Structural studies of adsorbed protein (betalactoglobulin) on natural clay (montmorillonite)

Abstract

Adsorption of betalactoglobulin on montmorillonite leads to structural changes of the protein accompanied by a partial exfoliation of clay.

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“…The slope and intercept of the plot of t/Γt versus t were used to calculate the K2 rate constant. Values of the Γ (interfacial concentration maximum) and K2 (adsorption kinetic constant) are reported inTable I. K2 values indicates affinity of the protein and polyphenol for the inorganic support and in the present case the value of K2=0.16 obtained demonstrates the high affinity of the BSA with the surface of the montmorillonite[20,38].…”

“…The d001 value is about 1.26 nm before adsorption corresponding to the thickness of the layer and the presence of hydrated sodium in the interlayer space. Upon adsorption of the protein, the d001 peak disappears while the other characteristic reflection peaks of montmorillonite remained intact, hence the hypothesis of a possible partial exfoliation or delamination can be considered [20].…”

“…Adsorption of proteins onto clay minerals has been widely reported in the literature [20][21][22]. It may involve several types of physical and chemical interactions such as cation exchange, electrostatic forces or hydrogen bonding, on the interlayer surface of clay minerals, on the edges or both.…”

“…The positive charge of the protein when the pH is below the IP allows the adsorption on the negatively charged surface of montmorillonite due to electrostatic forces. Various possible mechanisms can describe the interaction between proteins and clays: intercalation, exfoliation or both [20]. Extensive penetration of protein chains into the interlayer space of clays can lead to exfoliation or delamination of the silicate layers [23][24][25].…”

“…The spectra of BSA shows a peak at 175.5 ppm while the one of BSA-Mt displays the same peak at 174.8 ppm assigned for backbone carbonyls. Four peaks between 160 and 110 ppm are assigned to aromatic side chain carbons, including in particular the Cξ from Tyr and Arg residues at 155 ppm[20].…”