BERNARD L. STREHLER 207 



of the degree of unsaturation on an empirical basis. An attempt was 

 then made to derive structural formulas consistent with the remain- 

 ing empirical formulas, taking into account the other physical and 

 chemical evidence available. Although many different combinations 

 and permutations were attempted, only those arising from the dipyri- 

 midopyrazine nucleus could be fitted into the restrictions of the 

 empirical formulas. Subsequently, we synthesized several dipyrimido- 

 pyrazines and found, on the part of several of them, physical prop- 

 erties (such as fluorescence and absorption spectra) strongly remi- 

 niscent of luciferin, although the precise structure postulated on the 

 basis of the mass cracking pattern was not capable of synthesis by 

 the methods we employed. Figure 9 shows a structure for luciferin 

 consistent with the above data and a proposed scheme of pyrolytic 

 degradation to account for the major mass fragments observed. Note 

 that this cleavage involves the breaking only of single bonds. 



It should be emphasized that this structure is perhaps not the only 

 one which could be derived to fit the many properties observed. It 

 is, however, the only one we have been able to formulate which is 

 consistent with all the data available. Note that the calculated masses 

 are always one mass unit higher than the observed masses. If the 

 degradation product is a dimer through the sulfur grouping (disul- 

 fide) the rupture of the S — S bond would give an observed mass one 

 less than that calculated. 



ACKNOWLEDGMENTS 



The author wishes to express his appreciation to Dr. Russell Baldock of 

 the Oak Ridge National Laboratory for his generous contribution of time, 

 equipment, and assistance in certain phases of this work, to Mr. John Sites 

 for his collaboration in certain phases, and to Miss E. Brigham and Mr. B. 

 Bottoms for their expert assistance in portions of this work. 



References 



McElroy, W. D., and B. L. Strehler. 1949. Factors affecting the response of 

 the luminescent system to ATP. Arch. Biochem., 22, 420-33. 



