EFFECT OF RADIATION ON PROTEINS 



313 



has been stated that radiated water contains hydrogen peroxide which 

 may produce oxidation even when free oxygen is not present. Kernbaum 

 (31 to 33) found H2O2 in water radiated with radium, probably as the 

 result of the reaction 2H2O = H2O2 + H2. However, both Kernbaum 

 and Tian (57, 58) state that this reaction does not take place in water 

 as the result of ultra-violet radiation unless very short wave-lengths 

 are used (probably shorter than 1700 A) and a very long radiation is 

 given. Oxidation as the result of the formation of hydrogen peroxide, 



2,500 



3,000 



4,000 



4,500 



3,500 o 



Wave Leng+h in A 



Fig. 2. — Change in absorption curve of egg albumin after ultra-violet radiation: (1) 

 egg albumin unradiated; (2) after radiation in O2; (3) after radiation in N2. (After J. P. 

 Becker and P. Szendro, PftUgers Archiv. Gesam. Physiol. 228: 755. 1931.) 



therefore, can hardly be a factor in the denaturation of proteins by 

 ultra-violet radiation. 



SENSITIZATION TO VISIBLE LIGHT 



Ordinarily proteins are denatured only by radiation shorter than 



o 



3000 A. In the presence of certain sensitizers, however, proteins are 

 denatured in visible light in the region of the absorption band of the 

 sensitizer (9). No investigations have been made to determine whether 

 oxygen is necessary for this reaction or not. Eosin, mercurochrome, and 

 a number of other dyes act as sensitizers. The most active sensitizer 

 in vivo is a -derivative of hemin, hematoporphyrin. An animal into 

 which it has been injected, when exposed to visible light, suffers from 

 extensive erythema and death may result, probably from a fall in blood 

 pressure due to extensive capillary dilatation. Howell (29) sensitized 

 fibrinogen to visible light with hematoporphyrin with very curious and 

 anomalous results. Ultra-violet radiation affects unsensitized fibrinogen 

 like other globulins, making it less soluble. Dreyer and Hansen (14) 

 found a rise in coagulation temperature in radiated fibrinogen and Mond 



