DAVID PRESSMAN 



ANTI ORTHO- 

 AZOBENZENEARSONATE 



ANTI META- 

 AZOBENZENEARSONATE 



ANTI PARA- 

 AZOBENZENEARSONATE 



10.0- 

 5.0: 



1.0 



0.1 - 



0.05: 



0.01 



m 



m 



o NNOOH 

 . NOg 

 n CI 

 ■ CH3 

 A NH, 



Fig. 3. Effect of position of substituent on Ko value of hapten 



diate combination with the meta, and least combination with the para, indicat- 

 ing steric interference of the substituent in the meia and para positions. 



In the anti-w/e/a-azobenzenearsonate system, we find the greatest combina- 

 tion with haptens with the substituent in the meta position, where there is no 

 steric interference, and less combination when the substituents are in the ortho 

 or para position. Similarly, with the antibodies specific to the ^ara-azoben- 

 zenearsonate system, greatest combination takes place with para substituted 

 compounds. 



In order to determine more precisely how closely antibodies fit around the 

 hapten group, we have carried out studies with the ortho, meta, and para- 

 azobenzoate ions. We prepared the 0-, m-, and ^(^-hydroxybenzeneazo)benzo- 

 ates and all of the monochlor derivatives (except one) of these compounds 

 with the chlorine in the benzoate ring. We then measured the interaction of 

 the chlor-substituted haptens with the antibody against the ortho, meta, and 

 />ara-azobenzoate ions (Pressman, Siegel and Hall, 1954). 



The results are shown in Fig. 4. Here I have indicated the van der Waals 

 outline of the injected hapten by the dotted lines and the van der Waals out- 

 line of the chlor-substituted hapten by the solid lines. 



