Adsorption of Bovine Serum Albumin onto Styrene-Acrylamide Copolymer Latex

SHIRAHAMA Hiroyuki, TAMAI Hisashi, SAKAI Ikunori, SUZAWA Toshiro

doi:10.1246/nikkashi.1985.1285

The adsorption behavior of bovine serum albumin (BSA) onto styrene-acrylamide (AAm)copolymer(P(StfAAm)) latex was investigated as a function of pH and ionic streng th by determining the amount of BSA adsorbed. Polystyrene latex was used as a reference sample. First, the surface characteristics of P(St/AAm) and polystyrene latices were s tudied. Conductometric titration, viscosity and ζ-poetntial measurements of latex dispersions showed that the hydrated polyacrylamide (PAAm) layer existed on the surface of P(St/AAm) latex, and the thickness of its layer increased with increasing the amount of AAm used in the copolymerization (Table 2).<BR>The plateau values of the adsorption isotherms (except the case of P(St/AAm20) latex)indicated, that BSA molecules adsorbed onto P(St/AAm) latex, as well as polystyrene l atex, in a side-on mode near the isoelectric point (iep) of this protein (pH about 5). The amount adsorbed showed a maximum near the iep of BSA. The pH at maximum adsorption shifted to a more acidic region with increasing ionic strength. Further, the amount of BSA adsorbed (particularly at ionic strength 0.1) decreased with increasing the amount of AAm used in the copolymerization, i. e., in the order, polystyrene>P(St/AAm₅)>P(St/AAm₁₀)>P(St/AAm₂₀), throughout the entire range of me asured pH (Fig.7). This result may be attributed to the effect of hydrated PAAm layer existed on the surface of P(St/AAm)latex. The most different point in BSA adsorption between P(St/AAm) and polystyrene latices was that the amount adsorbed onto P(St/AAm) latex was hardly discernible in alkaline region of pH.

Adsorption of Bovine Serum Albumin onto Styrene-Acrylamide Copolymer Latex

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