Development of force field parameters for oxyluciferin on its electronic ground and excited states

Abstract

Construction of force field parameters of the oxyluciferin molecule on its electronic ground and excited states is presented. Several new approaches are introduced for more reliable parameterization: argon-scanning, Hessian matching, and constrained-group parameterization. The Ar-scanning approach is for fitting Lennard-Jones parameters so that the constructed force field can mimic the changes in ab initio energy of oxyluciferin-argon pair at various argon positions. The Hessian matching procedure is to closely reproduce the second derivative matrix of the bonded interaction terms of the force field functions, in comparison with the quantum chemically obtained results. The constrained-group algorithm is applied for both of these approaches to enable an automated atom-type-based parameterization. For complete description of the force field of the oxyluciferin molecule, we have also adopted the second order perturbatively corrected one-particle density matrices to obtain the atomic partial charges within the conventional framework of the restrained electrostatic potential fit. With the availability of the full force field parameter sets, the differences in condensed-phase dynamics on the two states can be investigated. As a simple demonstration, molecular dynamics simulations of aqueous oxyluciferin solution have been performed. The surrounding water structures for the two cases are analyzed by inspecting both the static solvent distribution functions as well as time variation of solvent-solute interaction. The contributions of charge-charge and dispersive interactions toward the solvation dynamics are also discussed.

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