Peptide Research Glossary
Plain definitions for the terms used throughout this site.
Last reviewed September 1, 2026
Terms
Agonist — a molecule that activates a receptor. Antagonist — one that blocks it.
Analogue — a modified version of a natural molecule, usually altered to last longer or bind more selectively.
Bacteriostatic water — sterile water containing a preservative, used as a diluent where a vial will be accessed repeatedly.
COA — certificate of analysis, a laboratory report on a specific batch.
Half-life — the time for the amount of a compound in circulation to fall by half.
In-vitro — in cells or tissue outside a living organism. In-vivo — in a living organism.
Lyophilised — freeze-dried to a dry powder for stability.
Net peptide content — the proportion of a vial's mass that is the peptide itself, as distinct from salts and water.
Pharmacokinetics — what the body does to a compound. Pharmacodynamics — what the compound does to the body.
Randomised controlled trial — participants assigned by chance to treatment or control, the strongest common study design.
Reconstitution — adding diluent to a lyophilised powder to return it to solution.
RUO — research use only.
Surrogate endpoint — a measurement used as a stand-in for an outcome that matters, such as a biomarker in place of a health event.