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ligand

ligand (lĬg´ənd), charged or uncharged molecule with one or more unshared pairs of electrons that can attach to a central metallic atom or ion to form an aggregate known as a complex ion (see chemical bond). Some ligands that share electrons with metals form very stable complexes. Some common bases that act as ligands are water and ammonia molecules and halide, hydroxide, acetate, cyanide, thiocyanate, and nitrite anions. These ligands are monofunctional, i.e., they are attached by one unshared pair of electrons during complexing. Polyfunctional ligands, which bind to the metal ion with two or more pairs of electrons, are called chelates (see chelating agents). Ethylenediamine-tetraacetate, a commonly used chelating compound, has six pairs of electrons to bind to metal ions. Electron-donating functional groups containing nitrogen, oxygen, sulfur, phosphorous, or carbon may act as ligands in complex biological systems. For example, in enzymes that need complexed metal ions to function, mercapto (sulfur-containing) groups and amino (nitrogen-containing) groups act as chelating agents; these groups fix the metal ion in a specific position. Other biologically important molecules, such as chlorophyll, vitamin B12, and heme, also have nitrogen-containing groups that donate electrons and have a chelating function.

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ligand

ligand
1. (in chemistry) An ion, atom, or molecule that donates a pair of electrons to a metal atom to form a type of covalent bond called a coordinate bond.

2. (in cell biology) A molecule that binds to a protein with a high degree of specificity. Examples are the substrate of an enzyme and a hormone binding to a cell receptor.

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ligand

ligand
1. An atom, ion, or molecule that acts as the electron-donor partner in one or more co-ordination bonds. A heterocyclic ring is formed if the ligand is an organic compound, and the product is termed a chelate.

2. A molecule (e.g. an antibody) that can bind to specific sites on cell membranes.

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ligand

ligand Atom, ion, or molecule that acts as the electron-donor partner in one or more coordination bonds. A heterocyclic ring is formed if the ligand is an organic compound, and the product is termed a chelate. See also CHELATION; and COORDINATION NUMBER.

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ligand

ligand An atom, ion, or molecule that acts as the electron-donor partner in one or more co-ordination bonds. A hetero-cyclic ring is formed if the ligand is an organic compound, and the product is termed a chelate.

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ligand

ligand (lig-ănd) n. a molecule that binds to another molecule, as in antigen–antibody and hormone–receptor bondings.

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ligand

ligandunironed, viand •prebend •beribboned, riband •husband • house husband •unquestioned • escutcheoned •brigand, ligand •legend •fecund, second, split-second •millisecond • nanosecond •microsecond • rubicund • jocund •Langland • garland • parkland •Cartland, heartland •headland • Shetland • Lakeland •mainland •eland, Leland, Wieland, Zealand, Zeeland •Greenland • heathland • Cleveland •Friesland • Queensland • midland •England • Finland • Maryland •dryland, highland, island •Iceland • Holland • dockland •Scotland •foreland, Westmorland •Auckland, Falkland •Portland • Northland •lowland, Poland, Roland •Oakland • Copland • Newfoundland •woodland • Buckland • upland •Jutland, Rutland •Ireland • moorland •Cumberland, Northumberland •Sunderland • Switzerland •Sutherland • Hammond •almond, Armand •Edmund, Redmond •Desmond, Esmond •Raymond • Grimond • Richmond •Sigmund • Sigismund • Osmond •Dortmund • unsummoned •diamond • gourmand • unopened •errand, gerund •reverend • Bertrand • dachshund •unchastened •old-fashioned, unimpassioned •unsanctioned •aforementioned, undermentioned, unmentioned •unconditioned • unsweetened •unenlightened • unleavened •self-governed • unseasoned •wizened • thousand

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