title: Self-organization of gliadin in aqueous media under physiological digestive pHs.
abstract: Here we showed that gliadin, a complex protein system related to celiac disease and other human diseases, is spontaneously self-organized in a very dilute solution at pH 3.0 and 7.0 in water under low ionic strength (10mM NaCl). The spontaneous self-organization at pH 3.0 increases the apparent solubility due to the formation of finite sized aggregates, such as those formed in the micellization of amphiphilic molecules. Switching the pH from 3.0 to 7.0 lead to a phase separation, however part of the nano-particles are stable remaining disperse in water after centrifugation. Also, beside the pH change led to changes in protein composition and concentration, we determined that the secondary structure of both system is the same. Moreover, Tyrs are slightly more buried and Trps are slightly more exposed to water at pH 7.0 than those at pH 3.0. Electron microscopy techniques showed that both gliadin systems are composed of nanostructures and in the case of pH 7.0 amorphous microaggregates were found, too. Only nanostructures at pH 3.0 showed a micromolar binding affinity to Nile red probe, suggesting the presence of accessible hydrophobic patches which are not more accessible at pH 7.0. All our results suggest that gliadin is able to self-organized at pH 3.0 forming protein micelles type nanostructures (ζ=+13, 42 ± 1.55 mV), meanwhile at 7.0 the decrease of superficial charge to ζ of +4, 78 ± 0.48 mV led to the formation of stable colloidal nanoparticles, unable to interact with Nile red probe. Our findings may open new perspectives for the understanding of gliadin ability to avoid proteolysis, to reach and cross the intestinal lumen and to trigger different immunological disorders.
authors.affiliation: Departamento de Química-INQUISUR, Universidad Nacional del Su- CONICET, Av. Alem 1253, Bahía Blanca, Argentina.
authors.forename: María G
authors.initials: MG
authors.lastname: Herrera
authors.affiliation: Departamento de Química-INQUISUR, Universidad Nacional del Su- CONICET, Av. Alem 1253, Bahía Blanca, Argentina.
authors.forename: Tania V
authors.initials: TV
authors.lastname: Veuthey
authors.affiliation: Departamento de Química-INQUISUR, Universidad Nacional del Su- CONICET, Av. Alem 1253, Bahía Blanca, Argentina; Universität Bielefeld, Fakultät für Chemie, Organische Chemie, Universitätsstr. 25, 33615 Bielefeld, Germany. Electronic address: veronica.dodero@uns.edu.ar.
authors.forename: Verónica I
authors.initials: VI
authors.lastname: Dodero
mesh_terms: D002942:Circular Dichroism; D005903:Gliadin / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008823:Micelles; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D053758:Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D009994:Osmolar Concentration; D010940:Plant Proteins / Q000737:chemistry*; D017433:Protein Structure, Secondary; D014908:Triticum / Q000378:metabolism; D014867:Water / Q000737:chemistry*
chemical_list: D008823:Micelles; D010940:Plant Proteins; D014867:Water; D005903:Gliadin
keywords: Biophysics; Colloids; Electron microscopy; Gliadin nanostructures; Gliadin related disorders; Nile red binding