title: Osmotic compression of anisotropic proteins: interaction properties and associated structures in wheat gliadin dispersions.
abstract: In this Article, we investigated the interaction properties of wheat gliadins, properties that are at the basis of their functionality in wheat grain and in food matrixes. We established the equation of state of our isolate by osmotic compression and characterized the concentration-induced structural transitions, from the secondary structure of proteins to the rheological properties. We evidenced three thermodynamical regimes corresponding to several structuring regimes. First, for Φ < 0.03, gliadins behave as repulsive colloids, with a positive second virial coefficient, arising presumably from their surface charge density and/or their steric repulsion. No intermolecular interaction was detected by FT-IR, suggesting that proteins form a stable dispersion. In the second regime, the system becomes more easily compressible, i.e., less repulsive and/or more attractive. It is associated with the disappearance of β-sheet intramolecular structures of the proteins in favor of random coils/α-helix and intermolecular β-sheet interactions. This coincides with the appearance of elasticity and the increase of the apparent viscosity. Finally, in the last regime, for Φ > 0.16, FT-IR spectra show that proteins are strongly interacting via intermolecular interactions. A correlation peak develops in SAXS, revealing a global order in the dispersion. Interestingly, the osmotic pressure applied to extract the solvent is higher than expected from a hard-sphere-like protein and we highlighted a liquid-like state at very high concentration (>450 g L(-1)) which is in contrast with most proteins that form gel or glass at such concentration. In the discussion, we questioned the existence of supramolecular assemblies and the role of the solvation that would lead to this specific behavior.
authors.affiliation: UMR IATE, Université de Montpellier, Montpellier SupAgro, INRA, CIRAD, 2, Place Viala, 34060 Montpellier Cedex 1, France.
authors.forename: Adeline
authors.initials: A
authors.lastname: Boire
authors.affiliation: UMR IATE, Université de Montpellier, Montpellier SupAgro, INRA, CIRAD, 2, Place Viala, 34060 Montpellier Cedex 1, France.
authors.forename: Paul
authors.initials: P
authors.lastname: Menut
authors.affiliation: UMR IATE, Université de Montpellier, Montpellier SupAgro, INRA, CIRAD, 2, Place Viala, 34060 Montpellier Cedex 1, France.
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Morel
authors.affiliation: UMR IATE, Université de Montpellier, Montpellier SupAgro, INRA, CIRAD, 2, Place Viala, 34060 Montpellier Cedex 1, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Sanchez
mesh_terms: D016880:Anisotropy; D005903:Gliadin / Q000737:chemistry* / Q000378:metabolism*; D009995:Osmosis; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013816:Thermodynamics; D014908:Triticum / Q000737:chemistry*
chemical_list: D005903:Gliadin