Adsorption of alpha-, beta-, gamma- and omega-gliadins onto hydrophobic surfaces
1999
Ornebro, J. | Wahlgren, M. | Eliasson, A.C. | Fido, R.J. | Tatham, A.S.
Adsorption onto hydrophobic surfaces of alpha-, beta, gamma-, and omega-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 micrograms/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 alpha-gliadins and lowest for the omega-gliadins. An intermediate concentration dependence was found for the beta- and gamma-gliadins, which also behaved similarly in all experiments. It was suggested that 2-gliadins aggregated at the surface to a larger extent than the other gliadins when the protein concentration was 25 micrograms/mL. Further, it seemed as beta- and gamma-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 omega-gliadins that probably had side-on orientation at all concentrations. Sequential adsorption measurements indicated that alpha-,beta-, and gamma-gliadins blocked adsorption of omega-gliadins, but could replace omega-gliadins in a previously formed layer.
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