Chelator Function and Structure
Chelators or chelating agents are small water-soluble molecules which form complexes with metal ions and are occasionally fluorescent. As a complex (chelate) they are inert in solution; requiring high energy for dissociation. However, metal exchange is possible in labile complexes. Sequestering agents represent chelators which produce soluble metal complexes.
The functional groups of chelators are two of =O, -NH2 or -COO-. These are groups which donate an electron pair to the metal ion to form the complex and must be positioned correctly to allow ring formation. Chelators represent a major component of cellular metabolism.
Popular chelators include EDTA and Deferoxamine Mesylate.
Natural Chelators (can aid in physiological systems transport iron and oxygen) include:
• Ionophores (monensin, valinomycin, gramicidin)
Synthetic Chelators (suitable for separating metals in solutions) include:
• ionophores Nitrilotriacetic acid, NTA ortho-Phenanthroline
• Salicylic acid
• Triethanolamine, TEA
• Ethylene glycol-bis-(2-aminoethyl)-N,N,N', N'-tetraacetic acid (EGTA)
• Ethylenediaminotetraacetic acid, EDTA Ethylenedioxy-diethylene-dinitrilo-tetraacetic acid
• Animal food addition to prevent precipitation or absorption of essential metals
• Elution in chelation affinity chromatography (EDTA or EGTA)
• Reduce metal interference when using metal indicators for measuring intracellular cation concentration (Ca2+ in FURA or QUIN).
• Reagent in quantitative complexometric determination of metals
• Removal of complex inhibitory heavy metals from buffer solutions
• Nutrient solution component for microorganisms/plants in hydroculture
Calcium chelators have a high affinity for calcium ions through carboxylic groups. Binding can be affected by pH, other ions, and coordination to other proteins.
Calcium buffers are produced with the help of BAPTA. The chelator can also be used study calcium cell signaling by controlling cytosolic calcium concentration.
General calcium chelator use:
• Controlling Ca2+ levels intracellularly and extracellularly
• NMR analysis of Ca2+
• Research into calcium shuttling, mobilization and spatial calcium buffering