Purification of His-tag-NusG Protein by TSKgel BioAssist Co^<2+>-Chelate Chromatography

By TSKgel BioAssist Co^<2+>-Chelate Chromatography using a linear gradient of imidazole, His-tag-NusG protein was purified as a monomer, dimer, trimer and tetramer eluting on 85, 130, 170 and 200 mM imidazole, respectively. These oligomers were estimated to be under a chemical equilibrium to each other. These results were not obtained by a step-wise elution with a high concentration of imidazole. On the other hand, the linear gradient elution mode was demonstrated to be useful for separation of the monomer and oligomers