Peptide Glossary

Definitions of peptide science terms for European research laboratories.

Fundamentals

Amino acids: The building blocks of peptides and proteins. Each amino acid has an amino group, a carboxyl group, a central carbon, and a side chain (R group) that determines its chemical properties. Standard research peptides are assembled from L-amino acids in a defined sequence.
Bioactive peptide: A peptide that interacts with biological molecules such as receptors, enzymes, or ion channels in experimental models. “Bioactive” describes laboratory activity under study — not approved therapeutic use.
C-terminus: The end of a peptide chain that carries a free carboxyl group (–COOH). C-terminal modifications such as amidation are common in synthetic peptides to improve stability.
N-terminus: The end of a peptide chain that carries a free amino group (–NH2). Peptide sequences are written from N-terminus to C-terminus by convention.
Oligopeptide: A peptide consisting of a relatively small number of amino acids — typically fewer than 20 residues. Most catalogue research peptides are oligopeptides.
Peptide: A short chain of amino acids linked by peptide bonds. In research supply, “peptide” usually refers to synthetic sequences of roughly 2–50 residues used as laboratory reagents, distinct from full-length proteins.
Peptide analog: A synthetic variant of a naturally occurring peptide sequence, often with amino acid substitutions, extensions, or stabilising modifications to study structure–activity relationships in research.
Peptide bond: A covalent amide bond formed when the carboxyl group of one amino acid reacts with the amino group of the next, releasing water. Peptide bonds form the backbone of every peptide chain.
Polypeptide: A single linear chain of many amino acids joined by peptide bonds. Longer polypeptides may fold into functional structures; the term is often used interchangeably with “peptide” in laboratory contexts.
Primary structure: The linear order of amino acids in a peptide, from N- to C-terminus. Primary structure determines identity and underpins all higher-order folding and receptor interactions studied in vitro.

Synthesis & production

Acetylation: A common N-terminal modification that blocks the free amino group with an acetyl group. Acetylation can improve stability and mimic naturally processed peptide termini in research materials.
C-terminal amidation: Modification of the C-terminus to a carboxamide (–CONH2) instead of a free carboxyl acid. Often applied to synthetic peptides to reduce charge and improve stability in vitro.
Cleavage: The chemical step in SPPS that releases the completed peptide from the solid support resin. Cleavage conditions must be chosen carefully to minimise side reactions and preserve sensitive residues.
Disulfide bond: A covalent bond between two cysteine sulfur atoms that can stabilise peptide structure. Correct disulfide pairing is critical for peptides whose activity depends on folded conformation.
Lyophilisation: Freeze-drying that removes solvent from a peptide solution under vacuum, leaving a stable powder (“cake”) in the vial. Lyophilised peptides are the standard form supplied for research use.
Solid-phase peptide synthesis (SPPS): The standard method for producing research peptides. Amino acids are added sequentially to a peptide chain anchored on an insoluble resin, then cleaved and purified. SPPS allows precise control of sequence and batch consistency.

Analysis & quality

Certificate of Analysis (COA): Batch-specific documentation reporting identity, purity, appearance, and analytical results for a peptide lot. COAs allow laboratories to trace materials used in experiments and audit records. Browse products →
Deletion sequence: An impurity peptide missing one or more amino acids from the intended sequence, usually arising from incomplete coupling during synthesis. HPLC purity reporting captures these as non-target peaks.
HPLC: High-performance liquid chromatography — the primary analytical method for measuring peptide purity. Reverse-phase HPLC separates the target peptide from related impurities and reports purity as a percentage area under the main peak.
Independent testing (Janoshik): Third-party laboratory verification of selected batches using HPLC and mass spectrometry. Peptides EU publishes Janoshik Analytical reports for certain compounds so researchers can review independent data alongside batch COAs.
Mass spectrometry (MS): An analytical technique that measures molecular mass and confirms peptide identity. LC-MS combines chromatography with mass detection for sequence verification and impurity profiling.
Net peptide content: The actual mass of the target peptide in a vial, as distinct from total lyophilised mass which may include counter-ions, residual moisture, or excipients. COAs and product labels state the nominal peptide quantity per vial.
Purity: The proportion of the target peptide relative to other peptide-related peaks detected by HPLC. Research-grade peptides are typically supplied at ≥99% purity unless otherwise stated on the COA.

