Immobilised metal chelate affinity chromatography (IMAC) has been widely employed as a powerful separation approach in the purification of a broad range of proteins and peptides. It is based on the specific interactions between certain transitional metal ions, mostly Cu2+, Ni2+, Zn2+ and Co2+ to the exposed amino acid surface chains containing histidine (or cysteine and tryptophane). The presence of several adjacent histidines such as (His)6-tag increases the affinity to immobilised metal ions. Increasingly, chelating resins after charged with suitable metal ions are employed for the purification of histidine-tagged recombinant proteins expressed in bacteria, yeast and mammalian cells. There are other applications of chelating resins to purification of certain native non-tagged proteins as well, such as interferons, lectins, antibodies, serum and plasma proteins, peptides and peptide hormones.
Metal ions can be chelated to the carefully designed porous polysaccharide polymer supports via covalently attached iminoacetic acid (IDA) groups.