Synthesis of 13C-Dehydrocoelenterazine and NMR Studies on the Bioluminescence of a Symplectoteuthis Model

The bioluminescence of luminous squid (Symplectoteuthis oualaniensis) is presumed to be initiated by the addition of the sulfhydryl residue of a photoprotein to dehydrocoelenterazine (DCL). To clarify this step, a novel synthetic route was established to label DCL with 13C. Dithiothreitol (DTT) and glutathione (GSH) were used as photoprotein models. The addition of DTT and GSH to 13C-labeled DCL gave luminous chromophores. Its structures were confirmed by NMR and MS spectrometry. The DTT adduct emitted light under alkaline condition to produce an oxidized compound. Thus we succeeded in modeling the bioluminescence of a photoprotein with DTT.