Influence of pH and lipid membrane on the liquid–liquid phase separation of wheat γ-gliadin in aqueous conditions

• Published in: Journal of colloid and interface science Vol. 668; pp. 252 - 263
• Main Authors: Cochereau, Rémy, Voisin, Hugo, Solé-Jamault, Véronique, Novales, Bruno, Davy, Joëlle, Jamme, Frédéric, Renard, Denis, Boire, Adeline
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15-08-2024; Elsevier
• Subjects: Food engineering; Life Sciences
• ISSN: 0021-9797; 1095-7103; 1095-7103
• DOI: 10.1016/j.jcis.2024.04.136

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Protein body (PB) formation in wheat seeds is a critical process influencing seed content and nutritional quality. In this study, we investigate the potential mechanisms governing PB formation through an in vitro approach, focusing on γ-gliadin, a key wheat storage protein. We used a microfluidic technique to encapsulate γ-gliadin within giant unilamellar vesicles (GUVs) and tune the physicochemical conditions in a controlled and rapid way. We examined the influence of pH and protein concentration on LLPS and protein-membrane interactions using various microscopy and spectroscopy techniques. We showed that γ-gliadin encapsulated in GUVs can undergo a pH-triggered liquid–liquid phase separation (LLPS) by two distinct mechanisms depending on the γ-gliadin concentration. At low protein concentrations, γ-gliadins phase separate by a nucleation and growth-like process, while, at higher protein concentration and pH above 6.0, γ-gliadin formed a bi-continuous phase suggesting a spinodal decomposition-like mechanism. Fluorescence and microscopy data suggested that γ-gliadin dense phase exhibited affinity for the GUV membrane, forming a layer at the interface and affecting the reversibility of the phase separation.