148 



CHEMISTRY OF CYPRIDINA LUCIFERIN 



was demonstrated in the last section (see Fig. 3, for example). The 

 fact that, even in the freshly prepared acid luciferin solution the 

 fluorescence is only slight, compared with that of such compounds as 

 riboflavin, may be in part due to absence of pronounced absorption 

 bands in the near ultraviolet region of the spectrum (i.e., 330-400 

 m/t). On the other hand, quenching phenomena may be involved, as 

 in the case of flavins combined with protein (see Weber, 1950). 



TABLE I 



Fluorescence of Chromatographed Luciferin and Completely Oxidized Luciferin 



" The color returns to a less intense yellow on immediate neutralization. 



' On first making alkaline, the yellow fluorescence is relatively more intense than 

 after standing exposed to air for 15 minutes. 



" Studied in a nonfluorescent cellophane tube after 3 weeks when no light appeared 

 on mixing with luciferase. 



When a freshly prepared 0.1 N hydrochloric acid solution of paper 

 chromatographed luciferin is made alkaline (pH 13) with sodium 

 hydroxide and is then irradiated with the Wood light, there is at first 

 a slight enhancement of the fluorescence compared with that given 

 by the freshly prepared acid solution. The fluorescence rapidly de- 

 •creases, however, as the alkaline solution stands, and becomes rela- 

 tively faint. This effect can perhaps be explained by the changes 

 which occur in the absorption spectrum of such a luciferin solution 

 upon adjusting its pH to 13. It will be recalled that a prominent, new 

 absorption band appears at 380 mix when such a luciferin solution is 



