PROTEINS 125 



The micleoproteins may be extracted from tissue, such as the 

 pancreas, by boiling with water. On acidifying with acetic acid 

 the nucleoprotein will precipitate. In this and other properties 

 the nucleoproteins resemble the globulins and the phospho- 

 proteins. From both of these groups they may be distinguished 

 by their content of purine bases. The nucleoproteins contain 

 about the same per cent of phosphorus as the phosphoproteins. 



Lecithoproteins. The lecithoproteins are compounds made up 

 of protein combined with lecithin or some other phosphatid. 

 Little definite information is available concerning these com- 

 pounds. Some investigators put vitellin in this class instead of 

 among the phosphoproteins, for vitellin can only be freed from 

 the lecithin which occurs with it, by extraction with hot alcohol. 

 It has been suggested also that the residue of the blood corpuscles 

 after removing hemoglobin contains a lecithoprotein. Our in- 

 formation about the group is still in a fragmentary and unsatis- 

 factory state. 



Derived Proteins 



The derived proteins are produced when proteins are acted on 

 by various agents. The group is divided into primary and sec- 

 ondary protein derivatives. In making the former the proteins 

 are not greatly changed in their properties. In making the sec- 

 ondary derivatives, extensive alteration or breaking down occurs. 

 The primary derivatives are again divided into proteans, meta- 

 proteins, and coagulated proteins. The secondary derivatives are 

 subdivided into proteoses, peptones, and peptids. 



Primary Protein Derivatives. Proteans. Proteans probably 

 may be formed from most of the simple proteins. Those formed 

 from the globulins have been most studied. If edestin, the glo- 

 bulin from hemp seed, is dissolved in the smallest possible 

 amount of hydrochloric acid, it may be precipitated by adding 

 a small amount of sodium chloride. On adding stronger salt 

 solution a portion of this precipitate will not dissolve. As often 

 as the above process is repeated, a further portion of the protein 

 becomes insoluble. The same results are obtained by the action 



