noun, plural: ligands
(1) A molecule, ion or atom bonded to the central metal atom of a coordination compound.
(2) Any substance (e.g. hormone, drug, functional group, etc.) that binds specifically and reversibly to another chemical entity to form a larger complex.
A ligand may function as agonist or antagonist.
Many ligands are found in biological systems, such as cofactors and porphyrin in hemoglobin.
Word origin: From Latin ligandus, gerundive of ligare ‘to bind’.
Related term: ligand gated ion channels