BENTLEY GLASS 855 



an efficieiuy ol 100 per teiit. I'licrc is no observed cliange in this 

 relation over the tempera line range ironi 3°C to 27 °C. Both the 

 tight biiuhng of the LHj-AMP and LAMP molecules to the enzyme, 

 and the lad that the lluorescente ol liiciterase overlaps the broad 

 absorption bands of lucilerin and oxyluciferin at neutral and alkaline 

 pH, seem alike relevant to the high quantum yield. Perhaps the 

 latter observation signifies that the enzyme-substrate complex forms 

 a resonant molecule able to transfer energy intramolecularly via 

 tryptophan residues until it is trapped at the site of emission. Physical 

 analogies of such a process are known. 



As pH is made more acid, the single yellow-green maximum of 

 the bioluminescent emission spectrum becomes weaker, and the maxi- 

 nuim emission changes to red. The quantum yield diminishes ma- 

 terially at the same time; it agrees rather well with the fluorescence 

 quantum yield at various pH's, except that the pK is at pH 7.4 in- 

 stead of pH 8.4. The previously noted inhibitory effect of inorganic 

 phosphate on the emission of light (effect of phosphate buffer) is 

 similar in nature to the effect of pH on the bioluminescence. That is, 

 even at neutral or alkaline pH, phosphate diminishes the yellow-green 

 emission maximum and causes the appearance of a red emission band. 

 These effects of phosphate and pH are furtlier evidence that the en- 

 zyme significantly influences the excited state. 



The mechanism of the bioluminescent reaction remains puzzling. 

 McElroy and Seliger rule out the possibility that there might be an 

 energy transfer from an excited product to the LH^-AMP molecule, 

 chiefly on grounds that it is the acid fluorescence of LHo-AMP that 

 is close to the bioluminescence emission whereas bioluminescence oc- 

 curs at neutral and alkaline pH values, and moreover that energy 

 transfer should vary with concentration whereas the flash height has 

 been shown to be proportional to enzyme concentration over an 

 enormous range. The data also eliminate the Linschitz type of 

 mechanism, which would involve a reaction of two LHo-AMP mole- 

 cules with oxygen in which one LHo-AMP is regenerated. It there- 

 fore becomes necessary to account for the approximately 60 kcal per 

 mole released in the oxidation of LHo-AMP by other means. Per- 

 oxidation alone is inadequate for this; but perhaps the formation of 

 a double bond in the oxyluciferin, contributing as much as 30 kcal 

 of resonance energy, plus the formation of hydrogen peroxide through 

 activation of oxygen in the reaction, would together be adequate. 



The dinoflagellat^ Cxonyaulox polyedra, another luminous organism, 

 has been studied by J. W. Hastings and V. C. Bode. The cell-free 



