ESR Studies on Lipid-protein Interaction in Gluten

Abstract

The interaction of protein with lipid in wheat gluten has been studied by electron spin resonance (ESR). The gluten in the flour suspension was spin-labeled with a fatty acid spin label (N-oxyl-4, 4'-dimethyloxazolidine derivative of 5-ketostearic acid) and washed out from the flour. The ESR spectra of the spin label incorporated in gluten exhibited clearly separated parallel and perpendicular hyperfine splittings. The orientation of the gluten lipid and its fluidity showed temperature dependence. Phase transition was observed at 25°C. Compared with gluten, vesicles of the lipids extracted from flour were found to be in a less oriented, highly fluid state, and with much lower activation energy for rotational viscosity, while the reconstituted gluten, which was prepared by mixing purified gluten protein and the extracted lipids, had a lipid environment similar to that of gluten. The results indicate that the lipid was immobilized in the gluten matrix by strong interaction with protein.