6 THE AMINO ACIDS 



baking qualities of a flour are influenced by the pro- 

 portions of glutenin and gliadin. 



Albuminoids may be defined as simple proteins 

 which possess essentially the same chemical compo- 

 sition as the other proteins, but are characterized by 

 great insolubility in all neutral solvents. Examples 

 of this group may be found as the organic basis of 

 bone (ossein), of tendon (collagen and its hydration 

 product, gelatin), of ligament (elastin) and of nails, 

 hairs, horns, hoofs, and feathers (keratins). 



Histones are basic proteins which may be looked 

 upon as standing between protamines and the more 

 complex proteins. They are precipitated by other 

 proteins and yield a coagulum on heating which is 

 readily soluble in very dilute acids. The histones are 

 soluble in water but insoluble in ammonia. They have 

 been isolated from varied sources, as globin from 

 hemoglobin, scombron from spermatozoa of the mack- 

 erel, gaduhiston from the codfish and arbacin from 

 the sea-urchin. 



Protqnines are the simplest natural proteins. They 

 are soluble in water, are not coagulable by heat, have 

 the property of precipitating other proteins from their 

 solutions, are strongly basic and form stable salts with 

 strong mineral acids. Examples of protamines are 

 salmin (from the spermatozoa of the salmon), sturin 

 (from the sturgeon), clupein (from the herring), and 

 scombin (from the mackerel). 



