Adsorption of α-, β-, γ- and ω-gliadins onto hydrophobic surfaces

Adsorption onto hydrophobic surfaces of α-, β-, γ-, and ω-gliadins from the wheat variety Chinese Spring was studied by means of in situ ellipsometry. Most measurements were conducted in 0 · 01 M phosphate buffer, pH 6 · 0, with the protein concentrations 1, 5 and 25 μg/mL. The adsorbed amount varied between 1 · 3 and 11 · 4 mg/m², which is high considering the low protein concentrations. The concentration dependence was largest for the α-gliadins and lowest for the ω-gliadins. An intermediate concentration dependence was found for the β-and γ-gliadins, which also behaved similarly in all experiments. It was suggested that α-gliadins aggregated at the surface to a larger extent than the other gliadins when the protein concentration was 25 μg/mL. Further, it seemed as β-and γ-gliadins switched from a side-on orientation (major axis parallel to the surface) to an end-on orientation (major axis perpendicular to the surface) with increasing concentration, contrasting to the ω-gliadins that probably had side-on orientation at all concentrations. Sequential adsorption measurements indicated that α-, β-, and γ-gliadins blocked adsorption of ω-gliadins, but could replace ω-gliadins in a previously formed layer.