238 BIOCHEMISTRY OF BACTERIAL LUMINESCENCE 



trons are already displaced toward the excited level, this thermally 

 derived energy would be available for the formation of the excited 

 state, in addition to the energy liberated on reaction. 



Another possible mechanism involves the formation of an unstable 

 oxidizing free radical (e.g., enzyme • RCHO • HO2 • ) at the expense of 

 thermal energy. Formation of such a compound might represent a 

 major portion of the observed activation energy and, upon reaction 

 with a flavin, give rise to a much more exergonic step reaction than 

 would be indicated by the overall nonluminous process. The energy 

 thus derived would in all likelihood be sufficient to excite the fluores- 

 cent molecule. 



Unfortunately, evidence is not at present available to assay critically 

 the merits, faults, or pertinence of the various possibilities discussed. 

 The biochemical evidence can, in a large part, be molded into a 

 consistent picture. Whether the physical objections to the biochemical 

 deductions are fatal, must be resolved by further experiment. 



ACKNOWLEDGMENTS 



The author wishes to point out that a large portion of this work would 

 not have been carried out so promptly and efficiently were it not for the 

 able collaboration of Mr. Milton CoiTnier of the Oak Ridge National Labora- 

 tory Biology Division. Dr. John R. Totter and Dr. William A. Arnold are 

 to be thanked for invaluable assistance and advice during the course of 

 the work. The latter and Dr. James Franck, of the University of Chicago, 

 contributed liberally of time and advice on certain points in the manuscript 

 as did Dr. Frank Johnson, of Princeton University, although the ideas ex- 

 pressed do not necessarily coincide with theirs. 



Much of the work with bacterial extracts on which this review is based 

 was perfoiTned at the Biology Division of the Oak Ridge National Labora- 

 tory and in collaboration with Drs. E. Newton Harvey, Joseph Chang, and 

 Frank Johnson of Princeton. 



References 



Chance, B., E. N. Harvey, F. H. Johnson, and G. Millikan. 1940. The 

 kinetics of bioluminescent flashes. A study in consecutive reactions. /. 

 Cellular and Comp. Phijsiol., 15, 195-215. 



Cormier, M. J., and B. L. Strehler. 1953. The identification of KCF: Re- 

 quirement of long-chain aldehydes for bacterial extract luminescence. 

 ;. A771. Chem. Soc, 75, 4864. 



