Mechanistic Insight into Marine Bioluminescence: Photochemistry of the Chemiexcited Cypridina (Sea Firefly) Lumophore

Abstract

Cypridina hilgendorfii (sea firefly) is a bioluminescent crustacean whose bioluminescence (BL) reaction is archetypal for a number of marine organisms, notably other bioluminescent crustaceans and coelenterates. Unraveling the mechanism of its BL is paramount for future applications of its strongly emissive lumophore. Cypridina produces light in a three-step reaction: First, the cypridinid luciferin is activated by an enzyme to produce a peroxide intermediate, cypridinid dioxetanone (CDO), which then decomposes to generate excited oxyluciferin (OxyCLnH*). Finally, OxyCLnH* deexcites to its ground state along with emission of bright blue light. Unfortunately, the detailed mechanism of the critical step, the thermolysis of CDO, remains unknown, and it is unclear whether the light emitter is generated from a neutral form (CDOH) or anionic form (CDO(-)) of the CDO precursor. In this work, we investigated the key step in the process by modeling the thermal decompositions of both CDOH and CDO(-). The calculated results indicate that the decomposition of CDO(-) occurs via the gradually reversible charge transfer (CT)-initiated luminescence (GRCTIL) mechanism, whereas CDOH decomposes through an entropic trapping mechanism without an obvious CT process. The thermolysis of CDO(-) is sensitive to solvent effects and is energetically favorable in polar environments compared with the thermolysis of CDOH. The thermolysis of CDO(-) produces the excited oxyluciferin anion (OxyCLn(-)*), which combines with a proton from the environment to form OxyCLnH*, the actual light emitter for the natural system.

Theoretical Study of Dinoflagellate Bioluminescence

“…That indicates that the 1 ( π , π *) excited state is the possible fluorescent state or bioluminescent state in vivo . This is consistent with our previously studied bioluminescence systems, firefly , jellyfish , Obelia , Cypridina and bacteria , and their bioluminescent states are all 1 ( π , π *) state. The light emitter of dinoflagellate bioluminescence may be luciferin or its derivatives with the same chromophore.…”

Solvent viscosity influence on the chemiexcitation efficiency of inter and intramolecular chemiluminescence systems

“…30 In this work, the results obtained with the intramolecular CIEEL system induced 1,2dioxetane decomposition were compared with the highly efficient peroxyoxalate reaction, which is believed to involve an intermolecular CIEEL mechanism in its chemiexcitation step. [34][35][36][37][38][39][40][41][42][43] On the basis of the above discussion, we compare here the effect of the medium viscosity on the chemiexcitation quantum yields of the induced decomposition of 1,2-dioxetanes (highly efficient intramolecular CIEEL system) and the catalyzed decomposition of diphenoyl peroxide and a 1,2dioxetanone derivative (model systems for the intermolecular CIEEL mechanism, despite their low efficiency). [34][35][36][37][38][39][40][41][42][43] On the basis of the above discussion, we compare here the effect of the medium viscosity on the chemiexcitation quantum yields of the induced decomposition of 1,2-dioxetanes (highly efficient intramolecular CIEEL system) and the catalyzed decomposition of diphenoyl peroxide and a 1,2dioxetanone derivative (model systems for the intermolecular CIEEL mechanism, despite their low efficiency).…”

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.…”