Glossary Research peptides: essential terms from A to Z

A

Amino acid An organic molecule containing an amine group (-NH2) and a carboxyl group (-COOH). The 20 proteinogenic amino acids are the building blocks of peptides and proteins.

Agonist : A molecule that binds to a receptor and activates its biological response. An agonist peptide mimics the action of the natural ligand (e.g., Ipamorelin is an agonist of the GHS-R1a receptor).

Similar A compound structurally similar to a natural molecule but modified to improve certain properties (stability, selectivity, potency). Example: Semaglutide is an analog of native GLP-1.

Angiogenesis : Formation of new blood vessels from pre-existing vessels. Key process in tissue healing (BPC-157 stimulates local angiogenesis via VEGF).

B

BAC (bacteriostatic water) Sterile water containing 0.9% benzyl alcohol as an antimicrobial agent. Used to reconstitute lyophilized peptides while preventing bacterial contamination.

BDNF (Brain-Derived Neurotrophic Factor) : A crucial neurotrophic factor for neuronal survival, synaptic plasticity, and memory. A target modulated by Selank and Semax.

Bioavailability : Fraction of an administered compound that reaches systemic circulation in active form. Peptides injected subcutaneously generally have a bioavailability close to 100%.

BPC (Body Protection Compound) : Natural protein found in human gastric juice. BPC-157 is a synthetic fragment of 15 amino acids derived from this protein.

C

COA (Certificate of Analysis) Document issued by an analytical laboratory certifying the purity, identity, and quality of a peptide batch. Must include HPLC and MS results at a minimum.

Cyclic (peptide) : A peptide whose ends or side chains are linked to form a ring. Cyclization increases stability and can improve selectivity (e.g., PT-141 is a cyclic peptide).

D

DAC (Drug Affinity Complex) Chemical modification (addition of a lysine fatty acid) that allows reversible binding to serum albumin, considerably prolonging the half-life. Used in CJC-1295 DAC.

Half-life (t1/2) Time required for the plasma concentration of a compound to decrease by half. Determines the frequency of administration in research.

Dimer : Aggregate of two peptide molecules. Dimerization is a form of degradation that reduces biological activity. This is prevented by proper storage (cold storage, absence of freeze/thaw cycles).

E

EC50 Median effective concentration — the concentration of a compound needed to produce 50% of its maximum effect. A measure of the potency of an agonist.

eNOS (endothelial Nitric Oxide Synthase) : Enzyme producing nitric oxide (NO) in endothelial cells. Primary target of BPC-157 for its vascular and wound-healing effects.

G

GH (Growth Hormone) Growth hormone, secreted by the anterior pituitary gland. GH secretagogues (Ipamorelin, GHRP-6) stimulate its natural pulsatile release.

GHS-R1a : Growth Hormone Secretagogue Receptor type 1a. Ghrelin receptor, target of secretagogue peptides such as Ipamorelin and GHRP-2.

GHRH (Growth Hormone Releasing Hormone) GHRH is a hypothalamic hormone that stimulates the synthesis and secretion of GH. CJC-1295 and Tesamorelin are GHRH analogues.

GLP-1 (Glucagon-Like Peptide-1) Intestinal incretin that regulates blood sugar and satiety. Semaglutide and Tirzepatide are GLP-1 receptor agonists.

H

HPLC (High-Performance Liquid Chromatography) HPLC is the reference analytical technique for determining peptide purity. It separates the components of a mixture by affinity with a stationary phase. HPLC purity of 99%+ is the quality standard for research.

Hydrolysis : Cleavage of a chemical bond by water. Peptide bonds are hydrolyzed by proteases, which constitutes the main pathway of peptide degradation in vivo.

I

IGF-1 (Insulin-like Growth Factor 1) Growth factor produced mainly by the liver in response to GH. Mediator of many anabolic effects of the GH/IGF-1 axis.

IC50 : Median inhibitory concentration — the concentration required to inhibit 50% of the activity of a target. Used to characterize antagonists and inhibitors.

L

Freeze-drying Sublimation drying process (freezing followed by evaporation under vacuum). Lyophilized peptides are stable at room temperature for months and require reconstitution before use.

Peptide bond : Covalent amide bond (-CO-NH-) between the carboxyl group of one amino acid and the amine group of the next. Forms the backbone of every peptide.

M

MS (Mass Spectrometry) Analytical technique measuring the mass-to-charge ratio of molecules. Confirms the identity of a peptide by its exact molecular mass. Essential complement to HPLC in a COA.

MC4R (Melanocortin 4 Receptor) : Hypothalamic receptor of the melanocortin system, involved in the regulation of appetite and behavior. Target of PT-141 and Retatrutide.

N

NO (Nitric Oxide) Vasodilator gas and second messenger produced by NOS. Involved in angiogenesis, wound healing, and endothelial protection. Key pathway of BPC-157.

Nootropic A compound that enhances cognitive functions (memory, attention, learning) without significant toxicity. Selank and Semax are nootropic peptides.

P

Pentapeptide A peptide composed of 5 amino acids (e.g., Ipamorelin). Oligopeptides (2-20 AA) are distinguished from polypeptides (20-50 AA) and proteins (50+ AA).

Pulsatility GH secretion occurs in pulses (peaks) rather than continuously. GH is secreted in a pulsatile manner; secretagogues respect this physiological pattern, unlike exogenous GH.

R

Reconstruction Dissolving a lyophilized peptide (powder) in a solvent (bacteriostatic water or sterile water). This must be done carefully by letting the solvent flow down the side of the bottle.

Receiver A protein (membrane or intracellular) that specifically recognizes a ligand and triggers a cellular response. Each research peptide targets one or more specific receptors.

S

SC (subcutaneous) Route of injection into subcutaneous adipose tissue. Standard route for most research peptides, offering slow and steady absorption.

Secretagogue : A substance that stimulates the secretion of a hormone. GH secretagogues (Ipamorelin, GHRP-2) trigger the release of endogenous GH by the pituitary gland.

Sequence Linear order of amino acids in a peptide, written from the N-terminal end (amine) to the C-terminal end (carboxyl). Determines the 3D structure and biological function.

T

Tmax Time required to reach maximum plasma concentration after administration. For SC peptides, Tmax is generally 15 to 60 minutes.

TrkB : Tyrosine kinase B receptor, the main receptor for BDNF. Its activation triggers neuronal survival and synaptic plasticity pathways (PI3K/Akt, MAPK/ERK).

V

VEGF (Vascular Endothelial Growth Factor) : Vascular growth factor that stimulates angiogenesis. Produced in response to BPC-157, hypoxia, and wound healing signals.

Signaling lane : Cascade of intracellular biochemical reactions triggered by the activation of a receptor. Ex: GHS-R1a → Gq → PLC → IP3 → Ca2+ → GH release.