Tetra-nickel substituted polyoxotungsate as an efficient sorbent for the isolation of His6-tagged proteins from cell lysate.

By virtue of the flexible structure of polyoxometalates, Ni2+ is encapsulated into trivacant lacunary tungstophosphate ligands by the form of [Ni4] cluster to offer a tetra-nickel substituted polyoxotungsate K6Na4[Ni4(H2O)2(PW9O34)2] (Ni4P2). The Ni4P2 is then immobilized onto the surface of SiO2 nanoparticles by self-assembly under electrostatic interactions to give the product of Ni4P2@SiO2 composites. Due to the specific affinity between substituted Ni2+ in the polyoxotungsate and the histidine residues of protein, Ni4P2@SiO2 composites exhibit highly adsorption selectivity towards histidine protein. This Ni4P2@SiO2 composite is of high stability, and SDS-PAGE assay indicates that it can be used repeatedly as an efficient sorbent for the isolation of His6-tagged proteins from cell lysate with improved performance when compared with commercial NTA-Ni2+ column.