IX] PROTEINS AND AMINO- ACIDS 147 



Expt. 137. Extraction of the prolamin^ zein, of the Maize grain. Grind up 100 gms. 

 •of maize grains in a coffee-mill, or preferably use maize meal. Add 250 c.c. of hot 

 95 o/o alcohol. Filter, and concentrate the filtrate, which contains the zein, on a 

 water-bath (or, better, distil in vacuo). Pour a few drops of the concentrated extract 

 into (1) absolute alcohol, (2) distilled water. As in the case of gliadin and hordein, 

 a precipitate of zein will be formed. Then pour the whole extract, after evaporating 

 to a small bulk, into excess of distilled water, and add a little sodium chloride. The 

 precipitate of zein will slowly settle, and can be filtered off. Zein is not readily 

 soluble in acids and alkalies. Hence Millon's and the xanthoproteic tests should be 

 made on the solid material. Zein does not contain the tryptophane nucleus. To 

 demonstrate this, the glyoxylic reaction should be made by shaking up some solid 

 jzein in reduced oxalic acid and adding sulphuric acid and mixing. No purple colour 

 is formed. 



Proteins of Leguminous Seeds {Leguminosae). 



In the Leguminosae, which are starchy seeds, the chief reserve 

 proteins, as contrasted with those of cereals, are globulins. The various 

 proteins occurring may be enumerated as: 



Legumin. A globulin which forms the chief protein in the seeds of 

 the Broad Bean (Vicia Faba), the Pea (Pisum sativum), the Lentil 

 {Ervum Lens) and the Vetch (Vicia sativa). Legumin itself is soluble 

 in water, but occurs as salts which are insoluble in water and soluble 

 in saline solutions. Some portion can be extracted from the seed by 

 water only. 



Vicilin. A globulin occuring in smaller quantities than legumin and 

 found only in the Pea, Bean, and Lentil seeds. 



Phaseolin. A globulin forming the bulk of the protein of the Kidney 

 Bean (Phaseolus vulgaris). 



Conglutin. A globulin forming the bulk of the protein in Lupin 

 {Lupinus lute us) seeds. 



Legumelin. An albumin found in small quantities in the Pea, 

 Broad Bean, Vetch and Lentil. 



Phaselin. An albumin found in small quantity in the seeds of the 

 Kidney Bean (Phaseolus vulgaris). 



Small quantities of proteoses are found in most of the above seeds. 



Expt. 138. Extraction of the proieiris of the Pea (Pisum sativum) (Osborne and 

 Campbell, 13, 14 ; Osborne and Harris, 15). As we have seen (Expt. 127), a certain 

 amount of protein, including globulin, goes into solution when ground peas are ex- 

 tracted with water. A more complete method of extraction is as follows. Grind in 

 a coffee-mill 20-30 gms. of peas, add to the ground mass 50-60 c.c. of 10 % sodium 

 chloride solution and allow the mixture to stand for 1-2 hrs. Then filter off and 



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