Chelation
From Free net encyclopedia
Chelation (from Greek χηλή, chelè, meaning claw) is the process of reversible binding of a ligand, the chelant, chelator or chelating agent, to a metal ion, forming a metal complex, the chelate.
Image:Metal-EDTA.png Chelators are used in chemical analysis, as water softeners, as preservatives, and in medicine (chelation therapy), where they are employed to safely bind with poisonous metal agents such as mercury, arsenic, or lead in order to stabilize them and allow them to be excreted without further interaction with the body. Natural chelators include the porphyrin rings in hemoglobin or chlorophyll and the Fe3+ chelating siderophores secreted by microorganisms, and are contained in herbs such as cilantro, which has long been used as a treatment for heavy metal poisoning. A commonly used synthetic chelator is EDTA.
A chelator does not have to be organic. In contrast to the simple monodentate ligands like H2O or NH3, which are easily broken apart by other chemical processes, the polydentate chelators form multiple bonds with the metal ion, resulting in more stable complexes.
Metal complexes are of widespread interest and studied by inorganic chemists, physical and organic chemists, biochemists, pharmacologists, molecular biologists, and environmentalists.
Antibiotic drugs of the tetracycline family are also chelators of Ca2+ and Mg2+ ions and are incorporated into bones and teeth.
In ecology chelation compounds are related to the mobilization of metals in the soil, the uptake and the accumulation of metals into plants and micro-organisms and as a mechanism for resistance and hyperaccumulation adaptations. Such chelation of heavy metals can be used in bioremediation.Template:Ref
The term chelate was first applied in 1920 by Sir Gilbert T. Morgan and H. D. K. Drew in J. Chem. Soc., 1920, 117, 1456, who stated: "The adjective chelate, derived from the great claw or chele (Greek) of the lobster or other crustaceans, is suggested for the caliperlike groups which function as two associating units and fasten to the central atom so as to produce heterocyclic rings."
See also
de:Chelatligand es:Ligando quelato fr:Chélation io:Kel-ionuro ja:キレート zh:螯合物
References cited
- Template:Note Prasad (ed). Metals in the Environment. University of Hyderabad. Dekker, New York, 2001