Interpretation of the pH dependence of protein adsorption on clay mineral surfaces and its relevance to the understanding of extracellular enzyme activity in soil

Quiquampoix, Hervé; Staunton, Siobhán; Baron, Marie‐Hélène; Ratcliffe, George

doi:10.1016/0927-7757(93)80419-f

Cited by 103 publications

(61 citation statements)

References 31 publications

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“…Our analysis also demonstrates that over the entire pD range investigated adsorption of ␣-chymotrypsin on montmorillonite is mainly determined by electrostatic interactions (6,13,16,26,27,29). When the protein and the clay are brought into contact, these interactions result in a dynamic structural transition of the protein which can last up to 1 h. In the 4.5-9 pD range, the unfolding resulting from the adsorption involves about 15-20 peptide units in peripheral ␤-sheets.…”

Section: Discussionmentioning

confidence: 88%

Chymotrypsin Adsorption on Montmorillonite: Enzymatic Activity and Kinetic FTIR Structural Analysis

Baron

Revault

Servagent-Noinville

et al. 1999

Journal of Colloid and Interface Science

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110

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Soils have a large solid surface area and high adsorptive capacities. To determine if structural and solvation changes induced by adsorption on clays are related to changes in enzyme activity, alpha-chymotrypsin adsorbed on a phyllosilicate with an electronegative surface (montmorillonite) has been studied by transmission FTIR spectroscopy. A comparison of the pH-dependent structural changes for the solution and adsorbed states probes the electrostatic origin of the adsorption. In the pD range 4.5-10, adsorption only perturbs some peripheral domains of the protein compared to the solution. Secondary structure unfolding affects about 15-20 peptide units. Parts of these domains become hydrated and others entail some self-association. However, the inactivation of the catalytic activity of the adsorbed enzyme in the 5-7 pD range is due less to these structural changes than to steric hindrance when three essential imino/amino functions, located close to the entrance of the catalytic cavity (His-40 and -57 residues and Ala-149 end chain residue), are oriented toward the negatively charged mineral surface. When these functions lose their positive charge, the orientation of the adsorbed enzyme is changed and an activity similar to that in solution at equivalent pH is recovered. This result is of fundamental interest in all fields of research where enzymatic activity is monitored using reversible adsorption procedures. Copyright 1999 Academic Press.

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Section: Discussionmentioning

confidence: 88%

Chymotrypsin Adsorption on Montmorillonite: Enzymatic Activity and Kinetic FTIR Structural Analysis

Baron

Revault

Servagent-Noinville

et al. 1999

Journal of Colloid and Interface Science

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110

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“…of this protein. 53 From the above discussion, it is clear that in the i.e.p. region, the protein may experience significant conformational changes owing to a change to its molecular surface charge.…”

Section: Interactions Forces Between Adsorbed Vn Layers As a Functionmentioning

confidence: 96%

Direct measurement of interactions between adsorbed vitronectin layers: The influence of ionic strength and pH

Zhang

Bremmell

Smart

2005

J Biomedical Materials Res

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Vitronectin (Vn) is an adhesive protein in the plasma serum and plays an important role in cell attachment, spreading, and proliferation. The interactions between protein bovine vitronectin layers adsorbed onto a silica probe and a mica surface have been investigated with the use of atomic force microscopy (AFM). Adsorption of vitronectin was confirmed by XPS surface analysis. The force-separation curves and pull-off forces were measured as a function of ionic strength and solution pH. The pull-off force (adhesion force) decreased as the salt concentration increased, which suggests that some binding domains of this protein may associate with the ionic species and reduce its binding ability. Discrete jumps, or discontinuities, in the separation force curve were observed to extend to a maximum of 300 nm, evidence that the protein molecules bridge between the surfaces. As a function of pH, the adhesion force on separation of the protein-coated surfaces showed a maximum at pH 5 (i.e.p. of vitronectin), decreasing in magnitude at lower and higher pH values. At pH 5, the approaching curves illustrated a jump-in force; whereas for pH values away from 5, the approaching force curves were repulsive. Correlation of the interaction forces with Vn conformational changes in different pH environments, directly visualized with the use of AFM imaging, was developed. In its i.e.p. region, the Vn molecular conformation appeared to be dense and compact. Significantly, at wounds/injured sites the pH is low (approximately 5) which this study discovered to facilitate adsorption and formation of vitronectin aggregates, known to trigger their subsequent biological functions.

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“…This FTIR study gives information complementary to the NMR study performed on the same system (17,50). The NMR approach was devised to measure the area of the interface between a BSA macromolecule and montmorillonite by following the release of a paramagnetic cation from the clay surface on protein adsorption.…”

Section: Unfolding Process For Bsa Adsorbed On Montmorillonitementioning

confidence: 99%

Conformational Changes of Bovine Serum Albumin Induced by Adsorption on Different Clay Surfaces: FTIR Analysis

Servagent-Noinville

Revault

Quiquampoix

et al. 2000

Journal of Colloid and Interface Science

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218

173

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Interactions between proteins and clays perturb biological activity in ecosystems, particularly soil extracellular enzyme activity. The pH dependence of hydrophobic, hydrophilic, and electrostatic interactions on the adsorption of bovine serum albumin (BSA) is studied. BSA secondary structures and hydration are revealed from computation of the Amide I and II FTIR absorption profiles. The influence of ionization of Asp, Glu, and His side chains on the adsorption processes is deduced from correlation between p 2 H dependent carboxylic/carboxylate ratio and Amide band profiles. We quantify p 2 H dependent internal and external structural unfolding for BSA adsorbed on montmorillonite, which is an electronegative phyllosilicate. Adsorption on talc, a hydrophobic surface, is less denaturing. The results emphasize the importance of electrostatic interactions in both adsorption processes. In the first case, charged side chains directly influence BSA adsorption that generate the structural transition. In the second case, the forces that attract hydrophobic side chains toward the protein-clay interface are large enough to distort peripheral amphiphilic helical domains. The resulting local unfolding displaces enough internal ionized side chains to prevent them from establishing salt bridges as for BSA native structure in solution. On montmorillonite, a particular feature is a higher protonation of the Asp and Glu side chains of the adsorbed BSA than in solution, which decreases coulombic repulsion. C 2000 Academic Press

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Interpretation of the pH dependence of protein adsorption on clay mineral surfaces and its relevance to the understanding of extracellular enzyme activity in soil

Cited by 103 publications

References 31 publications

Chymotrypsin Adsorption on Montmorillonite: Enzymatic Activity and Kinetic FTIR Structural Analysis

Chymotrypsin Adsorption on Montmorillonite: Enzymatic Activity and Kinetic FTIR Structural Analysis

Direct measurement of interactions between adsorbed vitronectin layers: The influence of ionic strength and pH

Conformational Changes of Bovine Serum Albumin Induced by Adsorption on Different Clay Surfaces: FTIR Analysis

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