w. D. Mcelroy and j. w. Hastings 



183 



the enzyme through bubbhng. The flash phenomenon is interpreted 

 as being due to the accumulation of an active intermediate which, 

 during the steady-state condition under aerobic conditions, is present 

 in only relatively low concentrations. The reaction of the active inter- 

 mediate with oxygen is an extremely fast reaction for upon the ad- 

 mission of oxygen to such a system this active intermediate is rapidly 

 utilized and gives rise to the flash. 



The second method for obtaining data concerning the relation 

 between oxygen concentration and light intensity is as follows. Instead 



0.1 0.2 0.3 04 5 

 OXYGEN CONCENTRATION- PERCENT 



Fig. 16. Relationship between light intensity and oxygen concentration (Has- 

 tings, McElroy, and Coulonibre, 1953). 



of deaerating the system after the steady-state period had been 

 reached, the system was equilibrated with various lowered oxygen 

 concentrations before initiating the reaction with the enzyme (lucif- 

 erase). The particular gas mixture was bubbled continuously, and 

 the light intensity was measured continuously after the luciferase was 

 added to start the reaction. Under control conditions, i.e., when air 

 is used for the equilibrating gas, the complexing is considered com- 

 plete within 234 minutes from the start of the reaction. In Fig. 16 

 the intensities observed at this time have been plotted with respect 

 to the oxygen concentrations under which the reaction had been 

 proceeding. When these data are compared with data obtained by the 



