3z8 



FINE-STRUCTURE OF PROTOPLASMIC DERIVATIVES 



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elementary regions of which harbour globular macromolecules of 

 about 40,000 molecular weight, a figure that tallies with the values 

 found in the ultracentrifuge. 



Fig. 164 shows the result of such an investigation of crystallized 

 insuUn by Crowfoot (1938, 1941). It is characterized by contour lines 



Fig. 164. Patterson-Fourier diagram of crystallized insulin (from Crowfoot, 1938). 



in the unit cell of the lattice which are derived from intensity measure- 

 ments of the X-ray diffraction pattern. The resulting so-called 

 Patterson-Fourier diagram shows the trigonal symmetry of the 

 crystal lattice in a most instructive way. 



The moment the crystalloids are removed from the mother liquor^ 

 however, and are exposed to the air, they denature and produce only 

 powder diagrams. Although they retain their crystallographic shape 

 outwardly, apparently the internal regular crystal lattice order can 

 only exist for just so long as the solvent is distributed between the 

 macromolecules . 



It would seem that there is some relationship between globular 

 reserve and fibrillar frame proteins, notwithstanding the great 

 differences between them in point of solubility and the morphology 

 of the molecular elementary units, for Astbury, Dickinson, and 

 Bailey (1935) succeeded in producing filaments and films from the 

 seed globulin edestin and from egg albumin which, when elongated,, 

 exhibit the ^-keratin type of fibre diagram. Astbury therefore assumes 

 the presence of folded polypeptide chains in the crystalloids of the 

 reserve proteins, as represented in Fig. 165. In this way certain self- 

 contained isodiametric areas might be imagined, corresponding ap- 



