INTERACTION OF ORGANIC MOLECULES WITH PROTEINS 



105 



H C 

 •5 \ 



S'^ 



'-{2^"='"^ 



COO 



H 



I2-13A 



^NHj 



4- 



PROTEIN 



PROTEIN 



N = N 



I2-13A 



\\ // 



-COO 



NH- 



-I- 



PROTEIN 



Fig. 14 



the para sulfonic acid. So, it seems evident that blocking access to the azo is 

 not really important. 



In that case, then, we thought, as is shown in the next illustration (Fig. 

 14), that perhaps — looking at the bottom part first — the interaction involved 

 the dimethylamino group as well as the carboxyl group. We know the carboxyl 

 must still be involved because, if you remove its charge, ability to be bound by 

 protein disappears. Then, if this group is involved, and if we show, as we have 

 from chemical evidence (Klotz, Burkhard, and Urquhart, 1952), that it is likely 



