Adsorption of Proteins, Enzymes and Antibiotics by Montmorillonite

Louis A. Pinck
Soil and Water Conservation Research Division, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland

Abstract: Proteins interact with montmorillonite forming mono- and poly-layer complexes. About 20 percent of the protein in a monolayer complex undergoes microbial decomposition and the X-ray pattern remains unchanged, whereas in polylayer complexes the protein undergoes extensive decomposition and the c-spacings of these complexes shrink from approximately 30 Å to 12 Å +. Urease is adsorbed completely by H-montmorillonite and only partially by basic montmorillonite. Initial release of urease from the clay is attributed to urea acting as a cation. Subsequently the ammonia evolved by the hydrolysis of urea becomes the active cation. Antibiotic-montmorillonite complexes are classified into three groups. Group I contains strongly basic antibiotics, II amphoteric, and III acid or neutral. The average adsorption of antibiotic in mg per g of clay for each group is: I, 186; II, 307; and III, 9. X-ray diffraction data for groups I and II showed expansion of the c-spacing of 4.4 and 7.6 Å, respectively. Bioassays showed no activity for I and appreciable activity for II. The complexes are incapable of diffusing through agar, but the antibiotics must be released first by cationic exchange and then diffuse through the agar.

Clays and Clay Minerals; 1960 v. 9; no. 1; p. 520-529; DOI: 10.1346/CCMN.1960.0090138
© 1960, The Clay Minerals Society
Clay Minerals Society (www.clays.org)