MPID polarizable force field: GPU implementation and biomolecular simulations.

The multipole and induced dipole (MPID) model provides a sophisticated description of electrostatics through permanent atomic multipoles up to the octupole level and point induced dipoles, but its high computational cost has limited its routine application to biomolecular simulations. Here, we present a GPU-accelerated implementation of the MPID model in OpenMM. The implementation produces energies and forces fully consistent with those obtained from CHARMM and enables routine microsecond-scale molecular dynamics simulations of explicitly solvated protein systems. Moreover, force field parameters were transferred directly from the Drude oscillator model to the MPID framework without reparameterization, yielding the MPID-2019 protein force field. Tests on five proteins show that MPID-2019 reproduces a range of NMR observables, including scalar couplings and relaxation order parameters. These results demonstrate that MPID-2019 is a valid polarizable force field that is readily applicable to protein simulations and that the effective equivalence of the induced dipole and Drude oscillator formalisms can be established at the biomolecular level.