One-step purification and immobilization of his-tagged protein via Ni2+-functionalized Fe3O4@polydopamine magnetic nanoparticles

Ni 2+ -functionalized Fe 3 O 4 @polydopamine magnetic nanoparticles (Ni 2+ -PD-MNPs) were designed and synthesized by in situ coating of magnetic nanoparticles with polydopamine, followed by conjugation of Ni 2+ to the polydopamine film. The Ni 2+ -PD-MNPs were used to purify His-tagged red fluorescent protein (His-RFP) via affinity interaction between Ni 2+ and the His-tag. The results showed that the Ni 2+ -PD-MNPs had extraordinary selectivity for His-RFP purification. In addition, a Histagged transaminase (ω-transaminase BJ110) was selectively immobilized onto the Ni 2+ -PD-MNPs without purification, and the immobilized enzyme showed improved specific activity, as well as enhanced stability and reusability.