Given the success with CHARMM36m, we also investigated charge-scaling with Amber14SB and Amber14SB-1.3σ. Amber presents difficulties because unlike CHARMM the side chain does not carry a full integer charge and cannot be simply scaled. Instead we linearly interpolate between the protonated and deprotonated cysteine to get a charge-scaled residue. Charge scaling Amber14SB improved prediction accuracy on the DsbA test set but failed to meaningfully saturate on the interval [1.00, 0.60], while charge-scaling Amber14sb-1.3σ improved prediction accuracy which was maximized for 0.80 and appeared to degrade for further scaling (Figure ). Probing Amber14sb-1.3σ with 0.80 charge scaling on the entire dataset improved the accuracy from an AUE of 2.88 ± 0.38 pK to 2.45 ± 0.27 pK; this improvement was smaller than that observed for CHARMM36m. Accounting for coupling also pushed the accuracy slightly higher to 2.37±0.29 pK.