314 BIOLOGICAL EFFECTS OF RADIATION 



(39, 40) found a fall. When fibrinogen is sensitized with hematopor- 

 phyrin and radiated with visible light, it becomes more soluble and after 

 radiation is not coagulated by thrombin, does not coagulate on heating, 

 and does not flocculate on dialysis. This increased solubility after 

 radiation is unique except for the fact that albumin radiated at 0°C., at 

 a pH > 5.4, no longer coagulates on heating. 



With these two exceptions it may be stated in general terms that all 

 proteins (albumins, pseudoglobulins, and euglobulins) are denatured by 



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ultra-violet radiation shorter than 3000 A at any pH, whether they are 

 radiated in oxygen or nitrogen. After denaturation they flocculate if 

 brought to the isoelectric point or on dialysis and are more readily 

 precipitated by salts, alcohol or heat. This denaturation is accompanied 

 by an increase in ultra-violet absorption, an increase in viscosity, a 

 decrease in surface tension, an increase in levorotation, and by the devel- 

 opment of a characteristic odor and a yellow color. The decrease in 

 affinity for water and the increase in absorption are more marked in 

 albumins. The increase in viscosity and decrease in surface tension are 

 more marked in globulins. 



THE EFFECT OF X-RAYS AND RADIUM RAYS ON PROTEINS 



Denaturation. — In the first investigation of the effect of radium on 

 proteins Hardy (24) found that globulin is turned to a jelly only when 

 it is negatively charged. This is apparently a direct effect on the nega- 

 tive colloid produced by the positive a-particles. The effect of beta and 

 gamma rays is to denature proteins irrespective of their charge. Fernau 

 (17 to 19) found that serum albumin and egg albumin remained clear 

 after seven hours' radiation but showed evidence of denaturation as they 

 were more easily precipitated by alcohol and the heat coagulation tem- 

 perature was lower. The solutions became opalescent after several 

 days' radiation and flocculated if radiated for still longer periods. Simi- 

 lar results were obtained with pseudoglobulin solutions. In subsequent 

 experiments (21) the process of denaturation was followed by covmting 

 the number of particles in a Tyndall cone of known depth by means of 

 an ultramicroscope. Pseudoglobulin from horse serum was exposed to 

 beta and gamma radiation by immersing a glass capsule containing 

 78 mg. of radium in the solution. There was no visible change in six 

 days, but after an exposure of one day there was a marked increase in 

 the number of particles counted under the ultramicroscope. 



Wels (59) and Wels and Thiele (62) used the ultramicroscope to 

 follow the denaturation produced in proteins by exposure to X-rays. 

 They radiated serum albumin and serum globulin in buffer solutions on 

 both sides of the isoelectric point. In serum albumin the increase in 

 the number of particles was only marked at the isoelectric point and fell 

 off rapidly at a higher or lower pH. Globulin solutions showed a large 



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