervous system. Neuropeptides influence brain function, mood, pain perception, sleep, and many other neurological processes.
A short peptide consisting of 2–20 amino acid residues. The term encompasses dipeptides, tripeptides, tetrapeptides, and other short chains.
A short chain of amino acids linked by peptide bonds. Generally defined as 2–50 amino acids long (longer chains are called proteins). Peptides can act as hormones, neurotransmitters, growth factors, and signaling molecules.
The chemical bond that joins two amino acids together. It forms between the carboxyl group (-COOH) of one amino acid and the amino group (-NH₂) of the next, releasing a water molecule in the process.
A longer chain of amino acids (typically 20–50+). The boundary between peptide and polypeptide is not strict. Polypeptides bridge the gap between short peptides and full proteins.
A regulatory designation meaning a compound is intended exclusively for laboratory research and is not approved for human or animal use, diagnosis, or treatment.
The specific order of amino acids in a peptide chain, read from the N-terminus (start) to the C-terminus (end). The sequence determines the peptide's structure, function, and biological activity.
An injection method where the needle is inserted into the fatty tissue just beneath the skin. This is the most common injection route studied for research peptides.
The protective cap at the end of each chromosome, made of repetitive DNA sequences. Telomeres shorten with each cell division. When they become too short, the cell can no longer divide properly.
An enzyme that adds telomere sequences back to chromosome ends, counteracting telomere shortening. Most adult cells have very low telomerase activity. Some peptides (like Epithalon) are studied for their potential effects on telomerase.
A peptide consisting of exactly three amino acids. Many bioregulator peptides are tripeptides, and the small size may allow unique cellular interactions.