F. I. TSUJI, A. M. CHASE AND E. N. HARVEY 159 



with a water solution of luciferin for one-half hour, the yellow color 

 of luciferin is replaced by a pink color and luminescence is markedly 

 decreased when luciferase is now added to the solution. In answer to 

 the second part of your question, we have not tested for disulfide 



groups specifically. 



Dr. Mason: Is it possible to estimate the concentration of solute in 

 the solutions with which you measured your absorption spectra and 

 to compare the concentrations with those of the solutions of Ander- 

 son's luciferin with which you and Brigham measured your earlier 

 spectra? 



Dr. Chase: Because luciferin in minute amounts was eluted from 

 filter paper and then finally dissolved in very small volumes of hydro- 

 chloric acid for measurement of the absorption spectrum, it was not 

 possible actually to determine the weight of the solute used in the 

 more recent studies. In the measurements of Chase and Brigham 

 (1951), where larger amounts of material were involved, weighing of 

 solid residues was possible and the actual concentration of solute 

 could therefore be determined. It amounted to about 0.02 mg of dry 

 material per milliliter of solution. 



Assuming that the absorption spectrum which has been presented 

 really represents luciferin, it is possible, of course, to estimate con- 

 centrations from relative extinction values. If this is done, the con- 

 centration of solute used in the present measurements would be 

 approximately three times that used in those reported by Chase and 

 Brigham (1951; Fig. 2, p. 532, and Fig. 3, p. 534). 



