IX] PROTEINS AND AMINO- ACIDS 141 



Crystalline globulins have also been isolated from the following seeds 

 but have as yet no distinctive names: Flax {Liniim usitatissimurn), Squash 

 (Gucurbita maxima), Castor-oil Bean {Ridnus communis), Coconut (Cocos 

 nucifera), Cotton-seed {Gossypium herbaceum), Sunflower {Helianthus 

 annuus), Radish (Raphanus sativus), Peanut (Arachis hypogaea), Rape 

 (Brassica campestris) and Mustard {Brassica alba). 



It will be seen that the majority of reserve proteins of seeds are 

 globulins. It is probable that native and artificial crystalline proteins 

 are identical in many cases. 



Prolamins. These proteins are characterized by the fact that they 

 are insoluble in water and dilute saline solutions, but are soluble in 

 70-90 Yo alcohol. Such proteins are peculiar to plants, and are formed 

 to a considerable extent in the seeds of cereals. The principal ones which 

 have been isolated are : 



Gliadin found in the seeds of Wheat (Triticum vulgare). 



„ „ „ Rye (Secale cereale). 



Hordein „ „ Barley (Hordeum vulgare). 



Zein „ „ Maize {Zea Mays). 



The properties of the gliadins are demonstrated in Expts. 135, 136 

 and 137). 



Glutelins. The proteins of this group are insoluble in water, dilute 

 saline solutions and in alcohol, but they are soluble in dilute alkalies. 

 Glutenin of wheat is the only well-characterized member of this class 

 which has so far been isolated, though other cereals most probably 

 contain similar proteins. A protein of this nature has also been obtained 

 from seeds of Rice {Oryza sativa). The properties of the glutelins are 

 demonstrated in Expts. 135 and 136. 



Conjugated Proteins. 



Nucleoproteins. Though these proteins probably form constituents 

 of all cells, the only members of the class investigated are those of the 

 wheat embryo. This has been possible since nuclei form a large propor- 

 tion of the tissue of the embryo. They may be regarded as protein salts 

 of nucleic acid, i.e. protein nucleates. On hydrolysis with acids or enzymes 

 they split up into various proteins and nucleic acid. The nucleoproteins 

 are also connected with the purines (see p. 179). 



Nucleic acid. Plant nucleic acids have so far only been investigated 

 from two sources, namely from the embryo of Wheat and from the Yeast 

 cell. These two products appear to be identical, and, on analogy with 



