Electrosurface properties of poly(styrene-co-acrolein) latexes with the protein-modified surface

The effect of pH on the electrophoretic mobility of poly(styrene-co-acrolei n) microspheres is studied. It is established that pH(IEP) is equal to 2.0. The abnormal dependence of the electrophoretic mobility of latex particles on NaCl concentration is obtained. It is shown that the exchange capacitie s of H+ and OH- ions are much lower than the surface concentrations of carb oxyl and aldehyde groups, pH(PZC) being equal to 6.5. The isotherms of bovi ne serum albumin (BSA) adsorption on the microsphere surface exhibit a patt ern typical of chemisorption; the bound BSA is almost completely responsibl e for the electrosurface properties of microspheres. The values of pH(IEP) fall within the range of 4.3-5.6; the passage from the native to denatured forms of BSA and a decrease in the amount of bound protein results in an in crease in the pH(IEP) and the electrophoretic mobility of particles in the alkaline region of pH. The exchange capacity of the BSA-modified microspher e surface with respect to H+ and OH- ions markedly increases, and pH(PZC) i s equal to 7.5. The results obtained are discussed in terms of the formatio n of the layer of polymer chains enriched with hydrophilic units on the lat ex particle surface and the conformational variations of these chains and B SA macromolecules under the action of a dispersion medium.