\V. D. MCELROY AND J. \V. HASTINGS 8l 



LUMINESCENT FLASHES IN VITRO 



Flashes have also been observed in the /// vitro system. The requirements for 

 light emission, as previously reported (7), are as follows: luciferase, luciferin, 

 Mg"*^, adenosine triphosphate (ATP) and oxygen. If a reaction mixture con- 

 taining these components is made anaerobic by bubbling hydrogen the lumi- 

 nescence ceases. When o.xygen is readmitted a bright flash, which was called 

 the 'oxygen' flash, occurs (5). This is the result of the accumulation under 

 anaerobic conditions of an intermediate which, when oxygen is admitted, is 



Fig. I. Normal flash of Pliotinus 

 pyralis. Sweep lime, 0.5 second. 



Fig. 2. Pseudoflash in Pliotinus py- 

 ralis. The firefly was placed in '2% oxy- 

 gen and after 2 minutes air was admitted. 

 The resulting flash was recorded as shown. 

 Sweep time, 4 seconds. 



rapidly oxidized with light emission. A recording of an oxygen flash is shown 

 in figure 3. It is evident that this flash is comparable to the pseudoflash of the 

 intact firefly. Moreover, both occur under essentially comparable conditions. 

 Although the oxygen flash provides a model mechanism for normal flashing, 

 the duration of the o.xygen flash is much longer than the normal flash. We have 

 recently attempted to experimentally change the duration of the oxygen flash. 

 Variations in the concentrations of luciferase, luciferin, ATP and Mg++ have 

 no effect upon the duration. The substitution of Mn"^ for Mg"^ results in a 

 flash having a slightly longer duration. In going from the anaerobic to the 

 aerobic condition, the use of air in place of oxygen also results in a flash of a 

 longer duration, particularly with respect to the rise time. When oxygen con- 



