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 K6 Na4 [Ni4 (H2 O)2 (PW9 O34 )2 ] (Ni4 P2 ). The Ni4 P2 is then immobilized onto the surface of SiO2 nanoparticles by self-assembly under electrostatic interactions to give the product of Ni4 P2 @SiO2 composites. Due to the specific affinity between substituted Ni2+ in the polyoxotungsate and the histidine residues of protein, Ni4 P2 @SiO2 composites exhibit highly adsorption selectivity towards histidine protein. This Ni4 P2 @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.