Cereal Chem 45:37 - 47. | VIEW
Effect of Disulfide-Bond Cleavage on Wheat Gliadin Fractions Obtained by Gel Filtration.
H. C. Nielsen, A. C. Beckwith, and J. S. Wall. Copyright 1968 by the American Association of Cereal Chemists, Inc.
Cleaving the disulfide bonds of the two fractions obtained from classical wheat gliadin by gel-filtration chromatography provides further evidence that structure and properties of these proteins differ. The higher- molecular-weight (MW) fraction, present in small amount in classical gliadin, has properties of a low-MW glutenin and, therefore, is designated as such in this paper. The viscosity of low-MW glutenin decreases drastically upon disulfide cleavage; also its MW drops from about 125,000 to around 37,000. This decline indicates intermolecular disulfide bonds as in glutenin. Also, the starch-gel electrophoretic pattern of reduced and alkylated low-MW glutenin resembles that of glutenin more than it does that of gliaden. The predominant low-MW fraction (purified gliadin) shows no change in viscosity upon disulfide cleavage; however, it does drop appreciably in weight-average MW (27,000 to 22,000) and its molecular units become more asymmetric as indicated by an increase in frictional ratio. Thus the disulfide bonds of purified gliadin are mostly intramolecular and their cleavage allows the molecules to unfold. The starch-gel electrophoretic patterns of reduced and alkylated classical gliadin and of reduced and alkylated purified gliadin are quite similar.