The conformation of wheat gluten proteins. The secondary structures and thermal stabilities of α-, β-, γ- and ω-Gliadins

The secondary structures of α-, β-, y- and ω-gliadins were studied by circular dichroism spectroscopy. The ω-gliadins contained no detectable α-helix or β-sheet, but were rich in β-turns. Increasing the temperature of a solution in 70 % (v/v) aqueous ethanol from 20 to 80°C resulted in a conformational change, with an increase in class B β-turns. In contrast, the α-, β- and γ-gliadins contained α-helix (30–35%) and β-sheet (about 10% in α-gliadins). Heating resulted in an increase in aperiodic structure, with partial loss of the α-helical content. These results indicate that whereas the ω-gliadins are stabilised by strong hydrophobic interactions, the main stabilising forces in the α-, β- and γ-gliadins are covalent disulphide bonds and non-covalent hydrogen bonds.