FORMATION OF A POLYMER COMPLEX BETWEEN BOVINE SERUM-ALBUMIN AND SODIUM CHONDROITIN-6-SULFATE IN AN AQUEOUS-PHASE AND ON A SOLID WATER INTERFACE OF KAOLIN/

A water-insoluble polyelectrolyte complex (PEC) was formed by mixing b ovine serum albumin (BSA) with sodium chondroitin-6-sulfate (Na(2)Chs) at a pH lower than an isoelectric point (iep) of BSA. A PEC was also formed on the surface of kaolin via concurrent and/or cooperative adso rption of these two polymers on it. As a result, the aggregation of ka olin particles was induced and accelerated by virtue of an interpartic le bridging effect of the PEC formed on the surface. On the other hand , water-soluble PEC was formed in an aqueous phase at a pH higher than the iep of BSA through an electrostatic attractive force between the negative charge of Na(2)Chs and the positive charge of patches on BSA. However, a strong effect on the aggregation of kaolin particles was n ot observed. The binding ratio of BSA to Na(2)Chs, R, in an aqueous ph ase and on the surface of kaolin was obtained by chemical analysis as a function of the pH of its mother solution. The R-value was affected not only by the pH but also by the initial mixing ratio of BSA to Na(2 )Chs, the concentration and species of an added salt, the net charge o f the polymers, the charge patches on BSA, and so on. The effect of bi nding the phosphate ion to BSA and kaolin on PEC formation was studied in detail. The significance of PEC formation in biological tissue is emphasized.