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Browse CatalogWorking with peptides involves a lot of specialized terminology. Whether you are new to peptide research or just need a quick refresher, this glossary covers the most commonly used terms in peptide science, synthesis, analysis, and handling. Where applicable, we have linked to our more detailed guide pages for further reading.
Acetylation: The addition of an acetyl group (CH3CO) to the N-terminus of a peptide. N-terminal acetylation is a common modification that protects the peptide from aminopeptidase degradation and eliminates the positive charge at the N-terminus.
Aggregation: The process by which peptide molecules clump together, forming soluble oligomers or insoluble precipitates. Aggregation is often driven by hydrophobic interactions and can reduce biological activity. See our Peptide Stability guide.
Amidation: The modification of the C-terminus of a peptide to replace the carboxyl group with an amide group (CONH2). C-terminal amidation is frequently used because many naturally occurring peptides are amidated, and it can improve biological activity and stability.
Amino Acid: The building blocks of peptides and proteins. There are 20 standard amino acids encoded by the genetic code, each with a unique side chain that determines its chemical properties.
Amino Acid Analysis (AAA): An analytical technique that determines the amino acid composition of a peptide by breaking it into individual amino acids and quantifying each one. See our AAA guide.
Bacteriostatic Water (BAC Water): Sterile water containing 0.9% benzyl alcohol as a preservative. Commonly used for reconstituting lyophilized peptides. See our Solvent Selection Guide.
Bioavailability: The proportion of a substance that enters circulation and is available to produce an active effect.
Biotinylation: The attachment of a biotin molecule to a peptide. Biotinylated peptides can be detected using streptavidin, making this useful for binding assays and pull-down experiments.
Certificate of Analysis (COA): A quality control document reporting analytical testing results for a specific peptide batch. See Understanding Your COA.
Cold Chain: A temperature-controlled supply chain used to maintain product integrity during shipping. See our Shipping Information page.
Coupling: In solid-phase peptide synthesis, the chemical reaction that forms a peptide bond between two amino acids.
Crude Peptide: The raw product of peptide synthesis before purification. Contains the target peptide along with impurities.
Cyclization: The formation of a ring structure in a peptide through disulfide bonds, lactam bridges, or head-to-tail cyclization.
D-Amino Acid: The mirror image (enantiomer) of a standard L-amino acid. Incorporation of D-amino acids can confer resistance to proteolytic degradation.
Deamidation: A common degradation reaction in which asparagine is converted to aspartate. See Peptide Stability.
Deletion Sequence: An impurity where one or more amino acid residues are missing from the sequence.
Desiccant: A drying agent used to absorb moisture during peptide storage. See our Storage Guide.
DMSO (Dimethyl Sulfoxide): A powerful organic solvent used to dissolve hydrophobic peptides. See Solvent Selection Guide.
Electrospray Ionization (ESI): A mass spectrometry ionization method producing multiply charged ions. See our Mass Spectrometry guide.
Epitope: The specific part of an antigen recognized by an antibody.
Fmoc (Fluorenylmethyloxycarbonyl): A protecting group used in modern solid-phase peptide synthesis. The industry standard for peptide manufacturing.
Freeze-Drying: See Lyophilization.
HPLC (High-Performance Liquid Chromatography): The primary analytical and purification method for peptides. See our HPLC guide.
Hydrolysis: The cleavage of a chemical bond by water. Peptide bonds can undergo hydrolysis at extreme pH or elevated temperature.
Hydrophobic: Water-repelling. Amino acids like Ala, Val, Leu, Ile, Phe, Trp, and Pro have hydrophobic side chains.
Lyophilization (Freeze-Drying): The process of removing water from a frozen sample by sublimation under vacuum. Lyophilized peptides are more stable than solutions.
MALDI (Matrix-Assisted Laser Desorption/Ionization): A mass spectrometry ionization technique using a laser. See Mass Spectrometry guide.
Molecular Weight (MW): The sum of the atomic weights of all atoms in a molecule.
m/z (Mass-to-Charge Ratio): The value measured by a mass spectrometer.
Net Peptide Content: The actual amount of active peptide in a sample, expressed as a percentage of total weight. Determined by amino acid analysis.
Oxidation: A common degradation pathway for methionine, cysteine, and tryptophan residues. See Peptide Stability.
PEGylation: The attachment of polyethylene glycol (PEG) chains to a peptide to improve solubility and extend half-life.
Peptide Bond: The covalent bond between the carboxyl group of one amino acid and the amino group of another.
Phosphorylation: The addition of a phosphate group to serine, threonine, or tyrosine residues.
Reconstitution: The process of dissolving a lyophilized peptide in solvent. See our Reconstitution Guide.
Reversed-Phase (RP): A chromatographic mode where the stationary phase is hydrophobic. The standard method for peptide HPLC.
Solid-Phase Peptide Synthesis (SPPS): The standard method for manufacturing synthetic peptides.
Solubility: The ability of a peptide to dissolve in a given solvent. See Solvent Selection Guide.
TFA (Trifluoroacetic Acid): A common counter-ion in synthetic peptides and a mobile phase additive in HPLC.
For detailed information, explore our Research Guides Hub. Questions? Email support@nxpeptides.com or visit the Contact page.
All NXPeptides products are for research use only. Not for human consumption.