Molecular flexibility in wheat gluten proteins submitted to heating.
Prolamin proteins are responsible for the network that gives wheat dough its viscoelastic properties. Non-prolamin depleted gluten was prepared under conditions that preserve its functionality. Electron Spin Resonance (ESR) was used to provide information about the dynamics of the protein at temperatures between 5 and 90 degrees C by specific spin labelling of its cysteine residues. The spectra were of a composite type, resulting from at least two populations of spin labels largely differing in molecular mobility. The correlation time of the less mobile nitroxide radicals was determined by saturation transfer ESR. Upon heating there was a transfer from the slow to the fast moving population of radicals, and an increase of mobility of this last catagory that followed the Arrhenius law. The effect of temperature on molecular flexibility was reversible. This was not the case for purified, polymerised glutenin subunits extracted from gluten. Urea created similar modifications on gluten as heat.