Systematic Theoretical Investigation on the Light Emitter of Firefly

S.-F. Chen (1) , Y.-J. Liu (1) , Isabelle Navizet (2) , N. Ferre (3) , W.-H. Fang (1) , R. Lindh (4)

1 Key Laboratory of Theoretical and Computational Photochemistry
2 MSME - Laboratoire de Modélisation et Simulation Multi Echelle
3 LCP - Laboratoire Chimie Provence
4 Department of Chemistry-Angstrom, the Theoretical Chemistry Programme

This is a systematic theoretical investigation on all the possible light emitters of firefly using a multireference method. Six chemical forms of oxyluciferin (OxyLH(2)) 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-OxyLH(2), keto-OxyLH(2), 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 (S(1)) of phenolate-keto-OxyLH(-).

S.-F. Chen, Y.-J. Liu, Isabelle Navizet, N. Ferre, W.-H. Fang, et al.. Systematic Theoretical Investigation on the Light Emitter of Firefly. Journal of Chemical Theory and Computation, 2011, 7 (3), pp.798--803. ⟨10.1021/ct200045q⟩. ⟨hal-00692848⟩