F. I. TSUJI, A. M. CHASE AND E. N. HARVEY 143 



erin are definitely yellowish to the eye but become colorless in excess 

 of sodium hydroxide. The disappearance of the visible absorption 

 band at 465 mfi is responsible for this color change and even more 

 striking changes occur in the ultraviolet region of the spectrum. If 

 the solution is immediately made acid again, the yellow color partly 

 returns. There are evidently acid-base changes in absorption, compli- 

 cated by rapid oxidation changes especially marked in alkahne solu- 

 tion, and these will now be described. 



250 300 350 400 450 500 550 250 300 350 400 450 500 550 

 WAVELENGTH I N ITl JU 



Fig. 4. In A, the dash hne shows the absorption spectrum of a luciferin solution 

 adjusted to pH 13 soon after having been prepared in 0.1 N hydrochloric 

 acid and before significant oxidation has occurred in the acid solution. An 

 unstable absorption peak appears at 380 mix, which shifts rapidly toward 

 shorter wavelengths. The dotted line curve shows the spectrum of the same 

 solution after having been readjusted to pH 1.0. In B, the dash line represents 

 the spectrum of a luciferin solution adjusted to pH 13 after having stood 

 exposed to air at pH 1.0 for twelve days, until presumably the luciferin 

 was completely oxidized. The alkaline spectrum, which is relatively stable, 

 shows a new absorption peak at 330 m/i. See the text for details and dis- 

 cussion. 



As shown in Fig. 3, a freshly prepared 0.1 N hydrochloric acid solu- 

 tion of luciferin, isolated by paper chromatography, has a pronounced 

 absorption peak at 265 m^t and a shoulder at about 310 m/x. There is 

 no specific absorption in the long-wavelength region of the ultraviolet. 

 On adjusting the pH of such a solution from 1.0 to 13 with sodium 



