I am trying to purify a protein using HIS-select Ni-affinity column (washing with 50mM Tris pH7.5, 50mM NaCl, 30mM imidazole, 3mM BME, 5%glycerol and elution with the same buffer + 250mM imidazole, 500mM Nacl). The protein (pI= 6.04) becomes cloudy/precipitated within 15minutes of after elution. I add EDTA to the eluted protein immediately in the fraction tubes but the protein still precipitate, can anyone suggest how to avoid precipitation of protein.
Thanks and Regards,
