PROTEINS ICQ 



the protein tests thus far, whereas the globulin to be studied will be 

 prepared from a vegetable source. There being no essential difference 

 between animal and vegetable proteins, the vegetable globulin we shall 

 study may be taken as a true type of all globulins, both animal and 

 vegetable. 



EXPERIMENTS ON GLOBULIN 



Preparation of the Globulin. Extract 20-30 grams (a handful) of crushed 

 hemp seed with a 5 per cent solution of sodium chloride for one -half hour at 

 6oC. Filter while hot through a paper moistened with 5 per cent sodium chloride 

 solution. Place the filtrate in the water-bath at 6oC. and allow it to stand for 

 24 hours in order that the globulin may crystallize slowly. In case the filtrate is 

 cloudy it should be warmed to 6oC. in order to produce a clear solution. The 

 globulin is soluble in hot 5 per cent sodium chloride solution and is thus extracted 



FIG. 37. EDESTIN. 



from the hemp seed, but upon cooling this solution much of the globulin separates 

 in crystalline form. This particular globulin is called edestin. It crystallizes 

 in several different forms, chiefly octahedra (see Fig. 37, above). (The crystal- 

 line form of excelsin, a protein obtained from the Brazil nut, is shown in Fig. 38, 

 p. no. This vegetable protein crystallizes in the form of hexagonal plates.) 

 Filter off the edestin and make the following tests on the crystalline body and on 

 the filtrate which still contains some of the extracted globulin. 



Tests on Crystallized Edestin. Microscopical examination (see Fig. 37. 



(2) Solubility. Try the solubility in the ordinary solvents (see page 21). 

 Keep these solubilities in mind for comparison with those of edestan, to be made 

 later (see page 115). 



(3) Millon's Reaction. 



(4) Coagulation Test. Place a small amount of the globulin in a test-tube, add 

 a little water and boil. Now add dilute hydrochloric acid and note that the pro- 

 tein no longer dissolves. It has been coagulated. 



