3188 - How many His residues are required for successful purification on Ni-NTA resins?

Two Histidines are theoretically sufficient for binding to Ni-NTA resin. However, with 6 Histidines, a much stronger interaction is achieved. Any proteins interacting by 2x His with Ni-NTA are removed in stringent wash steps. Six consecutive His can ideally interact with three Ni-NTA groups.