Metal chelate affinity chromatography applications

Metal chelate affinity chromatography finds most prominent application in the affinity purification of recombinant proteins to which a histidine tag has been attached (described later). As protein binding occurs via the histidine residues, this technique is no more inherently useful for the purification of metalloproteins than for the purification of non-metalloproteins (a common misconception, given its name). 

In 1970s, first application of metal-chelate affinity chromatography which is later named as "immobilized-metal (ion) affinity chromatography (IMAC) was perfomed. Metal-chelate chromatography technique exploits selective interactions and affinity between transition metal immobilized on a solid support (resin) via a metal chelator and amino acid residues which act as electron donors in the protein of interest [25-26]. As well as aromatic and heterocyclic compounds, proteins such as histidine, tyrosine, tyriptophane and phenylalanine posses affinity to transition metals which form complexes with compounds rich in electrons [25,27]. 

Liquid chromatography is rather more widely applicable than gas-liquid chromatography and in some forms has the capability to handle larger amounts of substance. All the main forms of LC are used, namely adsorption, partition, ion exchange, and gel filtration, and some newer forms of chromatography including metal-chelate adsorption, hydrophobic adsorption, and, particularly for biochemicals, affinity chromatography. 

Finally, it should be pointed out that until now the application of ion chromatography to the analysis of heavy and transition metals such as iron, copper, nickel, and manganese in the ppb range in 50% sodium hydroxide solution [96, 97] was not possible. A concentration procedure developed by Kingston et al. [98] is used for the AAS analysis of heavy metals in sea water. It is based on the selective concentration of heavy metals on a macroporous iminodiacetic acid resin, where divalent cations are retained by chelation. Their affinity toward the stationary phase decreases in the order... 

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