Theoretical Photodynamic Study of the Photoprotolytic Cycle of Firefly Oxyluciferin

Authors

  • Dr. Luís Pinto da Silva,

    1. Centro de Investigação em Química (CIQ-UP), Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687 4169-007 Porto (Portugal)
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  • Dr. Ron Simkovitch,

    1. Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978 (Israel)
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  • Prof. Dr. Dan Huppert,

    1. Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978 (Israel)
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  • Prof. Dr. Joaquim C. G. Esteves da Silva

    Corresponding author
    1. Centro de Investigação em Química (CIQ-UP), Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687 4169-007 Porto (Portugal)
    • Centro de Investigação em Química (CIQ-UP), Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, R. Campo Alegre 687 4169-007 Porto (Portugal)
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Abstract

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.

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