144 



CHEMISTRY OF CYPRIDINA LUCIFERIN 



hydroxide, a striking change occurs in the spectrum. Much of the far 

 ultraviolet absorption and practically all in the visible disappear and 

 a new peak is seen, maximal initially at about 380 m/x. This new peak 

 apparently shifts when the solution is exposed to air at room tempera- 

 ture and in about thirty minutes becomes stable, with a maximum at 

 about 355 m/x. The initial shift is quite rapid. 



These changes are shown in Figs. 4A and 5. In Fig. 4A, dash line 

 curve, the first measurement was made at 550 m/x., and the measure- 



0.6 



2 0.5 

 o 



10 

 V) 



2 0.4 



iD 



Z 

 < 



H0.3 



o 



_l 



' 0.2 



0.1 



0.0 



250 



300 



350 400 



WAVELENGTH 



500 



550 



450 

 IN m;j 



Fig. 5. An experiment designed specifically to show the rather rapid change in 

 the absorption spectrum of a freshly prepared 0.1 N hydrochloric acid solu- 

 tion of luciferin on adjusting the pH to 13 with sodium hydroxide. The most 

 prominent feature of the new alkaline spectrum is appearance of an absorp- 

 tion peak at 380 m/x, which rapidly shifts until it becomes stable at about 

 355 mn. The form of the stable alkaline spectrum is shown by the light solid 

 line curve. 



ments were then continued toward shorter wavelengths, to 365 m/x. 

 The next was then made at 400 m/x, after which they were again 

 continued in the direction of the shorter wavelengths. The rapid shift 

 of the 380-m;u absorption peak is quite evident from this sequence of 

 measurements. 



