Chelating Beads 6FF is immobilized metal ion affinity chromatography. Chelating Beads 6FF with a suitable immobilized metal ion can be used to purify 6xHis-tagged proteins expressed in series of expression vectors, such as E.coli, yeast, insect cells and mammalian cells. Chelating Beads 6FF consists of iminodiacetic acid (IDA) coupled to 6% high crossed linked agarose beads.Chelating Beads 6FF can chelated with different transition metal ions such as Cu²⁺, Zn²⁺, Co²⁺, Ni²⁺ and Fe³⁺. When choosing the desired metal ion, consider the structural requirements underlying the basis of metal chelate-protein recognition.Ni²⁺ is usually the first choice metal ion when purifying most histidine-tagged recombinant proteins from cellular contaminants. Some histidine-tagged proteins might therefore be easier to purify with ions other than Ni²⁺, e.g., Zn²⁺ and Co²⁺.In other cases, i.e. for non-tagged proteins, Cu²⁺ and Zn²⁺ metal ions are the most frequently used. Cu²⁺ ions bind strongly to a wide range of proteins and some proteins will only bind to them. Zn²⁺ ions generally give a weaker binding and in some cases this can be exploited to achieve selective elution of a target protein. In some applications, Co²⁺, Fe³⁺ and Ca²⁺ have also been used.