182 BIOCHEMISTRY OF FIREFLY LUMINESCENCE 



purified components are initially mixed there is, at first, a bright flash 

 of light which then rapidly declines to the low baseline level as 

 inactive complex is formed. Results will be discussed below which 

 indicate that the complexing reaction will occur under anaerobic con- 

 ditions. Under these circumstances, however, it can be shown that an 

 active intermediate accumulates which rapidly decomposes upon re- 

 admission of oxygen to give a brilliant flash of light. Additional evi- 

 dence will be discussed which suggests that inorganic pyrophosphate 

 and triphosphate stimula':e light production by splitting the inactive 

 complex to form a higher concentration of the active intermediate. 



Effect of Oxygen Tension on the Light Reaction 



When a reaction mixture that has reached the basal steady-state 

 intensity is deaerated with purified hydrogen, the light goes out within 

 a minute or two after deaeration is begun (Hastings, McElroy, and 

 Coulombre, 1953). When air or oxygen is readmitted to this solution, 

 an extremely bright flash of light appears with a maximum intensity 



Fig. 15. Photograph of the oscilloscope screen showing the flash reaction. Total 

 time of sweep, 7 seconds (Hastings, McElroy, and Coulombre, 1953). 



between 50 and 75 times the steady-state level. The flash is very brief, 

 of about 1 second duration, and quickly returns to the steady-state 

 level. Figure 15 shows an oscilloscope photograph of such a flash. In 

 some cases the curve is symmetrical; in others the rise is somewhat 

 steeper than the fall. The latter cases are attributed to experimental 

 conditions where the oxygen was admitted particularly rapidly. The 

 flash, as observed in these experiments, had a duration of the order 

 of from 1 to 3 seconds. The above procedure may be repeated as 

 often as is desired, using the same reaction mixture, and the same 

 qualitative result is obtained. In practice the luminescence becomes 

 very dim after 10 to 20 minutes, as a result of surface denaturation of 



