BERNARD L. STREHLER 211 



ment. It is hoped that discussion at this conference will deal critically 

 with those aspects of the work which we have handled unsatisfac- 

 torily because of limitations of time and background. 



Extraction of Luminescent System 



It had been noted repeatedly (Harvey, 1952; Korr, 1935) that the 

 luminescent powders obtained by a variety of quick-drying methods 

 will emit light when they are suspended in water. Similarly, in un- 

 published experiments performed in early 1951, Dr. Charles S. Shoup 

 and I were able to obtain light for a few minutes when we added 

 acetonized bacterial powders to water. Addition of boiled extracts did 

 not result in measurable effects once the luminescence had disap- 

 peared. However, with the possibility in mind that the oxidant rather 

 than 'luciferin" might be limiting, we added hydrogen peroxide to 

 the dark extracts and obtained considerable light. Further studies 

 indicated that one of the compounds responsible for this chemilumi- 

 nescence in the presence of peroxide is a flavin (Strehler and Shoup, 

 1953). 



Partly because of the press of other work and partly because of our 

 skepticism of the eventual success of further work, these powders re- 

 mained for nearly two years in a deep freeze before we again 

 attempted to extract the luminescent system. A systematic study was 

 again undertaken in the fall of 1952 with almost immediate success 

 (Strehler, 1953; Strehler and Cormier, 1953). The crucial finding from 

 our point of view was the fact that the duration of luminescence and 

 its restoration by added agents depended on the concentration of 

 powder used. Low concentrations were incapable of luminescing for 

 longer periods or of responding to added biochemical reagents, while 

 a tenfold increase in the ratio of powder to water sustained a con- 

 tinual luminescence and exhibited a "luciferin-luciferase" reaction. This 

 effect is illustrated in Fig. 1 while Fig. 2 illustrates the effect of dilu- 

 tion on the system. 



Nature of Diffusible Requirements 



DPNHo and FMN 



Once a sustained and renewable luminescence was attainable a 

 wide variety of shelf biochemical reagents were tested, including 



