INTERACTION OF ORGANIC MOLECULES WITH PROTEINS 



109 



PROTEIN 



CH=CH-C90 



PROTEIN 



Fig. 17 



the specificity may lie. Suppose we compare first, not so much the data of the 

 preceding figure, but, rather, a different question which we were worried about 

 some 6 or 7 years ago. Serum albumin is an outstanding protein in its ability 

 to bind anions in a very general, non-specific way. There are a couple of others, 

 such as beta lactoglobulin, which come somewhere in that neighborhood, but 

 they are not nearly as good, and the great majority of proteins simply will not 

 form complexes non-specifically with the anions which I have shown you. So, 

 let the left side of Fig. 19 represent serum albumin for the moment, and the 

 right side represent, let us say, serum globulin, because that is a good example 

 of a protein which does not bind non-specifically. Gamma globulin will bind the 

 haptens for which it has been built very strongly, but not these other anions. 



What we found was that, if you examine the amino acid composition of these 

 proteins, serum albumin was distinct in that the number of its hydroxyl amino 

 acids was relatively small compared to the number of its carboxylic and cationic 

 amino acids; whereas, in serum globulin, the number of hydroxyl amino acids 

 is relatively large compared to the carboxylic and cationic amino acids. 



Now, if we assume that an OH — O hydrogen bond is stronger than OH — N, 

 then if you have a limited number of hydroxyl amino acids they would tend to 



