IONIZING RADIATIONS AND PROTEINS 



233 



ated with ultraviolet light, x-rays, and alpha rays. However, the mech- 

 anism of these changes is still unknown, and most of the early work 

 was done with impure solutions of protein. • 



Sanigar et al. (16) reported that irradiation of proteins with 29,000 r 

 of soft x-rays had no effect at all on the absorption spectrum. Contrary 



4 



Fig. 14. Effect of x-ray irradiation on the absorption spectrum of bovine serum 

 albumen (1 X 10~^ M) dissolved in water. Abscissa: Wavelength in angstrom units; 

 ordinate: molecular extinction coefficient X lO^E. (From Argonne National Labo- 

 ratory Quarterly Report, May-July 1949, p. 117.) 



to this report, we found that x-rays definitely affected the absorption of 

 light by protein solution even after irradiation with so small an x-ray 

 dose as 100 r. There was a general increase in the absorption of ultra- 

 violet light by the irradiated protein, the effect being greatest when 

 the protein was dissolved in water (Fig. 14) and least when the protein 

 was dissolved in acid solutions (Fig. 15) at a pH value below the iso- 

 electric point. These changes were less when the protein was irradiated 

 in the relative absence of oxygen. 



