PROTEIN INTERACTIONS WITH AND SEPARATIONS BY SYNTHETIC ULTRAFILTRATION MEMBRANES

Diaflo ultrafiltration (UF) membranes from Amicon Corp., polyacrylonitrile (PAN) membranes, and hydrophilized PAN membranes (designated as PAN-H membranes) were evaluated as to their ability to separate serum albumin (SA) from a gamma globulin (gG) fraction at pH 7.0 and 23{dollar}spcirc{dollar}C. High flux PAN-H and YM100 membranes were observed to recover more than 90% of their initial water fluxes upon rinsing with buffer after processing of protein. The best separation of SA from gG was obtained in a thin-channel crossflow cell; no separation was achieved in a stirred cell. The maximum separation corresponded to a permeate containing 2:1 SA:gG under initial feed conditions of 1:1 weight ratio of SA to gG and 1 mg/ml total protein concentration. The best separation was with PAN-H membranes of initial water flux of 200 {dollar}mu{dollar}m/sec-atm. The extent of separation decreased as the recirculation rate in the thin-channel cell was increased, or as the pressure or the initial protein concentration in the feed was increased. As the starting ratio of SA to gG in the feed was increased, the separation of the two increased.; For mixtures of SA-lysozyme and gG-lysozyme, large separation were obtained in both stirred and thin-channel cells with Diaflo and PAN-H membranes of appropriate porosity. Therefore, an increase in the molecular size differential of the proteins facilitated their separation.; The pore size distributions of both Diaflo and PAN/PAN-H membranes were determined by UF of polydisperse dextran. Aqueous gel permeation chromatography analysis generated a sieving profile from 4,000 to 2,000,000 daltons. A log-normal probability function described only the central portions of the dextran sieving profiles.; A mathematical model, based upon purely geometric considerations was developed to relate the flux and solute rejection of a membrane to the pore size distribution and the total number of pores; it proved useful in the comparison of membranes.; The polymeric dyes blue dextran 2000 and Poly R-478 were observed not to be applicable for the measurement of the molecular weight cutoff and flux of all membranes. These dyes were useful, however, for quality control tests of membrane integrity.