ELIMINATION OF THE EFFECT OF CONTAMINATING CO2 IN THE 18O-LABELING OF THE CO2 PRODUCED IN BIOLUMINESCENT REACTIONS

Abstract— Although the mechanism of bioluminescent reactions in various species, such as fireflies, ostracod crustaceans ( Cypridina ), sea pansies ( Renilla ), and the deep-sea shrimp Oplophorus , are thought to involve dioxetanone intermediates, studies reported in the past from different laboratories have included widely different experimental results, most likely due to various factors including the effects of contaminating CO₂. With the improved technique employed in the present study, bioluminescent reactions of the firefly and Cypridina in ¹⁸O₂ gas resulted in an incorporation of over 75% of ¹⁸O into one oxygen of the product CO₂. with a reproducibility within a few per cent. When ¹³CO₂. instead of the product CO₂ of the bioluminescent reaction, was studied in an H₂¹⁸O medium, the exchange of one oxygen of ¹³CO₂ with H₂O was 64%. and the effect of contaminant CO₂ amounted to 1418% of the total CO₂. These results suggest that every molecule of CO₂ formed in the bioluminescent reactions of the firefly and Cypridina had intially contained 1 oxygen atom derived from O₂.