Separation of the ammonium sulfate precipitated protein fraction of mouse ascitic fluid, containing the specific immunoglobulin (pI 6.7-6.8; molecular weight 180000), from ammonium sulfate was investigated by means of non-traditional dialysis, based on the difference in diffusion rates of small and large molecules through porous membranes. The experiments were carried out in spiral membrane modules equipped with a Neosepta (AM-2 or ACS-SB) anion exchange membrane and a microfiltration membrane (Synpore or Sartorius). To enhance the driving force for penetration of ammonium sulfate and low-molecular-weight components from solution of ascitic protein fraction into water, a counterpressure was imposed on the side of microfiltration membrane. The flow rate, counterpressure and the pore sizes of microfiltration membranes had a significant effect on the separation process, as expected. The type of the anion exchange membrane had only a small effect. This process makes it possible to desalt the immunoglobulin fraction with high purity and yield in a few hours instead of 5 days.

Institute of Macromolecular Chemistry Academy of Sciences of the Czech Republic