Peptide research draws on chemistry, cell biology, and pharmacology, which means newcomers face a wall of unfamiliar terms. This glossary defines fifty essential concepts that appear regularly in peptide literature, organized for quick reference. Use it as a starting point when reading papers or reviewing technical documentation.
Chemistry and Handling Terms
Amino acid: The basic building block of peptides and proteins, joined by peptide bonds. Peptide bond: The covalent link between the carboxyl group of one amino acid and the amino group of another. Sequence: The order of amino acids in a peptide, typically written from N-terminus to C-terminus.
Lyophilization: Freeze-drying, used to stabilize peptides for storage. Reconstitution: Dissolving a lyophilized peptide in a solvent before use. Bacteriostatic water: Sterile water containing a preservative, used in some lab handling protocols. Acetate salt: A common counter-ion form for synthetic peptides.
Molecular weight: The mass of one peptide molecule, used in concentration calculations. Net charge: The overall charge on a peptide at a given pH. Isoelectric point (pI): The pH at which a peptide has zero net charge. Hydrophobicity: A measure of how strongly a peptide avoids water — relevant to solubility and membrane interaction.
Analytical Methods
HPLC: High-performance liquid chromatography, used to assess peptide purity. RP-HPLC: Reverse-phase HPLC, the most common variant for peptide analysis. Mass spectrometry (MS): A technique for confirming peptide identity by mass. LC-MS: Liquid chromatography combined with mass spectrometry.
Purity: The percentage of the sample that is the target peptide, usually reported by HPLC. Identity: Confirmation that the molecule is the expected sequence, usually by MS. Certificate of analysis (COA): A document reporting analytical results for a specific lot. Lot number: A unique identifier tying a sample to a specific production batch.
Endotoxin testing: Measurement of bacterial endotoxins in a sample. Residual solvents: Trace solvents left from synthesis. Counter-ion: The salt form a peptide is provided in (commonly acetate or trifluoroacetate). TFA: Trifluoroacetic acid, a common synthesis residue.
Biology and Signaling
Receptor: A protein that binds a specific molecule and triggers a cellular response. Agonist: A molecule that activates a receptor. Antagonist: A molecule that blocks a receptor. GPCR: G-protein coupled receptor, a major class of cell-surface receptors.
VEGF: Vascular endothelial growth factor, a signal that promotes blood vessel formation. EGF: Epidermal growth factor, involved in cell growth and differentiation. IGF-1: Insulin-like growth factor 1, involved in growth and metabolism. FAK: Focal adhesion kinase, central to cell migration signaling.
Phosphorylation: The addition of a phosphate group, often a regulatory switch on proteins. Cytokine: A small signaling protein involved in immune responses. Apoptosis: Programmed cell death. Angiogenesis: The formation of new blood vessels.
Pharmacology and Research Design
Pharmacokinetics (PK): How a compound is absorbed, distributed, metabolized, and excreted. Pharmacodynamics (PD): What the compound does to the body or system. Half-life: The time for half of a compound to be cleared. Bioavailability: The fraction that reaches systemic circulation in an active form.
In vitro: Performed in cells or test tubes. In vivo: Performed in living organisms. Ex vivo: Performed on tissue removed from an organism. Model organism: A species used to study biology that translates broadly.
Control group: A comparison group that does not receive the test compound. Vehicle: The solution used to deliver a compound, often included as a control. Dose-response: The relationship between amount and effect. EC50: The concentration producing half-maximal effect.
Sequestration: Binding and holding a molecule in reserve. Receptor desensitization: Reduced response after repeated activation. Downstream signaling: Events that follow initial receptor activation. Reproducibility: Whether independent labs can replicate results.
This list is a starting point — peptide research vocabulary continues to evolve as new techniques and pathways are characterized. All peptides discussed in research literature, including those referenced in glossary examples, are intended for laboratory research only — not for human consumption.