474 



PROTOPLASM 



odadecapeptide the molecule of which contains 15 glycyl 

 (— NH-CHa-CO— ) and 3 leucyl (— NH-CH(C4H9)-CO— ) groups. 

 The molecular weight of this substance is 1,213, and its prop- 

 erties are much like those of the natural proteins. 



Egg Albumin 



Protein Structure. — The fact that the proteins can be broken 

 down into their component parts and the even greater achieve- 

 ment of building them up by combining these parts have led to 

 some knowledge of their structure. Where this knowledge is 

 lacking, and in all cases as a matter of convenience, that part 

 of the protein molecule about which we know little is indicated 

 by the letter R; attached to it are the two known radicals NH2 

 and COOH, which form a part — and so important a part — of 

 every protein molecule. The structural formula becomes simply 



R 



.NH, 



^COOH 



However, much more than this has been attempted in the way 

 of an interpretation of protein structure. The protein molecule 

 and its derivatives are generally recognized as possessing the 



