Interlamellar Adsorption of Protein Monolayers on Pure Montmorillonoid Clays

Abstract

ORIENTED flakes of the fine fractions (less than 0.5 µ) of montmorillonite and hectorite, when dipped in protein suspensions at pH values far below their iso-electric point, exhibit a behaviour similar in general to that observed by Gieseking and his collaborators¹. The difference in technique, however, shows a striking modification in the resulting protein-clay complexes. After immersion in gelatin-suspensions of pH 2.5 and concentrations stronger than 1 per cent, unidimensional Fourier syntheses of the X-ray diagrams of the oriented flake suggest that: (a) two monolayers, 4.3 A. thick, of the polypeptide chains of the protein are taken up in the interlamellar space, and completely fill it; (b) each monolayer is strongly adsorbed on the clay mineral sheets, and a high degree of order along the c-axis is obtained in the sandwich thus formed. The X-ray diagram is analogous to that of the glycerol – montmorillonite complex. This lends strong support to the idea that surface adsorptive forces play a major part in the formation of these two-layer organic complexes in montmorillonoid clays.