Nau F, Kerhervé F L, Léonil J, Daufin G, Aimar P
I.N.R.A.-Laboratoire de Recherches de Technologie Laitière, Rennes, France.
Bioseparation. 1992;3(4):205-15.
Ultrafiltration of peptide mixtures is studied under various operating conditions (transmembrane pressure, tangential flow-rate) using two ultrafiltration inorganic membranes M5 and M1 with molecular weight cut-offs, MWCO 10 and 70 kD, respectively. It is shown that the separation of peptides is controlled by a dual mechanism: size exclusion and electrostatic repulsion. When the ionic strength is high enough to screen out the electrostatic interactions, experimental data are in good agreement with a sieving model developed to estimate the intrinsic transmission from the molecular weight of a component and from the MWCO of the membranes. Although the transmission so found is altered by concentration polarisation and pore blocking mechanisms, the results explain the apparent low transmission of peptides by ultrafiltration membranes. If the ionic strength of the fluid is low, electrostatic interactions can influence the transport phenomena, provided that the molecules are highly charged (at pHs away from the pI). For attractive interactions, an apparent partition coefficient larger than 1 is observed. Otherwise, the transmission is lower than predicted by the sieving theoretical equation, as if the partition coefficient were smaller than 1.
使用两种截留分子量分别为10 kD和70 kD的无机超滤膜M5和M1，在各种操作条件（跨膜压力、切向流速）下研究了肽混合物的超滤过程。结果表明，肽的分离受双重机制控制：尺寸排阻和静电排斥。当离子强度高到足以屏蔽静电相互作用时，实验数据与为根据组分分子量和膜的截留分子量估算本征透过率而建立的筛分模型吻合良好。尽管如此得到的透过率会因浓差极化和孔堵塞机制而改变，但这些结果解释了超滤膜对肽的明显低透过率。如果流体的离子强度低，只要分子带高电荷（在远离等电点的pH值下），静电相互作用就会影响传输现象。对于吸引性相互作用，观察到表观分配系数大于1。否则，透过率低于筛分理论方程的预测值，就好像分配系数小于1一样。
