Theoretical Study of Dinoflagellate Bioluminescence

Dinoflagellates are the most ubiquitous luminescent protists in the marine environment and have drawn much attention for their crucial roles in marine ecosystems. Dinoflagellate bioluminescence has been applied in underwater target detection. The luminescent system of dinoflagellates is a typical luciferin-luciferase one. However, the excited-state oxyluciferin is not the light emitter of dinoflagellate bioluminescence as in most luciferin-luciferase bioluminescent organisms. The oxyluciferin of bioluminescent dinoflagellates is not fluorescent, whereas its luciferin emits bright fluorescence with similar wavelength of the bioluminescence. What is the light emitter of dinoflagellate bioluminescence and what is the chemical process of the light emission like? These questions have not been answered by the limited experimental evidence so far. In this study, for the first time, the density functional calculation is employed to investigate the geometries and properties of luciferin and oxyluciferin of bioluminescent dinoflagellate. The calculated results agree with the experimental observations and indicate the luciferin or its analogue, rather than oxyluciferin, is the bioluminophore of dinoflagellate bioluminescence. A rough mechanism involving energy transfer is proposed for dinoflagellate bioluminescence.