Effect of self-association on the transport of .alpha.-chymotrypsin across microporous membranes

Abstract

The dependence of the rate of α-chymotrypsin transport across microporous, polycarbonate membranes on enzyme concentration was investigated. It was of interest to determine whether self-association, the extent of which is concentration-dependent, would have a significant effect on the mass transfer coefficient. When the enzyme was solubilized in pH 6.2 and I 0.2 buffer, a significant decrease in the mass transfer coefficient accompanied an increase in solute concentration. Furthermore, when the pH and ionic strength of the solvent were altered, it was found that the concentration dependence of the mass transfer coefficient reflected the degree of self-association known to occur in the different solvents. An analysis of the potential effects of osmotic backflow and excluded volume indicates that self-association is responsible for the observed changes in the mass transfer coefficient. From the practical standpoint, these results suggest that self-association could be promoted in order to alter a solute's rejection coefficient, and membrane transport studies could complement the results of moving boundary and light scattering experiments.