39 6 



POPULAR SCIENCE MONTHLY 



say is that there appears to be some kind of linkage between certain groups in 

 the proteid molecules which is not uncoupled by the enzymes in the body, and 

 that when it is uncoupled, as in acid hydrolysis, then it is impossible for it to 

 be coupled up again in the body. This combination, which the cells can neither 

 take to pieces nor put together again, must be present, in order that the other 

 component parts of the proteid molecule may gather about them and group 

 themselves round them when the synthesis of proteids is to occur. These con- 

 siderations appear to suggest that the synthetic processes here involved may be 

 the work of the same agent as the hydrolytic, the limitations in its hydrolytic 

 power determining the limitations of its synthetic activity, as in reversible 

 zymolysis. 



Whether this conception of the matter is wholly correct we can not 

 say, but at all events it is a suggestion as plausible as any that can be 

 offered at the present time. 



Just here we may advantageously consider the nature and propor- 

 tion of the chemical components present in the protein molecule so far 

 as has been ascertained by hydrolysis with acids. Kecently, much work 

 has been done on this subject, especially by Dr. Thomas B. Osborne at 

 New Haven. The accompanying table gives the results with eight 

 typical proteins from the animal and vegetable kingdoms, which may 

 be taken as representative of the present state of knowledge. 



Percentage Yield of Cleavage Products 



Glycocoll 



Alanine 



Valine 



Leucine 



Proline 



Phenylalanine . , 

 Aspartic acid.... 

 Glutaminic acid 



Serine 



Tyrosine 



Arginine 



Histidine 



Lysine 



Ammonia 



Tryptophane .... 

 Cystine 



m c3 

 O V 



0.94 

 4.45 

 0.18 

 11.34 

 3.18 

 3.83 

 3.35 

 6.73 



3.34 

 5.94 

 2.83 

 2.75 

 1.41 

 + 



All the above data from vegetable proteins were furnished by Dr. Thomas 

 B. Osborne and represent his own work and that of his co-workers. 



Perhaps the most impressive fact, certainly the one most quickly 

 discernible, is that a large fraction of the protein molecule, 28-50 



' Emil Fischer, P. A. Levene and R. H. Aders. 

 8 Abderhalden. Cow's milk. 



