Theoretical Study of Dinoflagellate Bioluminescence

Abstract

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.

Investigation of the Dinoflagellate Bioluminescence Mechanism: Chemically Initiated Electron Exchange Luminescence or Twisted Intramolecular Charge Transfer?

“…The mechanisms of LCF catalysis proposed herein (Figure ) are in contrast to the mechanism involving Dexter energy transfer that was proposed in the recent theoretical study of dinoflagellate bioluminescence by Wang and Liu . In that study, the experimental observation that LH 2 (as opposed to LO) is fluorescent, with a λ em value similar to the bioluminescence emission maximum, was confirmed using TD‐DFT .…”

“…Likewise, the calculated vertical emission wavelengths from the first excited state of the E and Z isomers of LH 2 ( λ em =405 nm and 415 nm, respectively) are smaller than the experimental fluorescence λ max em value. A similar underestimation of the experimental absorption and emission wavelengths of LH 2 by 50–70 nm was obtained using the Coulomb‐attenuated hybrid exchange‐correlation functional (CAM‐B3LYP) in a very recent computational investigation of dinoflagellate bioluminescence . In that study, the spectroscopic properties of a slightly larger model of LH 2 and LO were examined and a mechanism of LCF catalysis involving Dexter energy transfer was proposed, wherein an excited state LO intermediate transfers energy to a second LH 2 molecule (or an analogue thereof), which serves as the bioluminophore .…”

“…As imilar underestimation of the experimental absorption and emission wavelengths of LH 2 by 50-70 nm waso btained using the Coulomb-attenuated hybrid exchange-correlation functional (CAM-B3LYP) in av ery recent computational investigation of dinoflagellateb ioluminescence. [28] In that study,t he spectroscopic properties of as lightly larger model of LH 2 and LO weree xamined and am echanism of LCF catalysis involving Dexter energy transfer was proposed, wherein an excited state LO intermediate transfers energy to as econd LH 2 molecule (or an analogue thereof), which serves as the bioluminophore. [28] This proposal is based on the factt hat, unlike other bioluminescent systems, the LH 2 substrate, rather than the LO product, is fluorescent.…”

Photoluminescence Rainbow from Coelenteramide—A Theoretical Study

“…The Coulomb‐attenuated hybrid exchange‐correlation functional CAM‐B3LYP is employed in the present calculations. As a long–range‐corrected hybrid exchange‐correlation functional, CAM‐B3LYP performs well in predicting charge‐transfer excitations and has been widely used to study the mechanism and spectral properties of many bioluminescence and chemiluminescence phenomena . The effect of the size of basis set on geometries, absorption maxima ( λ max ) and fluorescence wavelengths ( λ F ) was tested.…”

Theoretical Insight into the Emission Properties of the Luciferin and Oxyluciferin of Latia

“…Obviously, identification of the light emitter stands as one of the most important problems toward better understanding of the BL. In most BL systems, the light emitter is the excited‐state OxyLuc, and this is the case with fireflies and Cypridina , and in a few cases, it is the excited‐state Luc, as is the case with the dinoflagellates . However, according to the experimental results, in the BL of Latia , neither the Luc nor the OxyLuc is fluorescent .…”