Permeation of γ-globulin through microporous membranes in the presence of trace DNA

Permeation of γ-globulin solution through three microfiltration membranes (Planova 35N (mean pore size (r)=0.035 μm), Nucleopore (r=0.1 μm) and Fluoropore (r=0.1 μm)) was investigated. A drastic increase in flux was found with a decrease in DNA in the feed solution, which was normally contained in the protein solution as a contamination in the order of ppb. A DNA–γ-globulin complex having a particle size of 135–225 nm was detected by dynamic light scattering measurements in the γ-globulin solution. The DNA–γ-globulin complex was destroyed by the addition of 0.4 mol/l NaCl in the γ-globulin solution. The flux of the γ-globulin solution through Planova 35N membranes drastically increased with the increase in NaCl concentration in the γ-globulin solution up to 0.1 mol/l. This is explained by a decrease in the DNA–γ-globulin complex in the presence of NaCl in the γ-globulin solution. Only a slight increase in the flux of the γ-globulin solution through Nucleopore membranes was found; on the other hand, a decrease in flux through the Fluoropore membranes was observed when the NaCl concentration in the feed solution of γ-globulin increased. These results suggest that the effect of flux on the concentration of NaCl depends on the pore sizes and structure of the membranes and membrane materials.