Bioluminescence is greatly affected by proton migrations both directly on the chromophore and indirectly on protein side-chains. In this presentation, we discuss the pH dependent changes in the firefly bioluminescence based on molecular dynamics simulations and quantum chemical calculations. We find that the firefly luciferase structure fluctuates only mildly in a wide range of pH conditions. In contrast, we observe that the electrostatic tuning by the protonation state change has more drastic effects on the luminescence. In addition, we show that a water molecule in the active pocket helps its neighboring residues to have flexible motions inside the pocket. This flexibility also modulates the emission properties to a substantial degree. With these, we suggest that the active pocket will be in a dry condition during the luminescence process. These results represent the importance of understanding the dynamic aspects near the active pocket for elucidating the detailed photochemistry of bioluminescence.

Proton-transfer-induced modification on firefly bioluminescence

248th National Meeting (2014)

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