330 



FINE-STRUCTURE OF PROTOPLASMIC DERIVATIVES 



III 



pronounced dipole character, there is a strong mutual attraction 

 between amino acids. In +H3N.CH3.C02~ this leads to the formation 

 of molecular layers when glycine crystallizes. For the other amino 

 acids there is a steric hindrance due to the side chains R, which prevent 

 the formation of closelv packed layers. Those amino acids therefore 



-T 





- -I 



X'-- 



Fig. 1 66 



Fig. 167 



I 



Fig. 166. Aggregation of amino acid dipoles by three causes threefold symmetry. Peptide 

 bonds are not yet realized (from Scheibe, 1948). Fig. 167. Plate of 24 amino acid groups 

 of three. Groups I (double rings) lie in a somewhat higher plane than groups II (simple 

 rings) ; opposite borders of the hexagon differ from each other, causing polarity in the 

 direction of the arrows. X' — Z cross-section (from Scheibe, 1948). 



associate in threes with the side chains R, pointing in three different 

 directions in the plane in which -NH3+ and -COO" lie (Fig. 166). 

 These groups of three attract each other, forming hexagonal rings. 

 In such a ring three groups lie in a somewhat higher plane and three 

 in a lower one (Fig. 167). The hexagonal rings represent a molecular 

 layer with trigonal symmetry. These layers can be superimposed, 

 yielding a hexagonal crystal lattice. The peculiarity of such a crystal 

 is that it consists of amino acids which still retain their individuality 

 and are not tied together to form polypeptide chains. It represents 

 a "protein" without peptide bonds. 



Denaturation would then imply the formation of peptide bonds 

 between adjacent amino acids. Arguments in favour of such a view 



