F. I. TSUJI, A. M. CHASE AND E. N. HARVEY 149 



first made alkaline, but that on standing exposed to air, this band 

 rapidly shifts to a new maximum at about 355 m/t passing through the 

 region 365 m/* of great intensity in the Wood light (see Fig. 4A and 

 Fig. 5 ) . It is quite possible that the initial enhancement of the fluores- 

 cence when the solution is made alkaline is due to absorption in the 

 365-m/x region, and its subsequent diminished intensity is because of 

 the appearance of the 355-m^ band at a shorter wavelength where less 

 energy is emitted by the Wood light. 



On the other hand, an oxidized acid luciferin solution that is then 

 adjusted to pH 13 shows very faint fluorescence when irradiated with 

 the Wood hght. This seems quite understandable in view of the near 

 ultraviolet absorption spectrum of such a solution, as described in the 

 last section and shown in Fig. 4B. It will be recalled that such a 

 solution exhibits a rather narrow absorption band centering at about 

 330 millimicrons. Very little energy would be available at this wave- 

 length in the Wood light for fluorescence excitation. There does, 

 therefore, appear to be consistency between the results of the experi- 

 ments on fluorescence and those involving the absorption spectrum of 

 luciferin solutions under various conditions. A quantitative determina- 

 tion of the spectral distribution of the fluorescence of solutions of 

 paper chromatographed luciferin should be of value for the identifica- 

 tion of this compound and such measurements are contemplated. Of 

 course, it is always possible, as was stated earlier in this section, that 

 if luciferin is a chromopolypeptide, as suggested by Mason (l&52b), 

 the spectral distribution of fluorescence might be so affected by the 

 presence of the constituent amino acids as to make any interpretation 

 in terms of chemical structure extremely difficult. 



Hydrolysis of Luciferin 



Mason ( 1952b ) has reported that his alpha and beta kiciferins are 

 chromopolypeptides, on the following grounds: (1) alpha luciferin 

 was convertible to beta luciferin under certain experimental condi- 

 tions; (2) the infrared spectrum of beta luciferin indicated amide 

 bonds as they occur in peptides and cyclic ureides; (3) hydrolysis of 

 beta luciferin yielded a number of amino acids, including an unidenti- 

 fied ninhydrin positive substance and a yellow pigment; (4) beta 

 luciferin gave a positive N-chloroamide test (Rydon and Smith, 1952), 



