INTERACTION OF ORGANIC MOLECULES WITH PROTEINS 



95 



2 2- 



O 



1- 



2n; pH 5 



Zft; pH 4 



No 2n 



Fig. 3. Mediating effect of Z\\' 

 by pepsin. 



LOG [OYq] UNBOUND 



in the binding of pyridine-2-azo-;'-dimethylaniline 



There could be several reasons why this effect might occur. First, in Fig. 4 

 let me show you the scheme which we are rather certain is true. For the moment 

 ignore the zinc and consider the dye molecule. This specific structure can be 

 bound by the protein, pepsin, or by serum albumin. In the absence of zinc, 

 however, the amount of binding is small and probably due to the hydrogen 

 bond shown (Fig. 4). 



PROTEIN 



• Zn 



s 



(^H^H-(^k(s.\^i) 



Fig. 4 



