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The interactions occurring in the protein complex of wheat dough have been characterized by the extraction and molecular sieving techniques supported with optical methods as well as with some rheological examinations. The effects of wheat albumin, soya globulin and beta-lactoglobulin preparations have been determined. The interactions of dough protein complex with soluble pentosans isolated from rye flour and with lipid fractions of wheat embryo were analysed as well. In most cases the advanced aggregation, leading to formation of high molecular weight product similar to glutenin fraction and the increase of insoluble protein fraction were observed. The albumin, globulin and gluten type proteins participated in the interactions. The beta-lactoglobulin generally caused an intense disaggregation of the dough protein complex. The increase of low molecular weight fraction contents was, however, accompanied with formation of some quantities of the high molecular weight complex.

Proteins extracted from wheat flour with 0.01 M-sodium pyrophosphate buffer, pH 7.0, and with 0.05 M-acetic acid were centrifuged, dialysed against 0.005 hr-sodium acetate buffer pH 4.1, concentrated by ultrafiltration at 4', and lyophylised. The proteins were dispersed in 0.005 M-sodium acetate buffer pH 4.1 and fractionated on Sephadex G-IOO and Sephadex G-zoo columns. Based on separation according to average mol. wt. on Sephadex G-100, the pyrophosphate-dispersible proteins contained eight, and the following acetic acid-dispersible proteins six fractions. Proteins extracted directly with 0.05 M-acetic acid were separated into seven fractions. The distribution of protein moieties of different average molecular-size ranges is detailed and shown to be different in the different extracts. Aggregation and disaggregation phenomena were observed during repeated re-chromatography of high-and intermediate-molecular weight proteins. Ultra-centrifugation in a stepwise sucrose gradient at 45,000 g. at 4' and fractionation by polyacrylamide-gel electrophoresis separated the protein into slow-moving, intermediate-and high-molecular weight moieties. The relative distribution of these moieties was correlated with the mol. wt. of the fractions eluted from Sephadex columns.

Proteins were extracted from wheat flour with seven different extractants. Extraction with 3.0 M-urea at pH 7.0 and a t 4O solubilised practically all the proteinaceous material in wheat flour. Extracted proteins were dialysed against 0.005 M-acetate buffer pH 4.1. concentrated by ultrafiltration and lyophylised. Proteins were fractionated in acetate buffer pH 4.1 by sucrose gradient ultracentrifugation or on Sephadex G-100, and the viscosity of Sephadex G-roo eluates was determined. Adding N-ethylmaleimide alone, but not in the presence of urea, reduced the yields of proteins extracted in a two-step procedure and increased tke relative amounts of proteins of high molecular weight. Adding urea resulted in distinct separation of intermediate-sized proteins into two fractions. Proteins were fractionated on Sephadex G-IOO into up to eight fractions, varying in molecular weight, and they were rechromatographed on Sephadex G-IOO or G-200. The results indicated aggregation and disaggregation phenomena, and heterogeneity of protein fractions under conditions used. JANKIEWICZ c POMERANZ-WHEAT FLOUR PROTEINS. rr 653 IntroductionImportant questions in the chemistry of wheat proteins in general, and of high molecular weight wheat gluten in particular, concern the type of bonds that hold polypeptide strands together and the nature of intermolecular crosslinks responsible for gluten structure. Considerable progress is being made in discovering and elucidating the nature of probable crosslinks in a variety of biological systems. This has resulted in an impressive accumulation of information and contributes to our understanding of physical properties of biological systems, and effects of hydration, mechanical treatment and oxidising agents on the systems.It is apparent that only a start has been made in understanding the role of various crosslinks in wheat proteins, and in correlating rheological properties of wheat dough with the structure of gluten proteins. The role of sulphydryl and disulphide groups in forming gluten structure and the hypothesis of the reacting systems have been described.lI2 The reactivity of sulphurcontaining groups of wheat proteins explains, however, only some features of dough rheology. Nearly one-fourth of wheat nitrogen is amide nitrogen, glutamine accounting for most of the amide content.3 Esterification of side-chain amide groups of gluten and its fractions affects solubility, viscosity and c~h e s i o n .~ We have recently compared effects of N-ethylmaleimide and urea on rheological properties of wheat dough, and have found that, in the presence of 3 M-urea, dough structure was completely and almost instantaneously destroyed.s Methods to isolate and fractionate wheat flour proteins are described in another paper.6 This present study was to evaluate the effects of urea and N-ethylmaleimide on the isolation and on characteristics of wheat flour proteins, as well as to correlate these effects with gluten properties.