04 A. I. RINGER 



GH 3 



CILXIL CHXH 2 



ir on 



\ 



H 



\ 



CO X C II CO X CHo 



I I 



COOH COOTT 



Glycyl-alan in Alanyl-glyein 



That there is a difference between these two compounds we know from 

 the fact that they behave differently in their physical property of rotating 

 the plane of polarized light. Glycyl-alanin rotates the plane of polarized 

 light 50 to the left, whereas alanyl-glycin rotates it 50 to the right 

 (Abderhalden and Fodor, 1012). 



In the union of glycoeoll, alanin and leuciii, we have six different pos- 

 sible combinations, depending upon the position each amino acid occupies 

 in tho molecule with reference to the other amino acids. That there is 

 a difference between these compounds we know from the fact that they all 

 have a different power of rotating the plane of polarized light : Thus : 



I. Glycyl-alanyl-leucin r 1 20 = ~ 90 



II. Glycyl-leucyl-alanin J D = GO 



III. Alanyl-glyeyl-leucm " = 11 



IV. Alanyl-leucyl-glycin " 30 

 V. Leucyl-alanyl-glyciu = 17 



VI. Leucyl-glycyl-alanin " = -f 20 



With the increase in the number of amino acids the number of isomers 

 increases tremendously, as the following table taken from Abderhalden 

 shows : 



Xumber of amino acids Number of possible compounds 



2 2 



3 6 



4 2-i 



5 120 



6 720 



7 5,OJ:0 



8 40,320 



9 362,880 



