312 BIOLOGICAL EFFECTS OF RADIATION 



found a decrease in the pH of distilled water after radiation and concluded 

 that the change in hydrogen ion concentration must be due to a change 

 in the solvent and not in the protein molecule and is probably due to 

 ionization of the water. As ultra-violet radiation does not liberate 

 electrons from water, this assumes an increase in electrolytic dissociation. 



Absorption. — The characteristic absorption bands of proteins in the 

 ultra-violet region (34, 35, 45, 56) were found by Spiegel-Adolf and 

 associates (28, 47, 48, 51-53) to undergo changes after radiation with 

 ultra-violet Hght. When enough acid or alkaU is added to prevent the 

 visible coagulation which occurs at the isoelectric point on radiation, 

 egg albumin, serum albumin, and serum pseudoglobulin all show increased 

 absorption after radiation, the change being more marked in albumins 

 than in globulins. After denaturation with ultra-violet radiation 

 albumins and pseudoglobulins have an extinction coefficient characteris- 

 tic of euglobulins in addition to the solubility of euglobulins. Spiegel- 

 Adolf notes that similar changes in absorption occur after denaturation 

 by radium but that after heat denaturation there is no increase in absorp- 

 tion except a slight effect in X < 2750 A. 



Becker and Szendro (3) measured the extinction coefficient of egg 

 albumin and ox serum albumin after radiation in O2 and N2. In both 

 cases there was an increase in absorption. When radiated in nitrogen, 

 the extinction coefficient increased with the maximum and minimum 

 still present at X 2800 and X 2500 A and the absorption limit was changed 

 from X 3100 to X 4000 A. When radiated in oxygen, the increase in 

 absorption was more marked, the maximum and minimum disappeared, 

 and there was absorption starting at 4000 A and increasing steadily 

 in going to shorter wave-lengths (see Fig. 2). Spiegel- Adolf (48) also 

 noted the fact that proteins show increased absorption after radiation 

 in either nitrogen or oxygen and concluded that light denaturation is 

 not an oxidation. The curves given in Fig. 2, however, show some 

 difference in the changes taking place in oxygen and nitrogen. 



It has been suggested that the increased absorption in light-denatured 

 albumin is due to a change in degree of dispersion of the protein, but as 

 increased absorption is also evident in the ultra-filtrate from radiated 

 proteins (especially when radiated in O2) it is probably not due to aggre- 

 gation alone but to some more fundamental change in the protein 

 molecule. 



Fluorescence.— W els (59, 60) and Becker and Szendro (3) have shown 

 that after radiation there is an increase in fluorescence of proteins, the 

 fluorescent radiation having a maximum at X 3600 to 3700 A. 



Oxygen a Factor. — Harris (25 to 27) found that plasma takes up oxygen 

 during radiation, but the fact that changes in solubility and extinction 

 coefficients have been found to take place when proteins are radiated in 

 nitrogen (48) indicates that denaturation is not due to an oxidation. It 



