PROTEINS OF ACHA (DIGITARIA-EXILIS STAPF) - SOLUBILITY FRACTIONATION,GEL-FILTRATION, AND ELECTROPHORESIS OF PROTEIN-FRACTIONS

Proteins from Digitaria exilis (acha) and durum wheat were characteris ed by gel filtration (GF), sodium dodecyl sulphate polyacrylamide-gel electrophoresis (SDS-PAGE), and acid-PAGE. The proteins of acha show c ompositional and solubility differences from those of durum studied un der the same conditions. From the acid-PAGE results, 1M urea extracted the gliadins of wheat. However, a urea concentration of up to 6M was necessary to solubilise acha proteins corresponding to alpha-gliadins. The proportion of glutelins and residue proteins in acha was higher t han all other Osborne fractions. The amino-acid composition for acha-p rotein fractions showed significantly greater amounts of hydrophobic a nd sulphur amino acids than those in durum. The enhanced solubility of acha proteins in urea or propanol (in the presence of a reducing agen t) suggests that hydrophobic as well as covalent disulphide interactio ns are responsible for the relative insolubility of acha proteins in c onventional solvents. SDS-PAGE analysis of wholemeal acha flour reveal ed that a major component with molecular weight 25.2 kDa, which was ab sent in durum wheat, forms a basic structural component of acha storag e proteins. GF and SDS-PAGE of the four soluble-protein factions for a cha proteins (albumin, globulin, prolamin, and glutelin) showed that s imilar-molecular-weight components (obtained by GF) were relatively he terogeneous by SDS-PAGE.