Storage of Biological Samples for Affinity Chromatography

Appendix 8, extracted from Affinity Chromatography Vol. 3: Specific Groups of Biomolecules, GE Healthcare, 2014

The advice given here is of a general nature and cannot be applied to every biological sample. Always consider the properties of the specific sample and its intended use before following any of these recommendations.

General recommendations

  • Add stabilizing agents, when necessary. Stabilizing agents are often required for storage of purified proteins.
  • Serum, culture supernatants, and ascitic fluid should be kept frozen at -20°C or -70°C, in small aliquots.
  • Avoid repeated freeze/thawing or freeze drying/redissolving that can reduce biological activity.
  • Avoid conditions close to stability limits for example pH or salt concentrations, reducing or chelating agents.
  • Keep refrigerated at 4°C in a closed vessel to minimize bacterial growth and protease activity. Above 24 h at 4°C, add a preserving agent if possible (e.g., merthiolate 0.01%).

Sodium azide can interfere with many coupling methods and some biological assays and can be a health hazard. It can be removed by using a desalting column (see Appendix 1, Sample preparation).

Specific recommendations for purified proteins

  • Store as a precipitate in high concentration of ammonium sulfate, for example 4.0 M.
  • Freeze in 50% glycerol, especially suitable for enzymes.
  • Avoid the use of preserving agents if the product is to be used for a biological assay.

Preserving agents should not be added if in vivo experiments are to be performed.

Store samples in small aliquots and keep frozen.

  • Sterile filter to prolong storage time.
  • Add stabilizing agents such as glycerol (5% to 20%) or serum albumin (10 mg/ml) to help maintain biological activity. Remember that any additive will reduce the purity of the protein and might need to be removed at a later stage.
  • Avoid repeated freeze/thawing or freeze drying/redissolving that can reduce biological activity.

Certain proteins, including some mouse antibodies of the IgG3 subclass, should not be stored at 4°C as they precipitate at this temperature. Keep at room temperature in the presence of a preserving agent.