yi PREFACE 



seeking to identify the nature of the Hght-emitting molecule in living 

 cells is as critically evaluated as present information permits. 



The biochemical approach is emphasized in the next four papers, 

 which deal with the luminescent systems of Cypridina, the firefly, and 

 luminous bacteria. Tsuji, Chase, and Harvey discuss the most recent 

 chromatographic and electrophoretic experiments which have resulted 

 in highly purified Cypridina luciferin and have made it possible to 

 show that such preparations exhibit not only fluorescence but also, 

 in certain solvents, phosphorescence. Changes in the absorption spec- 

 trum resulting from oxidation, or from changes in pH, are described. 

 Data on the infrared absorption spectrum are contributed in the dis- 

 cussion by Mason. Products of hydrolysis furnish a partial clue as to 

 the nature of the luciferin, although the structure of the molecule 

 remains to be established. 



The biochemistry of firefly luminescence, including the most recent 

 advances, is summarized in the paper by McElroy and Hastings. The 

 role of activators, including ATP, pyrophosphate, and Mn or Mg ions, 

 as well as the action of inhibitors and the influence of variations in 

 concentration of reactants, variations in temperature, pH, oxygen ten- 

 sion, and other factors, is considered in detail. On the basis of the 

 available evidence, a reaction scheme is proposed to account for the 

 control of either steady state or flashing luminescence in both the intact 

 organ and in extracts of the firefly. Additional data on the chemical 

 and physical properties of firefly luciferin are contributed in a brief 

 paper by Strehler, including evidence, from mass spectroscopy of 

 chromatographically purified luciferin, suggestive of a dipyrimidopy- 

 razine nucleus. 



The biochemistry and mechanisms controlling the emission of light 

 in extracts of luminous bacteria is treated at some length by Strehler, 

 who recently succeeded in obtaining easily visible luminescence in 

 cell-free preparations of these organisms. The roles of flavine mono- 

 nucleotide, coenzyme I, and a long chain aliphatic aldehyde, all of 

 which appear to be necessary for a long-lasting, bright luminescence 

 of the enzyme preparation, are discussed. A detailed reaction scheme 

 postulating terminal reactions with a peroxide is presented to account 

 for the available data, including the effects of temperature and hydro- 

 static pressure. Considerations bearing on this scheme, in particular. 



