242 



Mr. E. G. Young. 



the third crystalline product of ovalbumin, was exposed to the light of the 

 arc, and readings of the optical rotation were made frequently by removing 

 the tube to a Hilger polarimeter, with direct - vision spectroscope, and 

 observing the rotation (a E ) of the green line of a quartz mercury-vapour 

 lamp (X == 546'1 pfi). The instrument was accurate to - 01°. The observa- 

 tions were as follows : — 



Table V. — Effect of Illumination on Optical Eotation. 



Time of illumination. 



OE. 



He. 



minutes. 



o 



O 







0-79 



-36 -60 



10 



-81 



-37 -60 



30 



-84 



-38 -99 



45 



0-87 



-40-38 



105 



0-87 



-40 -38 



Concentration of ovalbumin, 2 '16 per cent. 

 aE = observed rotation. 

 [a] E = specific rotation. 



The results in Table V show that one of the effects of radiations of the 

 visible spectrum on pure crystalline ovalbumin is an increased power of 

 optical rotation. This increase in specific rotation was observed in a 

 solution that was entirely free from precipitate. A control tube of the 

 same length, and containing the same solution, was read consecutively with 

 the illuminated tube. It gave the same reading of 079 throughout the 

 experiment. 



An experiment to confirm the above observation was tried, using 

 crystalline serum albumin which had previously been exposed to sunlight 

 for 2 hours. The protein thus exposed was completely coagulated, for the 

 solution contained (NH 4 ) 2 S04 to the extent of 1 per cent. It is to be noted 

 that in this experiment the serum albumin of 3 - 46. per cent, strength was 

 completely coagulated inside of 2 hours, whereas ovalbumin in similar 

 concentration is only partially coagulated after 6 to 8 hours' exposure. 

 Now, the original unilluminated serum albumin had had a specific rotation 

 of — 78 - 60° by the green line of the mercury spectrum (A, = 5461 /a/a). 

 To the coagulum, with its supernatant liquid of about 100 c.c, were added 

 fifteen drops of concentrated ammonia, and complete solution was thus 

 brought about. This solution was examined in the polarimeter, and the 

 specific rotation of the serum albumin was found to have risen to almost 

 5° above that of the undenatured substance. Now, in the case of 

 unilluminated ovalbumin, I have been able to show that the specific 



