SUMMARY. 



Ill 



proved to contain such a group. Other evidence than that given by the 

 Molisch reaction is required before the presence of a carbohydrate group in 

 this protein can be assumed. 



Nearly two-thirds of the total sulphur in gliadin is split off as sulphide 

 by boiling with alkalis, which would indicate the possibility that all the 

 sulphur is contained in a cystine complex. The amount of cystine isolated 

 is far below that required by such an assumption. The determination, 

 however, of this substance is not quantitative, and the figure given does not 

 necessarily prove that all of the sulphur may not be contained in a cystine- 

 yielding complex. 



The specific rotation of gliadin in 80 per cent by volume ethyl alcohol, ac- 

 cording to determinations by the writer, which agree closely with those of 



20 

 others, is (a) -^- = 92.3. 



The specific rotation in solvents of alcoholic nature has been recently 

 determined by Mathewson, who gives the following data : 



Methyl alcohol, 70 per cent. 95.65 

 Ethyl alcohol, 70 per cent. 91.95 

 Ethyl alcohol, 60 per cent. 96.66 

 Ethyl alcohol, 50 per cent. 98.45 

 Propyl alcohol, 60 per cent. 101.10 



Phenol, 70 per cent 123.15 



Phenol, anhydrous 131.77 



Paracresol 121.00 



Benzyl alcohol 53. 10 



Glacial acetic acid 78.60 



The amount of gliadin in different varieties of wheat differs to a large 

 extent, as shown by a considerable number of determinations that have been 

 recorded. Thus Teller found in a sample of Canadian white winter wheat 

 2.74 per cent, in one of Oregon white winter wheat 2.85 per cent, and 

 in a red spring wheat from South Dakota 8.15 per cent. In other varieties 

 of wheat he and others have found quantities falling between these figures. 



Although the total quantity of gliadin in the sample of red wheat above 

 mentioned was nearly three times as great as in that of the white wheat, its 

 percentage of the total proteins was much more uniform, being 42.5 and 34 

 per cent respectively. This appears to be generally true for most of the 

 wheats that have been examined. 



Thus Shepard has found in 13 samples of durum wheat that the gliadin 

 formed from 40.2 to 48.6 per cent of the total protein (N X 5.7), in 9 sam- 

 ples of Northwestern spring wheat from 44.2 to 49 per cent, in 4 samples 

 of Kansas hard winter wheat from 40 to 50.7 per cent, and in 3 samples of 

 soft winter wheat from 40 to 47.4 per cent. The figures given by others are 

 similar, though a few fall between somewhat wider limits. It would seem 

 safe to say that in the majority of wheats the gliadin forms from 40 to 50 

 per cent of the total proteins, and that its absolute amount depends chiefly 

 on the total protein content of the seed. 



