Colloids and Surfaces B: Biointerfaces, 2018, vol 165pp. 363-370
DOI:10.1016/j.colsurfb.2018.02.053
Abstract
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 0.5āÆwt% concentration (0.1āÆmg/ml), gliadin is already a colloidal polydisperse system with an average hydrodynamic radius of 30āÆĀ±āÆ10āÆnm. By cryo-TEM, we detected mainly large clusters. However, it was possible to visualise for the first time prolate oligomers of around 68āÆnm and 103āÆnm, minor and major axis, respectively. SAXS experiments support the existence of prolate/rod-like structures. At 1.5āÆwt% concentration gliadin dimers, small oligomers and large clusters coexist. The radius of gyration (Rg1) of gliadin dimer is 5.72āÆĀ±āÆ0.23āÆnm with a dimer cross-section (Rc) of 1.63āÆnm, and an average length of around 19āÆnm, 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.
