C. J. p. SPRUIT AND A. SPRUIT-VAN DER BURG 115 



tine (1941), which contained results of the resynthesis of luciferin 

 from its irreversible luminescent oxidation product. We were not in 

 a position to check the results reported and we may have attached 

 too much value to them. Taking all information together, van der 

 Kerk suggested that the compound whose absorption spectrum is the 

 inactivation spectrum had as part of its structure: 



COCH2OH 



From available data on the absorption spectra of naphthoquinones 

 (Macbeth et al, 1935) the assignment of a naphthoquinone structure 

 to the compound appeared justifiable. 



Although the situation at the moment no longer makes it especially 

 attractive to look for a relationship between the various forms of 

 bioluminescence, at that time it appeared promising to test this 

 hypothesis further by a study of the absorption spectra of naphtho- 

 quinones, and in this connection an attempt was also made to prepare 

 the compound mentioned by van der Kerk. Accepting his idea as a 

 working hypothesis, it appeared necessary to establish with more cer- 

 tainty the state of reduction of the hypothetical compound. Accord- 

 ing to van der Kerk, this should be the quinone form. This conclusion 

 he based mainly on the observation that several quinones (e.g., 

 2-methylnaphthoquinone ) are known to be photolabile. A closer anal- 

 ysis of the data, especially van der Kerk's experiments on the photo- 

 inactivation under low oxygen pressure, have convinced us that it is 

 much more likely that the reduced form of luciferin is the photolabile 

 component ( Spruit, 1949a ) . This is in harmony with the observation 

 that l,3,4-trihydroxynaphthyl-2-methylketone, a derivative of naphtho- 

 hydroquinone, is also photosensitive in the presence of low pressures 

 of oxygen (Spruit, 1947). It was therefore quite an exciting observa- 

 tion that the absorption spectrum of l,4-dihydroxynaphthyl-2-hydroxy- 



nV 



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