pH‐Dependent Absorption Spectrum of Oxyluciferin Analogues in the Presence of Adenosine Monophosphate

International audience; The photophysical properties of oxyluciferin, the light emitter responsible for firefly bioluminescence, are pH-dependent. One of the potential proton accep-tor/donor is adenosine monophosphate (AMP). We have studied three oxylu-ciferin synthetic analogues with or without AMP, in water, in the pH=5 to 11 range, using both experimental steady-state absorption spectroscopy or the recently developed computational protocol that uses constant pH molecular dynamics and then hybrid QM/MM calculations (CpHMD-then-QM/MM). The latter features a systematic investigation of all the protonation microstates using molecular dynamics simulations coupled to thousands hybrid QM/MM vertical excitation energies. Our results demonstrate that AMP does not significantly modify the visible light absorption of the analogues, whatever the pH value. We also show that CpHMD-then-QM/MM is capable to qualitatively reproduce the pH-dependent absorption spectrum of the analogues, despite the employed low QM level of theory.