High Quality Content by WIKIPEDIA articles! A pharmacophore is an abstract description of molecular features which are necessary for molecular recognition of a ligand by a biological macromolecule. The IUPAC defines a pharmacophore to be "an ensemble of steric and electronic features that is necessary to ensure the optimal supramolecular interactions with a specific biological target and to trigger (or block) its biological response". In simple English, a pharmacophore is the portion of a ligand molecule which binds to the receptor site. The pharmacophore of a ligand may be localised in a particular area of the ligand molecule or it may be spread across different areas of the ligand molecule. An example of this is the neuromuscular blocking agent, tubocurarine. The quaternary nitrogens present in the tubocurarine molecule are believed to make up its pharmacophore.