Research Terminology

Half-life is the time taken for the concentration of a compound in plasma to fall by half. It determines dosing intervals, but it does not always predict duration of effect — some peptides accumulate in tissue and act well after plasma levels fall.

Bioavailability is the proportion of an administered amount that reaches systemic circulation. Subcutaneous administration typically gives high bioavailability for peptides; oral administration usually gives very low bioavailability because of digestive breakdown.

An agonist binds a receptor and activates it. An antagonist binds and blocks it. A partial agonist activates it incompletely. A dual or triple agonist activates two or three distinct receptor types with a single molecule.

An analogue is a modified version of a natural molecule. A fragment is a portion of a larger natural sequence. Both terms appear constantly in peptide names and each implies a different relationship to the parent compound.

Lyophilised means freeze-dried. Reconstituted means returned to solution. Bacteriostatic refers to a solvent containing a preservative that inhibits bacterial growth.

Purity figures such as 'greater than 98% by HPLC' describe the proportion of the material that is the intended sequence, as measured by high-performance liquid chromatography. A certificate of analysis documents this and the mass spectrometry identity check.

In vitro means in cell culture or a test tube. In vivo means in a living organism. Preclinical describes work conducted before human studies begin.

A randomised controlled trial assigns participants to groups by chance. Double-blind means neither participants nor investigators know group assignment. Placebo-controlled means one group receives an inactive comparator.