MODIFIED AND CONJUGATED ANTIGENS 347 



Tyrosine-Likk Diazoarsanilic Acid Dye. — In the dye compound 

 wliieh they prepared to use as a synthetic hapten for suppression 

 of the specific precipitate, the structure is not quite the same but 

 it worked quilc Avell. They give its structural formula as follows: 



O 



HO— As— / \— N=N— <^ \— OH 



OH 



(Tyrosine-like) phenoldiiizoarsanilic acid. 



Histidindiazoarsanilic Acid Groups in Gelatin Molecule. — 

 In the modified protein antigen the histidindiazoarsanilic acid 

 groups are thought to be as follows : 



\— As— oil 

 / I 



O /\ OH 



HO— As— / \— N=N- 



OH 



Histidine-Like Diazoarsanilic Acid Dye. — The dye hapten 

 which they prepared for use in suppressing the specific precipitate 

 that normally results from the diazotized arsanilic acid protein 

 (containing histidine) and its antiserum was not quite like the 

 above, but it too worked satisfactorily in suppressing the specific 

 reaction. The artificial dye hapten structural formula is given by 

 Hooker and Boyd* as follows : 



O 



V 



HO— As— <^ S— N=rN 



OH 



N N 



(Histidine-like) imidazoldiazoarsanilic acid. 



•Hooker and Boyd: .1. Immunol. 25: 61, 1933. 



