INTERACTION BETWEEN ALPHA-GLIADIN LAYERS

The interaction between layers of alpha-gliadin has been studied by th e surface force technique. The protein was both deposited according to the Langmuir-Blodgett technique and adsorbed onto hydrophilic mica su rfaces. Deposition was performed at surface pressures of 10 and 20 mN/ m, and contact angle measurements of the hydrophobic films indicated a more homogenous layer al the higher surface pressure. Atomic force mi croscopy images showed no significant differences between surfaces dep osited at the two surface pressures. From the surface force measuremen ts, the contact separation indicated a layer thickness of 65 Angstrom. The long range forces between deposited gliadin layers in the presenc e of 1.0 and 0.1 mM sodium chloride were dominated by electrostatic re pulsion, and the absence of long-range steric forces suggested that th e molecules in the protein film adopt a very compact conformation. Som e adhesive force was obtained upon decompression. The interaction betw een alpha-gliadin layers adsorbed from ethanol solution, and measured in the presence of sodium chloride aqueous solution: was dominated by steric forces. From AFM measurements, the adsorbed film was markedly r ougher than the deposited film, but displayed degree of shorter-range order. (C) 1997 Academic Press Limited.