The Effect of dynamical fluctuations of hydration structures on the absorption spectra of oxyluciferin anions in an aqueous solution

Hiyama, Miyabi*; Shiga, Motoyuki   ; Koga, Nobuaki*; Sugino, Osamu*; Akiyama, Hidefumi*; Noguchi, Yoshifumi*

In this study, the effect of hydration on the absorption spectra of oxyluciferin anion isomers in an aqueous solution is investigated for elucidating the influence of characteristic hydration structures. Using a canonical ensemble of hydration structures obtained from first-principles molecular dynamics simulations, the instantaneous absorption spectra of keto-, enol-, and enolate-type aqueous oxyluciferin anions at room temperature are computed from a collection of QM/MM calculations using an explicit solvent. It is demonstrated that the calculations reproduce experimental results concerning spectral shifts and broadening, for which traditional methods based on quantum chemistry and the Franck-Condon approximation fail because of the molecular vibrations of oxyluciferin anions and dynamical fluctuations of their hydration structures.