n. /). Md'J.noV AM) H. H. SELK.ER 



24 i 



LJ 



lOOi- 



90 



80 



70 



o 



£ 



— 50 



D 

 O 



40 



30 



20 



OXYLUCIFERIN 23 C 



(2) 



(5) 



460 544 



(4) 



OZ) 



460 544 



P 



H 4 



(4) 



(39) 



460 544 



P 



H 6 



(47) 



544 



P 



H 8 



(100) 



544 



pH 10 



X m^. 



348 



395 



460 



544 



61 6 



Fig. 20. Energy-level diagram of oxyluciferin absorption and fluorescence. The 

 solid dots represent peak absorption levels, the straight arrows represent internal 

 transitions, and the wavy arrows the emission of light whose wavelength in milli- 

 microns is given in the break of the arrow. The energies in kcal/mole correspond- 

 ing to these absorptions and emissions are given on the left ordinate. To show 

 the degree of overlap among the various levels, the approximate spectral distribu- 

 tions are plotted at the right of the figure. 



sponsible for the emission as contrasted with absorption. Thus the 

 intramolecular energy transfer is dependent upon the ionic species 

 present, which in tiun is a function of pH or, in the bioluminescence 

 case, upon the type of hydrogen-binding to the en/yme surface. This 

 intramolecular transfer efficiency is reflected in the fluorescence yield 

 of the luciferin and oxyluciferin molecules (Fig. 21) . These data 

 were obtained using the combination of a spectrophotofluorometer 



