214 LIGHT AND LIFE 



aldehyde increases the efficiency of the luminescent oxidation. The 

 evidence indicates that it becomes boimd to the luciferase along 

 with two molecules of flavin phosphate, and possibly furnishes part 

 of the energy of excitation by undergoing peroxidation (8, 36, 44, 

 46, 47). With the essential reactants in limiting concentrations, the 

 total amount of light emitted is proportional to the amount of alde- 

 hyde added, with an efficiency of about 20 molecules of aldehyde used 

 per quantum of light emitted, Avhile the flavin is not used up (8) . In 

 the sustained luminescence which results when DPNH is added to 

 the above components, the efficiency with respect to DPNH is only 

 about 1 quantum of light per 2,800 molecules, a result in keeping 

 with the influence of variations in temperature and hydrostatic pres- 

 sure on the system, to the effect that most of the hydrogen transfer 

 from DPNH is via non-luminescent pathways (45) . 



Specificities and Relationships of Different Systems 



The Cypridina, firefly, and bacterial systems clearly differ from 

 one another biochemically. Because of the known differences in 

 these systems, together with wide variations in the emission spectrum 

 among different types of luminescent organisms, (or even in the 

 same animal, as witnessed by the red and green luminescence of the 

 "railroad worm Phrixothrix (27)), as well as the random occurrence 

 of luminescence on the evolutionary scale of organisms, and finally, 

 the failure of innumerable attempts to obtain luminescence in "cross- 

 reactions" between the luciferin contained in extracts of one type 

 with the luciferase in extracts of a different type of organism, the 

 more or less prevalent view has arisen that essentially all luminescent 

 systems are chemically unlike (27, 28) . 



Other considerations, however, do not lend support to this view. 

 In the first place, almost no information is available concerning the 

 actual chemical structure of different luciferins, and generalizations 

 based on indirect evidence are not strictly reliable. Moreover, only 

 slight modification of a chemiluminescent or fluorescent molecule 

 is sometimes sufficient to effect wide differences in emission spectra, 

 e.g., the wavelength of maximum chemiluminescene intensity of 3- 

 nitrophthalhydrazide is 4,020, while that of 3-acetyl carbaminophthal- 

 hydrazide is 4,625 A, and the fluorescence peak of 3-aminophthal- 

 hydrazide occurs at slightly over 4,000 A in O.OI N KOH, but at over 

 5,000 A in 0.1 N KOH (6). Thus, it is unnecessary to postulate 

 totally different types of compounds to account for variations in 

 emission spectra. The random distribution of the property of bio- 



