234 



THE EFFECT OF IONIZING RADIATIONS 



In spite of oxidation of thiol groups and of tyrosine residues, electro- 

 metric titrations have been of no aid, as no difference is observed be- 

 tween the control and the irradiated solutions. Measurements of electro- 

 phoretic mobilities were also of no help. Neither the areas nor the 



9.0 



X 10 A 



Fig. 15. Effect of x-ray irradiation on the absorption spectrum of bovine serum 



albumen, dissolved in 0.01 M fiuoroacetate buffer, pH 3.0. Abscissa: Wavelength in 



angstrom units; ordinate: molecular extinction coefficient X lO^E. 



mobilities of the protein solutions (serum albumin and globulin) were 

 altered significantly. Measurement of the sedimentation rate, however, 

 showed the presence of a second, faster-moving component when albumin 

 and globulin were irradiated at pH 3. It is quite possible that this is a 

 "dimerized" protein, the result of intermolecular union of two protein 

 molecules through their — S — S — bonds to give 

 Protein — S — S — Protein 



