OLUFF: a novel set of ground and excited state force field parameters of the emitting oxyluciferin species.

The modeling of the bioluminescent system of fireflies is key to understand the binding mode of the oxyluciferin/luciferase complex and its photophysical properties with the aim of developing high-efficiency devices and techniques. In this work, we present the OLUFF force field, which is able to describe the interactions to sample the conformational space of the four possible oxyluciferin emitters in both ground and excited state. This force field has been parameterized to reproduce quantum mechanical (QM) energies and geometrical parameters. Moreover, it has been validated by comparing probability distribution functions, minimized structures, infrared spectra and normal mode analysis obtained from OLUFF-based molecular dynamic (MD) simulations with their QM counterparts. Additionally, ground state simulations have also been performed using the general amber force field (GAFF) and compared with the OLUFF. It has been demonstrated that the OLUFF not only reproduces well the QM properties, but also improves the results from the GAFF.