10. 



Th3S3 amino acids will readily cond-Dnsc, 

 v/ith the 3liTnination of water, to form eithsr 

 chain structurss known as polypeptides, or ring 

 structures knovn as dik etopiperazines . 

 (Smil Fischer, Unt 3rsuchung 3n liber Aminos^iuren, 

 Polypeptide, und ProteSne, 1899 - 1906; 

 Plimr::er's Chemical Constitution of the Proteins, 

 Monographs on Biochemistry, Longmans, 1912) 



3 NHg-CRK-CO-OH = 



im2-CRH-C0-!'^-CRK-C0-lTK-CRPI- CO-OH + 2 HO; 



2 NHg-CRH-CO-CK = 



CRH CO,,^ 



HN ■ ^^IIH + 2 H9O 



"^•CO • CRH--^'' 



^ 



Since protains constitute the principal 

 structure-lDuilding food for animals, and upon 

 digestion are decomposed into amino acids, in 

 v^hich form th 3y are assimilated by th 3 tissues, 

 it is gensrally thought that the phenomenon of 

 grovjth involv 3S condensation processes of a 

 similar character. 



The frequent occurrence of diketopiper- 

 azine rings among th 3 disintegration products of 

 proteins seems to indicate that this may be the 

 form in which the alpha am.ino acid groups occur 

 in nature, but a fatal objection to this thsory 

 is that diketopiperazines cannot grow by con- 

 densation with additional amino acid molecules. 

 If our purpose is to solve th 3 problem of life, 

 then the biological side of the probl 3m must be 

 given full consideration, and we should have but 

 little patience with any theory which explains 

 only the chemical but not the biological facts. 



