Theoretical photodynamic study of the photoprotolytic cycle of firefly oxyluciferin

Luís Pinto Da Silva, Ron Simkovitch, Dan Huppert, Joaquim C.G. Esteves Da Silva*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Firefly oxyluciferin presents a pH-sensitive fluorescence in aqueous solutions. Its fluorescence spectra are composed of two green peaks at different pH values, despite the enolate anion being the only emitter. A computational approach was used to further elucidate the photoprotolytic cycle of oxyluciferin and investigate its pH sensitivity. It was found that oxyluciferin forms π-π stacking complexes both in the ground and excited states, at basic and acidic/neutral pH. However, at different pH values, these complexes adopt a different conformation, which explains the lower energy of the emission at acidic/neutral pH, in comparison with the emission at basic pH. A pH-sensitive fluorophore: Different conformations of the π-π stacking complex of the excited-state enolate species of firefly oxyluciferin lead to pH-sensitive fluorescence. This means that the enolate anion possesses different emission energies at acidic/neutral and basic pH.

Original languageEnglish
Pages (from-to)2711-2716
Number of pages6
Issue number12
StatePublished - 26 Aug 2013


  • complexes
  • enolate species
  • firefly oxyluciferin
  • pH-sensitive fluorescence
  • photoprotolytic cycle


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