Insights into gliadin supramolecular organization at digestive pH 3.0.
Herrera, M. G., Vazquez, D. S., Sreij, R., Drechsler, M., Hertle, Y., Hellweg, T. and Dodero, V. I.
Department of Chemistry, Organic Chemistry III, Bielefeld University, Universitatsstrasse 25, 33615 Bielefeld, Germany.
Instituto de Investigaciones Biotecnologicas (IIB)-Instituto Tecnologico de Chascomus (INTECH), Campus Miguelete Universidad de San Martin (UNSAM), Av. 25 de Mayo y Francia, (1650) San Martin, Buenos Aires, Argentina.
Department of Chemistry, Physical and Biophysical Chemistry, Bielefeld University, Universitatsstrasse 25, 33615 Bielefeld, Germany.
Bavarian Polymer Institute, KeyLab Electron and Optical Microscopy, Bayreuth University, Universitasstr. 30, 95447 Bayreuth, Germany.
Department of Chemistry, Organic Chemistry III, Bielefeld University, Universitatsstrasse 25, 33615 Bielefeld, Germany. Electronic address: veronica.dodero@uni-bielefeld.de.
Alpha-gliadin is a highly immunogenic protein from wheat, which is associated with many human diseases, like celiac disease and non-celiac gluten sensitivity. Because of that, gliadin solution is subject to intense biomedical research. However, the physicochemical nature of the employed gliadin solution at physiological pH is not understood. Herein, we present a supramolecular evaluation of the alpha-gliadin protein in water at pH 3.0 by dynamic light scattering (DLS), cryo-transmission electron microscopy (cryo-TEM) and small-angle-.X-ray scattering (SAXS). We report that at 0.5wt% concentration (0.1mg/ml), gliadin is already a colloidal polydisperse system with an average hydrodynamic radius of 30+/-10nm. By cryo-TEM, we detected mainly large clusters. However, it was possible to visualise for the first time prolate oligomers of around 68nm and 103nm, minor and major axis, respectively. SAXS experiments support the existence of prolate/rod-like structures. At 1.5wt% concentration gliadin dimers, small oligomers and large clusters coexist. The radius of gyration (Rg1) of gliadin dimer is 5.72+/-0.23nm with a dimer cross-section (Rc) of 1.63nm, and an average length of around 19nm, this suggests that gliadin dimers are formed longitudinally. Finally, our alpha-gliadin 3D model, obtained by ab initio prediction and analysed by molecular dynamics (MD), predicts that two surfaces prone to aggregation are exposed to the solvent, at the C-terminus. We hypothesise that this region may be involved in the dimerisation process of alpha-gliadin.
Colloids and Surfaces B: Biointerfaces 165: 363-370 (2018)