A combination of c.d. spectroscopy and computer prediction is used to show that C hordein has an unusual secondary structure with an absence of alpha-helix and beta-sheet, but the presence of regularly repeated beta-turns. This is associated with a repetitive primary structure based mainly on blocks of eight residues. Similar spectral changes occurred when the protein was heated from 6 to 86 degrees C in aq. 70% (v/v) ethanol or dissolved in increasing concentrations (50-100%, v/v) of trifluoroethanol in water. The studies indicated that the conformation is stabilized by strong hydrophobic interactions and by extensive hydrogen-bonding.