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70 THE: PROTEINS OF THE: WHEAT 



evidence which justifies the conclusion that this substance consists of two 

 distinct protein bodies. Fractional precipitations of this alcohol-soluble 

 protein yield practically the same large proportion of glutaminic acid, so 

 that, in view of their very close agreement in composition and properties > 

 both physical and chemical, there is every reason to believe that only one 

 such protein is present. Gliadin yields a remarkable proportion of gluta- 

 minic acid, much in excess of that from any other known protein and 

 greater than that of any single decomposition product yet obtained in a 

 pure state from any other true protein substance, the protamines, of course, 

 excepted. 



HYDROLYSIS OF GLIADIN. 



There being no sufficient evidence that more than one alcohol-soluble 

 protein occurs in the wheat kernel, no attempt has been made, in preparing 

 large quantities of gliadin for the present investigation, to subject the pro- 

 tein matter extracted by alcohol to any fractional precipitation, but it was 

 separated as completely as possible from all other substances soluble in water > 

 alcohol, and ether. 



The gliadin for this investigation was prepared entirely from gluten, as 

 thereby the water-soluble constituents of the seed are more completely re- 

 moved than by any other method of preparation which can be readily used 

 on a large scale. The wheat flour was kneaded into dough in a domestic 

 * ' bread-mixer, ' ' and then under water in a specially constructed kneading- 

 machine. After frequently decanting and renewing the water, a thoroughly 

 coherent gluten was obtained. This was washed practically starch free in 

 a current of water and, while moist, was ground by passing through a 

 special form of "drug-press," which was a ready means of reducing it to 

 comparatively small pieces. The ground gluten was then extracted with 

 alcohol of such strength that, with the combined water of the gluten, a 

 solvent of 60 to 70 per cent by volume resulted. The extracts were filtered 

 perfectly clear through thick felts of filter paper pulp, and the water-clear 

 solution, free from any trace of opalescence or turbidity, was evaporated to 

 a small volume on a water-bath. The thick sirup that resulted was cooled 

 and then poured, with constant and rapid stirring, into a large volume of 

 distilled ice-water containing a very little sodium chloride. The gliadin 

 was thus precipitated as a filament, which, on stirring, united to a coherent 

 plastic mass. This gliadin was next dissolved by stirring with strong alcohol 

 until all had gone into solution, the water combined with the precipitated 

 gliadin being sufficient to dilute the alcohol to the proper degree. The 

 resulting solution was evaporated to a thick sirup, absolute alcohol being 

 added from time to time in order to hold the gliadin in the solution, since 

 this, during the evaporation, became constantly more aqueous. The thick 



