88 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



NH CO CHR . NH, NH CO CHR . NH, 

 R.CH CO NH CHR R . C = C(OH) NH CHR 



COOH COOH 



Only one of the asymmetric carbon atoms can undergo this change : the 

 carbon atom which remains unaffected is at the end of a chain of amino 

 acids. 



Hydrolysis of a protein after treatment with alkali should yield a 

 mixture of optically inactive and optically active amino acids. By 

 ascertaining which of the amino acids are active the end members of 

 a chain will be ascertained. Dakin's preliminary results l with gelatin 

 show that lysine, glutamic acid and a part of the alanine and proline 

 are obtained in an optically active form ; the leucine, aspartic acid, 

 phenylalanine, histidine and arginine were entirely inactive. 



Lysine and glutamic acid would thus appear to be at the end of a 

 chain of amino acids. 



'Dr. Dakin has kindly pointed out this phenomenon to me and informed me of these 

 results of his experiments, which have since been published. 



