A conical intersection controls the deactivation of the bacterial luciferase fluorophore

Samer Gozem, Ekaterina Mirzakulova, Igor Schapiro, Federico Melaccio, Ksenija D. Glusac*, Massimo Olivucci

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The photophysics of flavins is highly dependent on their environment. For example, 4a-hydroxy flavins display weak fluorescence in solution, but exhibit strong fluorescence when bound to a protein. To understand this behavior, we performed temperature-dependent fluorescent studies on an N(5)-alkylated 4a-hydroxy flavin: the putative bacterial luciferase fluorophore. We find an increase in fluorescence quantum yield upon reaching the glass transition temperature of the solvent. We then employ multiconfigurational quantum chemical methods to map the excited-state deactivation path of the system. The result reveals a shallow but barrierless excited state deactivation path that leads to a conical intersection displaying an orthogonal out-of-plane distortion of the terminal pyrimidine ring. The intersection structure readily explains the observed spectroscopic behavior in terms of an excited-state barrier imposed by the rigid glass cavity.

Original languageAmerican English
Pages (from-to)9870-9875
Number of pages6
JournalAngewandte Chemie - International Edition
Issue number37
StatePublished - 8 Sep 2014
Externally publishedYes


  • conical intersection
  • flavins
  • fluorescence probe
  • internal conversion
  • luciferase


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