CHEMICAL COMPOSITION OF PROTEIN MOLECULE 27 



Elastin again seems to be made up of only three or four amino 

 acids ; spongin is rather more complex. 



The keratins are distinguished by containing more cystine than any 

 other protein; in human hair it exists to the extent of about 14 per 

 cent. (Morner). Tyrosine also is present in fair quantities. 



The presence of diamino acids in all proteins led Kossel to suppose 

 that there was a protamine nucleus (i.e., of diamino acids) in all proteins ; 

 the more recent work, especially that by Osborne and Clapp on the 

 gliadins, where the diamino acids are present in such small amounts, 

 though it supports the theory, yet suggests that proteins may exist 

 in which it is not present, more especially if the view of Emil Fischer 

 be taken that all the proteins we know, even the crystalline ones, are 

 still mixtures of several proteins. The isolation of complexes contain- 

 ing only diamino acids from proteins, where they are combined to- 

 gether, will be the only proof of a protamine nucleus in a protein 

 molecule. 



