Self-organization of gliadin in aqueous media under physiologicaldigestive pHs

HERRERA GEORGINA; VEUTHEY TANIA V; DODERO VERONICA I

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016 vol. 141 p. 565 - 575

0927-7765

Here we showed that gliadin, a complex protein system related to celiac disease and other human dis-eases, is spontaneously self-organized in a very dilute solution at pH 3.0 and 7.0 in water under low ionicstrength (10 mM NaCl). The spontaneous self-organization at pH 3.0 increases the apparent solubilitydue to the formation of finite sized aggregates, such as those formed in the micellization of amphiphilicmolecules. Switching the pH from 3.0 to 7.0 lead to a phase separation, however part of the nano-particlesare stable remaining disperse in water after centrifugation. Also, beside the pH change led to changesin protein composition and concentration, we determined that the secondary structure of both systemis the same. Moreover, Tyrs are slightly more buried and Trps are slightly more exposed to water at pH7.0 than those at pH 3.0. Electron microscopy techniques showed that both gliadin systems are com-posed of nanostructures and in the case of pH 7.0 amorphous microaggregates were found, too. Onlynanostructures at pH 3.0 showed a micromolar binding affinity to Nile red probe, suggesting the pres-ence of accessible hydrophobic patches which are not more accessible at pH 7.0. All our results suggestthat gliadin is able to self-organized at pH 3.0 forming protein micelles type nanostructures ( = + 13,42 ± 1.55 mV), meanwhile at 7.0 the decrease of superficial charge to of +4, 78 ± 0.48 mV led to theformation of stable colloidal nanoparticles, unable to interact with Nile red probe. Our findings may opennew perspectives for the understanding of gliadin ability to avoid proteolysis, to reach and cross theintestinal lumen and to trigger different immunological disorders.