INTERACTIONS OF PROTEINS WITH UNIFORM COLLOIDAL HEMATITE AND CHROMIUM HYDROXIDE PARTICLES .1. ADSORPTION

The adsorption of ovalbumin, gamma-globulin, and lysozyme on uniform spherical hematite and chromium hydroxide particles in aqueous media has been studied as a function of the pH at a constant ionic strength. The uptake of ovalbumin and gamma-globulin was greatest at their isoelectric points and differed little at 10(-2) and 10(-3) mol dm-3 NaNO3. The adsorption of lysozyme was strongly influenced by the ionic strength. The deposition of ovalbumin on hematite in the presence of Mg(NO3)2 was significantly greater than that with NaNO3 under otherwise comparable conditions. Dialysis experiments with ovalbumin against magnesium nitrate solutions showed Mg2+ to be specifically bound to the protein. The shapes of isotherms indicated monolayer coverage for ovalbumin and multilayer coating for lysozyme for both adsorbents. The shapes of isotherms of gamma-globulin on hematite point to a rearrangement of the protein on the particle surface, while a monolayer was found on chromium hydroxide-particles.