FAQ: How can I reduce contaminating proteins in a Ni spin column protein purification?

. Add up to 10 mM imidazole to the Lysis Buffer to prevent contaminants from binding (optimal imidazole concentrations must be determined empirically). Employ extra wash steps (e.g., up to 5 washes) with the recommended wash buffer. Increase the imidazole concentration in the wash buffer (test by increasing in 5 mM increments up to 20 mM); higher concentrations of imidazole can result in decreased overall yield of the target protein. The optimal concentration of imidazole will be target/impurity dependent and will therefore require optimization.