Affine magnetic sorbents supported on coal ash microspheres for recombinant protein isolation

The results of the development and utilization of an affine magnetic sorbent with Ni²⁺ ions immobilized on coal ash microspheres are reported. The applicability of the material in the isolation of Histag proteins is demonstrated by examples of the recombinant green fluorescent protein from Clytia gregaria and the Ca²⁺ regulated photoprotein obelin from Obelia longissima. The specific sorption capacity of the sorbent was 2–7 mg/cm³ for medium-size proteins (20–30 kDa). The particles are suitable for chromatography with the presence of chaotropic agents and EDTA. They are easy to manipulate as isolation of a target protein takes 30–35 min. On the one hand, the elevated affinity of the sorbent to proteins rich in native histidines may result in a high degree of irreversible sorption; on the other hand, it allows isolation of such proteins without the introduction of artificial polyhistidine fragments.