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Extraction of wheat flour with 1.5 % sodium dodecyl sulphate (SDS) solution dissolved 65-67 % of the total flour nitrogen. The SDS-insoluble proteinaceous material was separated into glycoproteins-I, I1 and I11 by ultracentrifugation. Part of the SDSsoluble proteinaceous material was precipitated by addition of ethanol and separated into glycoproteins-IV, glutenins and globulins. The rest of the dissolved proteinaceous material was separated into glycoproteins-V, gliadins, glycoproteins-VI, and albumins by (NH&SO*-precipitation and gel filtration chromatography.

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With the aid of a 1.5% sodium dodecyl sulphate solution (SDS) the proteins of two Dutch wheat flours were separated into an SDS-soluble and an SDS-insoluble fraction. The SDS-soluble fraction was fractionated with the aid of ethanol precipitation and gel filtration chromatography into albumins, globulins, gliadins, glutenins I1 and 111, and glutelins I, IT, I11 and IV. The SDS-insoluble proteinaceous material was separated into glutenins I and glycoproteins. The protein fractions were identified with the aid of SDS-polyacrylamide gel electrophoresis and amino acid analysis. The glutenins I and I1 consist of A, B and C subunits. Their molecular weights ranged from about 600000 to 10 million. The glutenins 111 consist only of B and C subunits and their molecular weights ranged from 300 000 to 600 000. A hypothesis explains how the glutenins I11 are the precursors for glutenins 1 and IT and how they contribute to gluten's structure. The glutelins I consist of a, / 3 and y subunits and their molecular weights ranged from about 6OOOOO to several millions. The glutelins 11 consist also of tc, , B and y subunits with a molecular weight of about 300000 to 600000, while the molecular weights of the glutelins I11 and IV ranged from 10000 to 200000. All glutelins are insoluble in 70% aqueous ethanol and 5~ urea, but soluble in SDS and 0 . 1~ NaOH. Only the glutelins 111 and 1V are soluble in 0 . 1~ HAc. The globulins consist of a heterogeneous fraction of components, their molecular weights arranged from 98000 to 10000. The gliadins form a heterogeneous but homologous group of polypeptides with an average molecular weight of 35 OOO. The albumins consist of components with molecular weights lower than 15 000. A. Graveland et al.Extraction with 1.5% SDS ( 1 20)Centrifuging ot 40 000 g content of 11 % (N x 5.7) and one of the poor breadmaking variety Tundra with a Protein content of 10.5 %. The flours were defatted with petroleum ether b.p. 40-60 by percolation.Glycoprolein (Light brown layer) GluteninI (gel layer) ChemicalsSodium dodecyl sulphate (SDS, specially purified for biochemical work) was purchased from BDH Biochemicals Ltd, England.Sephadex G-100 and Sepharose CL4B were obtained from Pharmacia Ltd, Sweden. Acrylamide, N,N-methylenebisacrylamide were obtained from UCB (Leuven), Belgium.Precipitation by adding ethanol to 7 0 % centrifuging ot 2000 g Extraction and fractionation of wheat flour proteinsThe extraction and fractionation methods were used as previously describedl (see Figure l), but a few modifications were made in the method of fractionation.