PHYSICOCHEMICAL PROPERTIES OF PROTEIN-SMECTITE AND PROTEIN-AL(OH)(X)-SMECTITE COMPLEXES

Proteins (catalase, albumin, pepsin and lysozyme with different molecu lar weights and isoelectric points) were differently adsorbed at pH 7. 0 on the clay fraction of three raw Na-saturated smectites (Crook and Uri montmorillonites and one hectorite). The adsorption isotherms of p roteins on clay minerals showed typical Langmuir characteristics. Lyso zyme was adsorbed under the effect of electrostatic interactions betwe en the opposite charges of clay surfaces and protein molecules, wherea s catalase and albumin were adsorbed under the effect of non-electrost atic forces. Pepsin was held in relatively high amounts only on the su rfaces of hectorite. Proteins were intercalated in the interlayers spa ces of smectites, usually undergoing extensive unfolding. Protein-smec tite complexes showed different behaviour to heating treatment. Some c omplexes remained practically unchanged after heating at 200 degrees C . Presence of 'wrecks' of interlayered materials was found after heati ng at 500 degrees C for two hours. The amounts of proteins adsorbed on the external and interlamellar surfaces of clay minerals, partially c oated with OH-Al species, were much lower than those fixed on the clea n clays. Only lysozyme was intercalated in chlorite-like complexes.