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Medical Term:


Pronunciation: lig'and, li'gand


  1. Any individual atom, group, or molecule attached to a central metal ion by multiple coordinate bonds, the porphyrin portion of heme, the corrin nucleus of the B12 vitamins.
  2. An organic molecule attached to a tracer element, a radioisotope.
  3. A molecule that binds to a macromolecule, a ligand binding to a receptor.
  4. The analyte in competitive binding assays, such as radioimmunoassay.
  5. An atom or group covalently attached to a specified carbon atom in an organic molecule.

[L. ligo, to bind]

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