Bérot S, Chaufer B, Basso Y, Legay C, Popineau Y
Institut National de la Recherche Agronomique, Laboratoire de Biochimie et Technologie des Protéines, Nantes, France.
Biotechnol Bioeng. 1999 Mar 20;62(6):649-58.
Ultrafiltration was applied to the fractionation of neutral vs. charged peptides of similar size. The peptides, produced from gliadins, a major fraction of wheat storage proteins, were obtained by limited hydrolysis with alpha-chymotrypsin in water-ethanol 80/20 (v/v). Peptides, according to their elution by RP-HPLC, were quasineutral (repetitive peptides) irrespective of pH, or positively charged (nonrepetitive peptides) at pH below 5. The transmission through the membranes of the nonrepetitive peptides was less (until sevenfold) than that of the repetitive ones, because of the role of electrostatic repulsion involved in the retention of charged solutes. The difference of transmission was more efficient at acidic pH (3) and low ionic strength with inorganic membranes and in a wider range of pH and ionic strength with membranes modified by coating of positively charged polymers (polyvinylimidazole PVI, polyethyleneimine PEI). A continuous diafiltration process using an inorganic membrane of low molecular cut-off permitted the selective enrichment of the retentate in nonrepetitive peptides (up to 80%) and of the permeate in repetitive peptides (up to 80%) from hydrolysate feed containing about 60/40% of repetitive and nonrepetitive peptides, respectively, with a diafiltration volume of 4.
超滤被应用于分离大小相似的中性与带电肽段。这些肽段由醇溶蛋白（小麦储存蛋白的主要成分）产生，通过在80/20（v/v）水 - 乙醇体系中用α - 胰凝乳蛋白酶进行有限水解获得。根据它们在反相高效液相色谱（RP - HPLC）中的洗脱情况，肽段在任何pH值下都是准中性的（重复肽段），或者在pH低于5时带正电荷（非重复肽段）。由于静电排斥在带电溶质保留中所起的作用，非重复肽段通过膜的透过率比重复肽段低（最多低7倍）。在酸性pH值（3）和低离子强度下，使用无机膜时，以及在更宽的pH值和离子强度范围内，使用涂覆有带正电荷聚合物（聚乙烯基咪唑PVI、聚乙烯亚胺PEI）的改性膜时，透过率差异更为明显。使用低分子截留量的无机膜进行连续渗滤过程，能够从分别含有约60/40%重复和非重复肽段的水解产物进料中，选择性地富集截留物中的非重复肽段（高达80%）和渗透物中的重复肽段（高达80%），渗滤体积为4。
