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Mechanistic Insight into the Chemiluminescent Decomposition of Cypridina Dioxetanone and the Chemiluminescent, Fluorescent Properties of the Light Emitter of Cypridina Bioluminescence

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posted on 2019-10-16, 18:36 authored by Chun-Gang Min, Qing-Bo Liu, Yan Leng, Carla M. Magalhães, Shao-Jun Huang, Chun-Xia Liu, Xi-Kun Yang, Luís Pinto da Silva
Cypridina bioluminescence has been increasingly used in bioimaging, bioanalysis, and biomedicine, due to high quantum yield and high signal-to-noise ratio. However, there is still no consensus regarding different aspects of the chemiluminescent mechanism of this system, which impairs the development of new applications. Herein, we have used a theoretical DFT and TD-DFT approach to (i) determine the identity of the dioxetanone species responsible for efficient chemiexcitation and (ii) identify the bioluminescent emitter and determine if light-emission occurs from the fluorescent or chemiluminescent state. Our results demonstrate that upon oxygenation of the imidazopyrazinone scaffold, a dioxetanone with a neutral amide group and a cationic guanidinopropyl group is formed. This species is efficiently chemiexcited (with no obvious charge transfer step) to the corresponding oxyluciferin with a neutral amide and cationic guanidinopropyl groups. After the “dark” chemiluminescent state, this oxyluciferin species is converted into a bright blue-emitting fluorescent state.

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