134 THE PROTEINS AND PROTEASES [ch. 



Legumelin. An albumin found in small (jnantities 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. 132. Extraction of the proteins of the Pea (Pisum sativum) (Osborne and 

 Campbell, 11, 12; Osborne and Harris, 13). As we have seen (Expt. 121), 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 

 saturate the filtrate with solid ammonium sulphate. The globulins, legumin and 

 vicilin, are precipitated out. Filter off the precipitate, and then take up in dilute 

 ammonium sulphate (y^^ saturated) and add saturated ammonium sulphate in the 

 proportion of 150 c.c. to every 100 c.c. of the solution (j% saturation). The legumin 

 is precipitated and can be filtered oft'. Saturate the filtrate with ammonium sulphate : 

 the vicihn is precipitated and can be filtered off. Dissolve up a little of each preci- 

 pitate in 10 "/o sodium chloride, and boil. The vicilin is coagulated, but the legumin is 

 not. Then dissolve up the remainder of the precipitates in dilute ammonium sulphate? 

 and test both the solutions for protein by the usual reactions [Expt. 121, (a)-(rf)]. 



The albumin, legumelin, which occurs only in small quantities in the seeds, can 

 be obtained by dialyzing a water extract of the ground peas until all the globulin is 

 precipitated. On filtering and heating the filtrate, a coagulum of legumelin is formed. 



Proteins of fat-containing Seeds. 



Of the seeds which contain fat as a reserve material, those investi- 

 gated have been found, in contrast to the cereals, to contain largely 

 globulin as reserve protein. In many cases these globulins have been 

 obtained in crystalline form after extraction from the plant. 



The Hemp-seed {Cannabis sativa) contains one of the best-known 

 crystalline globulins, namely edestin. Pure neutral edestin is insoluble 

 in water but soluble in salt solutions. In the presence of acid, however, 

 edestin forms salts which are insoluble in salt solutions. Hence a 

 solution of edestin in sodium chloride is precipitated by even small 

 quantities of acids, and, conversely, a solution of edestin in acid is 

 precipitated by small quantities of salt (Osborne, 8). 



Expt. 133. Extraction and crystallization of edestin from Hemp-seed. Take50gras. 

 of hemp-seed and grind in a coffee-mill. Put the ground seed in a large evaporating 

 dish and add 200 c.c. of 5 "/,, sodium chloride solution. Heat with a small flame and 

 stir constantly. A thermometer should be kept in the dish, and the liquid must not 

 rise above 60" C. Filter off, in small quantities at a time, keeping the solution in the 

 dish warm. On cooling, the edestin separates out from the filtrate more or less in 



