H R 



A polypeptide spiral in ITaCl solution. 



Th8 nitrogen atoms will appear in two rows 

 on opposite sides of the spiral, and the complex 

 side chains represented by the R's in the above 

 equations, as well as the carbonyl groups, will 

 likewise arrange themselves along other diametrically 

 opposite lines. Chsmical union will probably take 

 place between the successive carbonyl groups in the 

 manner shown, and also betv\reen the successive 

 nitrogen atoms, the fourth and fifth valencies of 

 which are known to have a peculiar tendency to 

 assume opposite charges. The nitrogen atoms at the 

 ends of the spiral will probably unite with the 

 ions of inorganic salts, the presence of which is 

 necessary for the nourishment of all living 

 organisms. It will be found, upon actually con- 

 structing this spiral of atomic models, that there 

 is ample room for the compl 3X side chains R if the 

 fourth val ency of the alpha carbon atom is occupied 

 by hydrogen, but that the presence of more complex 

 groups in this position would make the spiral 

 structure impossible. We find, however, that the 

 decomposition products of natural proteins always 

 have 3. hydrogen atom in this position. 



