title: Systematic Theoretical Investigation on the Light Emitter of Firefly.
abstract: This is a systematic theoretical investigation on all the possible light emitters of firefly using a multireference method. Six chemical forms of oxyluciferin (OxyLH2) molecules/anions were studied by a multistate complete active space second-order perturbation (MS-CASPT2) method in vacuum and dimethyl sulfoxide. The calculated results and subsequent analysis excluded enol-OxyLH2, keto-OxyLH2, and enolate-OxyLH(-) as possible light emitters. The remaining three candidates, phenolate-enol-OxyLH(-), phenolate-keto-OxyLH(-), and OxyL(2-), were further investigated in protein by a MS-CASPT2/molecular mechanics (MM) study to explain the natural bioluminescence of firefly. By comparison of the MS-CASPT2/MM calculated results of phenolate-enol-OxyLH(-), phenolate-keto-OxyLH(-), and OxyL(2-) with the experimental observation and detailed analysis, we concluded that the direct decomposition excited-state product of firefly dioxetanone in vivo and the only light emitter of firefly in natural bioluminescence is the first singlet excited state (S1) of phenolate-keto-OxyLH(-).
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
authors.forename: Shu-Feng
authors.initials: SF
authors.lastname: Chen
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Liu
authors.affiliation: Laboratoire Modélisation et Simulation Multi Echelle, Université Paris-Est , MSME UMR 8208 CNRS, 5 bd Descartes, 77454 Marne-la-Vallee, France.|Molecular Science Institute School of Chemistry, University of the Witwatersrand , PO Wits Johannesburg 2050 South Africa.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Navizet
authors.affiliation: Universités d'Aix-Marseille I, II, et III-CNRS UMR 6264: Laboratoire Chimie Provence, Equipe: Chimie Théorique, Faculté de St-Jérome, Case 521, 13397 Marseille Cedex 20, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferré
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
authors.forename: Wei-Hai
authors.initials: WH
authors.lastname: Fang
authors.affiliation: Department of Quantum Chemistry, The Ångström Laboratory , Uppsala University, P.O. Box 518, S-75120 Uppsala, Sweden.
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh