Conformation of wheat gluten proteins. Comparison between functional and solution states as determined by infrared spectroscopy.

The conformation of wheat gluten proteins in their functional hydrated solid state (doughy state) has been studied for the first time using attenuated total reflection infrared spectroscopy. The amide I band of functional gluten proteins reveals that, in addition to beta-turns and alpha-helices, these proteins contain a significant amount of intra- and intermolecular extended beta-sheet structures. It appears that the solubilization of gluten proteins results in a major decrease of the amount of beta-sheet structures accompanied by an increase of the content of the beta-turn and alpha-helical conformations. In addition, the alpha-helices appears to be more distorted in solution than in the functional state. Furthermore, spectra of omega- and gamma-gliadins, which are two types of prolamins of differing amino acid sequence and conformation, confirm the results obtained on the functional protein system. These results suggest that viscoelastic gluten proteins may interact through aligned beta-sheets corresponding to their repetitive domains.