235 



The Coagulation of Protein by Sunlight. 

 By Elkid Gordon Young, Ramsay Memorial Fellow. 



(Communicated by Prof. F. G. Hopkins, F.E.S. Received July 6, 1921.) 

 (From the Biochemical Laboratory, Cambridge University.) 



It was first shown by Dreyer and Hanssen (1) in 1917 that ultra-violet light 

 produced a change in protein solutions which appeared to be similar to 

 coagulation by heat. They exposed various solutions in quartz chambers to 

 the light of a Bang lamp with iron and silver electrodes. Vitellin was found 

 most easily coagulated, while globulin, albumin and fibrinogen showed a 

 decreasing sensitivity to ultra-violet rays in the order mentioned. These 

 investigators also discovered that acids markedly increase the rate of precipita- 

 tion. Soret (2) had shown in 1883 that there are absorption bands in the 

 extreme ultra-violet region of the spectrum of various proteins, e.g., casein, 

 ovalbumin, mucin and globulin. Tyrosine likewise has this band in the 

 ultra-violet and Soret attributed to this constituent of the protein molecule 

 its power of absorbing ultra-violet rays. In this connection Harris and 

 Hoyt (3) carried out some interesting experiments on the protective power of 

 various substances for paramcecium cultures exposed to ultra-violet radiations. 

 They found that gelatin peptone, amino-benzoic acid, cystine, leucine and 

 especially tyrosine possessed the power of detoxicating ultra-violet rays when 

 placed as a thin layer of aqueous solution over paramcecium cultures under a 

 quartz-mercury lamp. The toxicity of the radiations for paramcecia or 

 protoplasm in general can be understood in the light of the discovery of 

 Dreyer and Hanssen coupled with that of Soret. 



From a physico-chemical standpoint Bovie (4) has published a study of the 

 coagulation of proteins by ultra-violet light. By exposing solutions of 

 crystalline ovalbumin, both dialysed and containing electrolytes, to the light 

 of a mercury-vapour lamp, he came to the conclusion that there were two 

 reactions involved in the coagulation of ovalbumin by ultra-violet light. The 

 first is a photochemical one with a low temperature coefficient, — denaturation ; 

 and the second is one with a higher temperature coefficient of two and is 

 dependent upon the electrolytes present, — coagulation. While using solutions 

 dialysed against tap water Bovie made the observation that the protein 

 appeared to become sensitive to light of longer wave-length, for his control 

 tubes in glass were slowly coagulated. 



Finally, from a medical point of view Schanz (5) has carried out a few 

 experiments on this phenomenon with egg-white, blood serum and pig lenses. 



s 2 



