Theoretically obtained insight into the mechanism and dioxetanone species responsible for the singlet chemiexcitation of Coelenterazine

• Type: Article in International Scientific Journal
• Date: 2017

Authors

Min, CG (Author) Other; Ferreira, PJO (Author) Other; da Silva, LP (Author) FCUP

Journal

Title: Journal of Photochemistry and Photobiology B: Biology

Vol. 174

Pages: 18-26

ISSN: 1011-1344

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 26 Citations

Scopus - 27 Citations

Other information

Authenticus ID: P-00N-31H

DOI: 10.1016/j.jphotobiol.2017.07.012

Abstract (EN): Coelenterazine is a widespread bioluminescent substrate for a diverse set of marine species. Moreover, its imidazopyrazinone core is present in eight phyla of bioluminescent organisms. Given their very attractive intrinsic properties, these bioluminescent systems have been used in bioimaging, photodynamic therapy of cancer, as gene reporter and in sensing applications, among others. While it is known that bioluminescence results from the thermolysis of high-energy dioxetanones, the mechanism and dioxetanone species responsible for the singlet chemiexcitation of Coelenterazine are not fully understood. The theoretical characterization of the reactions of model Coelenterazine dioxetanones showed that efficient chemiexcitation is caused by a neutral dioxetanone with limited electron and charge transfer, by accessing a region of the PES where ground and excited states are nearly-degenerated. This finding was supported by calculation of equilibrium constants, which showed that only neutral dioxetanone is present in conditions associated with bioluminescence. Moreover, while cationic amino acids easily protonate amide dioxetanone, anionic ones cannot deprotonate the neutral species. These results indicate that, contrary to existent theories, efficient chemiexcitation can occur with significant electron and/or charge transfer. In fact, these processes can be prejudicial to chemiexcitation, as anionic dioxetanones showed a less efficient chemiexcitation despite the occurrence of significant electron and charge transfer.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9