114 



THE PROTEINS 



WHEAT 



and also to the fact that its solutions are precipitated by saturating them with 

 sodium chloride or with magnesium sulphate. That it is soluble in pure 

 water and not held in solution by small quantities of salts is shown by the 

 fact that a solution containing a considerable quantity of leucosin when sub- 

 jected to prolonged dialysis and then evaporated to dryness, and the leucosin 

 burned off at a low temperature left a residue of mineral matters weighing 

 less than a milligram. Leucosin is much more readily precipitated by am- 

 monium sulphate than are the albumins of animal origin, for by adding an 

 equal volume of a saturated solution of this salt to solutions containing leu- 

 cosin the latter is almost completely precipitated. 



Iveucosin resembles the animal proteins in ultimate composition, in the 

 proportion of its products of hydrolytic decomposition, and in its physical 

 properties more closely than it resembles most of the seed proteins yet studied. 

 It seems not improbable that this is because it is a constituent of the tissues 

 of the embryo, for its physiological functions are unquestionably different 

 from those of the stored-up food proteins of the endosperm. 



Proteins having the same ultimate composition and, so far as known, the 

 same properties as leucosin are found in the seeds of other cereals. Whether 

 these are identical or not can not be determined by any means now available. 



The ultimate composition of leucosin is shown by the following figures, 

 which are the average of accordant analyses of several preparations : 



Composition of leucosin. 



P.ct. 



Carbon 53.02 



Hydrogen 6.84 



Nitrogen 16.80 



Sulphur 1.28 



Oxygen 22.06 



IOO.OO 



L,eucosin yields the following amounts of the several products of hydrolysis 

 when boiled with strong hydrochloric acid : 



Products of hydrolysis of leucosin. 



P.ct. 



Glycocoll 0.94 



Alanine 4.45 



Amino-valerianic acid o. 18 



Leucine n .34 



a-proline 3 . 18 



Phenylalanine 3-83 



Aspartic acid 3-35 



Glutaminic acid 6 . 73 



P.ct. 



Tyrosine 3 34 



Lysine 2 . 75 



Histidine 2 . 83 



Arginine I 5 .94 



Ammonia 1.41 



Tryptophane present 



50.32 



I,eucosin probably contains a relatively large proportion of tryptophane, 

 for in a series of comparative tests made with a large number of different 



