The Drude polarizable force field is the polarizable version of the CHARMM family of force fields . It accounts for polarizability by attaching an auxiliary charged particle to each polarizable atomic center with a harmonic spring. A small charge and mass are transferred from the parent atoms to the Drude particles, allowing them to be treated as dynamical particles that move around their parent atoms. A key advantage of this approach is that the movements of the Drude particles can be accommodated in the usual MD scheme with little modification, rather than requiring the added code needed to handle the inducible dipole model above. However, the added particles make for a somewhat more complex system, a dual-thermostat extended Lagrangian algorithm is used to keep the Drude particles at a very low temperature (∼1K), and a 1-fs time step is employed because the Drude oscillators have high natural frequencies. Following introduction of the Drude polarizable water model 2003 , the Drude polarizable force field has successfully been extended to proteins, DNA, lipids, and carbohydrates. The fluctuating charge (FQ) model describes polarization by allowing charge to flow between atoms in response to the electric field, 37-39 so neither inducible dipoles nor added charge centers are required. The modified charges are typically obtained via an electronegativity equalization approach, whose solution can be somewhat time-consuming. Because charges can only flow along the direction of bonds, the FQ model does not describe outof-plane polarization. Nonetheless, the FQ representation can afford accuracy competitive with the induced polarizable representation. The present study builds on prior advances to propose two polarizable electrostatic models intended to afford a favorable balance of accuracy, ease of use, and computational speed.