Handling & storage

Acetic acid solution: A dilute acidic diluent used for peptides with poor solubility at neutral pH. Product pages and COAs indicate when an acidic reconstitution solvent is recommended.
Aliquot: A small, measured portion of reconstituted peptide solution stored separately. Aliquoting reduces freeze–thaw cycles and helps preserve peptide integrity during long experiments.
Bacteriostatic water: Sterile water containing 0.9% benzyl alcohol as a preservative. Commonly used to reconstitute research peptides when multiple aliquots will be drawn from the same container over time. Lab supplies →
Freeze–thaw cycle: Repeated freezing and thawing of a peptide solution, which can accelerate degradation or aggregation. Minimise cycles by aliquoting at reconstitution.
In vitro: Experiments conducted outside a living organism — for example in cell culture, binding assays, or biochemical preparations. All Peptides EU products are supplied exclusively for in vitro and laboratory research. Research disclaimer →
Reconstitution: Dissolving lyophilised peptide powder in a suitable diluent (such as bacteriostatic water) to prepare a working solution for in vitro experiments. Volume and concentration should be planned before opening the vial. Reconstitution guide →
Research use only (RUO): A designation indicating that materials are sold strictly for laboratory research and are not intended for human consumption, veterinary therapeutic use, or clinical application.

Common research compounds

BPC-157: A synthetic pentadecapeptide derived from body protection compound (BPC) sequences, widely used in in vitro models studying tissue repair pathways, angiogenesis, and inflammatory signalling. View catalogue →
CJC-1295: A GHRH analog peptide available with or without drug affinity complex (DAC). Research applications focus on GHRH receptor pharmacology and related signalling cascades in controlled laboratory models. View catalogue →
Epitalon: A synthetic tetrapeptide (Ala-Glu-Asp-Gly) studied in telomerase activity and cellular senescence models. A common compound in longevity-related in vitro research. View catalogue →
GHK-Cu: A copper-binding tripeptide (glycyl-L-histidyl-L-lysine) studied in extracellular matrix, gene expression, and oxidative stress models. Supplied lyophilised and reconstituted according to laboratory SOPs. View catalogue →
Ipamorelin: A selective growth hormone secretagogue receptor agonist peptide used in receptor binding and signalling pathway research. Often studied alongside GHRH analogues in vitro. View catalogue →
Melanotan peptides: Synthetic melanocortin analog peptides (including Melanotan I and II sequences) studied for melanocortin receptor binding and pigmentation pathway research in vitro. View catalogue →
PT-141: A cyclic melanocortin receptor agonist peptide (bremelanotide sequence) used in receptor pharmacology and binding studies in laboratory research. View catalogue →
Semaglutide: A GLP-1 receptor agonist peptide analog studied in metabolic and receptor pharmacology research. Supplied for in vitro laboratory use only — not for therapeutic application. View catalogue →
TB-500: A research peptide corresponding to a fragment of thymosin beta-4, commonly studied in cell migration and cytoskeletal organisation assays in laboratory settings. View catalogue →
Tirzepatide: A dual GIP/GLP-1 receptor agonist peptide analog used in biochemical and cell-based research exploring incretin pathway signalling. View catalogue →

Cellular & molecular

Cytokine: A signalling protein involved in immune and inflammatory responses. Some research peptides are studied for their effects on cytokine expression or secretion in vitro.
Endoplasmic reticulum (ER): A membrane network involved in protein folding and lipid synthesis. Peptide handling in cells and secretion pathways are studied in ER-related laboratory models.
Ligand: A molecule — including research peptides — that binds to a receptor or other target protein. Ligand–receptor studies are a core application of catalogue peptides in cell biology.
Mitochondria: Cellular organelles responsible for energy production. Mitochondrial-targeted peptides (such as SS-31 analogs) are studied in oxidative stress and bioenergetics research models.
Neuropeptide: A peptide that acts as a signalling molecule in the nervous system. Many research peptides mimic or modulate neuropeptide pathways in cell culture and binding assays.
Receptor: A protein, often on the cell surface, that binds specific ligands such as peptide hormones and triggers intracellular signalling. Peptide research frequently examines receptor binding affinity and downstream pathways.
Ribosome: The cellular machinery that assembles proteins from amino acids on mRNA templates. Synthetic research peptides bypass ribosomal synthesis but are studied in systems that interact with ribosome-derived proteins.
Signal peptide: A short amino acid sequence that directs proteins to specific cellular compartments during synthesis. Distinct from “signalling peptides” used as laboratory reagents.

Need practical guidance?

Explore our reconstitution guide, peptide calculator, and FAQ for handling and ordering questions.

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All products are for in vitro laboratory research only. Not for human or veterinary use.