Cereal Chem 40:137 - 144.  |  VIEW ARTICLE

Studies on Wheat Plants Using Carbon-14 Compounds. XVII. The Pattern of Carbon-14 Incorporation into Some Fractions of Wheat Gliadin.

A. J. Finlayson and W. B. McConnell. Copyright 1963 by the American Association of Cereal Chemists, Inc. 

Wheat proteins were labeled with carbon-14 by injection of acetate-l-C[14] into the stems of different groups of wheat plants at each of five stages of maturity. The portion of gliadin soluble in 0.025N ammonium hydroxide was oxidized with performic acid and five major fractions were isolated therefrom by chromatography on DEAE-cellulose. The fractions differed from each other in chemical properties, amino acid competition, and carbon-14 content. Furthermore, the specific activity of glutamic acid isolated from acid hydrolysates of the gliadin fractions was found to depend markedly upon both the fraction from which it was obtained and the time at which tracer was administered. Although the relationships between the specific activity of glutamic acid and the time of tracer injection are complex, two possible explanations for the results are offered. First, the oxidation of intramolecular disulfide linkages facilitates separation of different gliadin proteins, in which the relative efficiencies of carbon-14 incorporation vary during kernel formation and maturation. Second, or probably as well, by rupturing interpeptide cross-links, the oxidation produces polypeptide chains each with its own chemical properties, amino acid composition, and biosynthetic history.