How can I eliminate contaminating protein in my Ni-NTA 6xHis-tag protein purification?
FAQ ID -102

  • Use 10-20 mM imidazole in the lysis and wash buffers (both for native and denaturing conditions). Optimal imidazole concentrations have to be determined empirically.
  • Increase the NaCl concentration (up to 2 M) in the purification buffers to reduce the binding of contaminants as a result of nonspecific ionic interactions.
  • Add ß-mercaptoethanol (up to 20 mM) to the lysis buffer to prevent copurification of host proteins that may have formed disulfide bonds with the protein of interest during cell lysis.
  • Add detergents such as Triton X-100 and Tween 20 (up to 2%), or additives such as glycerol (up to 50%) or ethanol (up to 20%) to reduce nonspecific binding to the matrix due to nonspecific hydrophobic interactions.
  • Reduce the amount of Ni-NTA matrix. Low-affinity binding of background proteins will be reduced by matching the total binding capacity of Ni-NTA matrix with the expected amount of 6xHis-tagged protein.