The Coagulation of Protein by Sunlight. 



241 



buffer mixtures were employed, with a solution of ovalbumin three times 

 recrystallised. The time of exposure to very bright sunlight was 5 hours. 

 Ph determinations were made both before and after the exposure. The 

 results are recorded in Table IV. Each test consisted of 2 c.c. of buffer and 

 1 c.c. of ovalbumin solution. The concentration of ovalbumin in the 

 original solution was 2 per cent., and in the illuminated tubes was thus 

 about 0'7 per cent. Controls of tests 1 and 6 were prepared and kept in 

 the dark, with negative results. 



Table IV. — Effect of Ph Variations on Buffered Ovalbumin Solutions. 



Test. 



P 



Before. 



a. 



After. 



Result after exposure. 



At P H 4-8. 



1 



3-0 



3 5 



+ + + + 



+ + + + 



2 



4-0 



4-3 



+ + 



+ + 



3 



4-8 



5 '1 



+ 



+ 



4 



5 -4 



5-6 



opalescent 



+ 



5 



6-0 



5-6 





+ + 



6 



7-6 



6 5 





+ + + + 



Time of exposure to sunlight, 5 hours. 

 Concentration of ovalbumin, - 7 per cent. 



At the conclusion of the period of illumination, the tubes on the acid side 

 of P H 5 - 4 showed precipitates, the degree of which varied directly with the 

 hydrion concentration. The tubes on the alkaline side of Ph 5*4 were 

 merely opalescent. On acidulation to a Pn of 4'8, however, there appeared 

 precipitates, the degree of which varied directly with the hydroxyl ion 

 concentoation of the original solution. The comparison between heat 

 coagulation and light coagulation is thus brought even closer. Both acids 

 and alkalies increase the rate of the light reaction, and during this change 

 there is a removal of JI or OH ions from the solution depending upon its 

 reaction. 



Experiment 3. — What Physical Changes docs the Protein undergo before 



Fiocculation ? 



In order to discover whether some physical change in the solution 

 which was being subjected to light bombardment might be used as an 

 indication of the rate of the light reaction, several properties were investi- 

 gated. It was my intention to study the first reaction quite separately, if 

 possible, from the second, involving the fiocculation of the altered protein. 



(A) Optical Potation. — A 100-mm. tube, filled with the dialysed solution of 



