Adsorption on montmorillonite prevents oligomerization of Bt Cry1Aa toxin.

The adsorption of the insecticidal Cry1Aa protein from Bacillus thuringiensis (Bt-toxin) on a model clay surface was studied to understand the structural changes of the protein induced by the clay surface. We studied the adsorption of the monomeric and soluble oligomeric forms of the Cry1Aa toxin as a function of pH and ionic strength conditions on montmorillonite, which is an electronegative phyllosilicate. Cry1Aa secondary structure was determined from the amide I' FTIR absorption profiles.

Fate of prions in soil: trapped conformation of full-length ovine prion protein induced by adsorption on clays.

Studying the mechanism of retention of ovine prion protein in soils will tackle the environmental aspect of potential dissemination of scrapie infectious agent. We consider the surface-induced conformational changes that the recombinant ovine prion protein (ovPrP) may undergo under different pH conditions when interacting with soil minerals of highly adsorptive capacities such as montmorillonite. The conformational states of the full-length ovine prion protein adsorbed on the electronegative clay surface are compared to its solvated state in deuterated buffer in the pD range 3.

Structural effects of drying and rehydration for enzymes in soils: a kinetics-FTIR analysis of alpha-chymotrypsin adsorbed on montmorillonite.

The effects of desiccation and rehydration cycles encountered by extracellular enzymes in soils are studied on -chymotrypsin adsorbed on montmorillonite. The controlled hygrometric FTIR cell used in this study enables to monitor drying and rehydration steps undergone by the -chymotrypsin-montmorillonite suspension or by the enzyme alone. Relative humidity (RH) determines the amount of deuterated water in the FTIR cell atmosphere.

Conformational changes of enzymes adsorbed at liquid-solid interface: relevance to enzymatic activity.

FTIR with attenuated total reflectance spectroscopy was used to study in situ adsorption of enzymes at water-solid interfaces to better understand how conformational changes may monitor enzymatic activity. Because the adsorption process depends on hydrophobic and electrostatic interactions, conformational changes were studied as a function of the nature of the adsorbing substrates, which are hydrophobic or hydrophilic in character. The adsorption kinetics of two examples of serine enzymes, alpha-chymotrypsin (alpha-chym) and Humicola lanuginosa lipase (HLL), were studied.

Conformational changes and orientation of Humicola lanuginosa lipase on a solid hydrophobic surface: an in situ interface Fourier transform infrared-attenuated total reflection study.

This study was done to better understand how lipases are activated at an interface. We investigated the conformational and solvation changes occurring during the adsorption of Humicola lanuginosa lipase (HLL) onto a hydrophobic surface using Fourier transform infrared-attenuated total reflection spectroscopy. The hydrophobic surfaces were obtained by coating silicon attenuated total reflection crystal with octadecyltrichlorosilane.