144 Perspectives in Microbiology 



theria toxin. Both theories represent triumphs of the bril- 

 liant imaginations of their authors and are compatible with 

 large bodies of existing data. Decisive experiments in favor 

 of one mechanism or the other, or even an alternative proc- 

 ess, are, however, yet to be devised and are urgently 

 needed. 



Antibodies may also be considered for a moment as an 

 introduction to the topic of chemical constitution and im- 

 munological specificity. Since all efforts have failed to 

 demonstrate differences between normal globulins and 

 antibodies in physical, chemical, or immunological prop- 

 erties other than the capacity to combine with an antigen, 

 Pauling's hypothesis of a difference in folding of the 

 polypeptide chains has gained acceptance by default. New 

 techniques and new experiments are needed in this diffi- 

 cult area. 



Specif! CI fies of Protein Antigens 



Nor is the question of the specificities of protein anti- 

 gens in a more satisfactory state. The new methods for the 

 determination of terminal amino acids and their immedi- 

 ate neighbors in the peptide chains of proteins, though 

 laborious, offer hope that the fine structures of the smaller 

 proteins, at least, will eventually be worked out. Until this 

 is done, scarcely anything definitive can be said to relate 

 chemical structure to the specificity of proteins. True, the 

 wide difference in specificities between native and dena- 

 tured egg albumin, for example, tells us that in the native 

 protein outcroppings of adjacent peptide chains, or clus- 

 ters of amino acids, probably constitute specific groupings 

 that are altered when their arrangement is dispersed by 

 the unfolding characteristic of denaturation. Paul Maurer 

 has also shown that in the same protein, crystalline chicken 

 egg albumin, about one quarter of the free amino groups 

 may be removed without measurable change in immuno- 



