Millesime L, Dulieu J, Chaufer B
Lab. Physico-Chimie des Biopolymères, UM 27 CNRS-Univ. Paris Val de Marne, Thiais, France.
Bioseparation. 1996 Jun;6(3):135-45.
The fractionation of two proteins, either positively charged (Lysozyme) or negatively charged (bovine serum albumin, BSA) was investigated by varying the ionic strength with unmodified or positively charged inorganic ultrafiltration membranes. Chemical modification was obtained by coating of polyvinylimidazole which amine groups reacted further with bisepoxiranes in order to have both partly quaternized amine group and pH stable network on membrane surface. The retention of the single protein decreases, with ionic strength when electrostatic interactions between the free protein in the bulk and the adsorbed protein onto the membrane are occurring. An increase of single protein retention with modified membranes appears at high ionic strength due to hydrophobic interactions between proteins and polymer coating. For protein mixtures, at low ionic strength (0.015), observed selectivities are more than 10 whatever the membrane used; both membrane fouling and protein-protein interactions occur in the protein mixture. At intermediate (0.25 M) and high (1 M) ionic strengths, the observed selectivity with modified membranes remains stable (about 6) whereas selectively with unmodified membranes decreases and is close to size selectivity. Hence the fractionation of proteins with modified membranes remains satisfactory in the entire range of ionic strengths due to ionic and salt promoted interactions between protein and membranes.
通过使用未改性或带正电荷的无机超滤膜改变离子强度，研究了两种蛋白质的分级分离，这两种蛋白质分别带正电荷（溶菌酶）或负电荷（牛血清白蛋白，BSA）。通过涂覆聚乙烯咪唑进行化学改性，其胺基与双环氧化合物进一步反应，以便在膜表面同时具有部分季铵化的胺基和pH稳定的网络。当本体中的游离蛋白质与吸附在膜上的蛋白质之间发生静电相互作用时，单一蛋白质的保留率会随着离子强度的增加而降低。由于蛋白质与聚合物涂层之间的疏水相互作用，在高离子强度下，改性膜对单一蛋白质的保留率会增加。对于蛋白质混合物，在低离子强度（0.015）下，无论使用何种膜，观察到的选择性都超过10；蛋白质混合物中会同时发生膜污染和蛋白质-蛋白质相互作用。在中等（0.25M）和高（1M）离子强度下，改性膜观察到的选择性保持稳定（约为6），而未改性膜的选择性则降低并接近尺寸选择性。因此，由于蛋白质与膜之间的离子和盐促进相互作用，在整个离子强度范围内，用改性膜对蛋白质进行分级分离仍然令人满意。
