94 



PHYSIOLOGICAL CHEMISTRY 



heat, have the property of precipitating aqueous solutions of other pro- 

 teins, possess strong basic properties and form stable salts with strong 

 mineral acids. They yield comparatively few amino acids, among 

 which the basic ones predominate. They are the simplest natural 

 proteins, e.g., salmine from salmon sperm, sturine from sturgeon sperm, 

 clupeine from herring sperm, scombrine from mackerel sperm. 



H. CONJUGATED PROTEINS 



Substances which contain the protein molecule united to some other 

 molecule or molecules otherwise than as a salt. 



(a) Nucleoproteins. Compounds of one or more protein molecules 

 with nucleic acid, e.g., cytoglobulin from cytoplasm, nucleohistone from 

 nucleus. 



(b) Glycoproteins. Compounds of the protein molecule with a 

 substance or substances containing a carbohydrate group other than a 

 nucleic acid, e.g., mucins and mucoids (osseomucoid from bone, tendomu- 

 coid from tendon, ichthulin from carp eggs, helicoprotein from snail) . 



(c) Phosphoproteins. Compounds of the protein molecule with 

 some, as yet undefined, phosphorus-containing substances other than a 

 nucleic acid or lecithin, 1 e.g., casein from milk, owvitellin from egg 

 yolk. 



(d) Hemoglobins. Compounds of the protein molecule with 

 hematin, or some similar substance, e.g., hemoglobin from red blood 

 cells, hemocyanin from blood of invertebrates. 



(e) Lecithoproteins. Compounds of the protein molecule with 

 lecithins. 



HI. DERIVED PROTEINS 



i. PRIMARY PROTEIN DERIVATIVES 



Derivatives of the protein molecule apparently formed through 

 hydrolytic changes which involve only slight alteration of the protein 

 molecule. 



(a) Proteans. Insoluble products which apparently result from 

 the incipient action of water, very dilute acids or enzymes, e.g., myosan 

 from my o sin, edestan from edestin. 



(b) Metaproteins. Products of the further action of acids and alka- 

 lis whereby the molecule is so far altered as to form products soluble in 



1 The accumulated chemical evidence distinctly points to the propriety of classifying 

 the phosphoproteins as conjugated compounds, i.e., they are possibly esters of some phos- 

 phoric acid or acids and protein. 



