Abstract
A luminous squid, Symplectoteuthis oualaniensis, emits blue light, and its photoprotein has been named as symplectin. The luminous substrate of symplectin is dehydrocoelenterazine (DCL) as natural chromophore. A synthetic chromophore, 2,4-difluoro-dehydrocoelenterazine (2,4-diF-DCL), was found to emits 2 times bioluminescence light amount comparing to natural form chromophore (DCL). The exchange of chromophore between 2,4-diF-DCL and DCL in symplectin might happen during incubation at pH 6. To prove the exchange of the chromophores, several diF-DCL analogs with modification at 8-position (methoxyphenyl and thiophene) were synthesized. These analogs have one more conjugated system at the 8-position resulting in red-shift in UV-Vis absorbance, fluorescence emission, chemiluminescence and bioluminescence wavelength. In this study, the characteristics of DCL analogs and other compounds which are producible in symplectin luminescence process were examined. With these data from authentic samples, chromophore exchange in symplectin could be monitored and percentage of exchange could be estimated.