Theoretical fingerprinting of the photophysical properties of four firefly bioluminophores

The photophysical properties of four bare firefly bioluminophores were studied in vacuo by means of a density functional theory approach. The objective of this work was to fingerprint the excited-state properties of these molecules without perturbations of the microenvironment (either solution or enzyme active site). It is known that intermolecular interactions formed between the light-emitter and active site molecules govern the bioluminescence multicolor tuning mechanism. However, it is difficult to disentangle the numerous active site-oxyluciferin interactions and understand the effect exerted by each one of these interactions on the color of light emitted. Thus, the study of these isolated bioluminophores allows us to obtain their intrinsic photophysics properties, which can serve as a reference in studies aiming to understand the role of perturbations from the microenvironment.