The purification of His-tagged proteins is carried out by immobilized metal affinity chromatography (IMAC) with nickel being the preferred metal ion. Elutions of tag proteins is achieved with imidazole.
The resin consists of iminodiacetate coupled to 6% cross-linked agarose beads.
The iminodiacetate binds divalent nickel ion with a capacity of 20-40 moles Ni2+/mL resin.