MODIFIED AND CONJUGATED ANTIGENS 341 



HO HO 



I II I II 



3 H— C— C— 0H+ PCl3= 3 H— C— C— CI + PCOH), 



I I 



NH, NH, 



H H O H CH3 H H O HO 



I I II II I I II I II 



H— N— C— C— i CI + H i— N— C— H = H— N— C— C— N— C— C— OH +HC1 



I ■ -^ I III 



H C=0 H H CH3 



Glycyl OH Glyeyl-alanine 



Chloride Alanine 



and in this compound the terminal carboxyl (-COOH) group is 

 the one from the alanine molecule. Now if this process is re- 

 versed, one may produce the alanyl-glycine with the terminal 

 acid group that of the glycine molecule, thus, 



H H O H H O 



3 H— C— C— C— OH + PCI3 = 3 H— C— C— C— CI + PCOH), 



II II 



H NH, H NH, 



HHO HHO HHO HO 



I I II I I II I I II I II 



H— C— C— C— iCl + Hi— N— C— C— OH = H— C— C— C— N— C— C— OH + HCl 



I I ' I I I I I 



H NH, H H NH3 H H 



Alanyl Glycine Alanyl-glycine 



Chloride 



Linkag'e With Salt-Forming- Groups. — While Pick and others 

 regard the linking of the various haptens to the amino acids as 

 replacement of hydrogen either on the ring or on an amino group 

 attached to the ring, Landsteiner considers that linkage with 

 salt-forming groups takes place in the formation of many of 

 these new antigens. In some instances this might he explained 

 as follows : 



Removal of Acid Properties of an Amino Acid. — If one con- 

 siders a simple amino acid like amino acetic acid, the formula for 

 which is 



H O 



H — C— C — OH ^- lonizable or acid hydrogen 



N— H 



I 

 H \ Basic group 



