The starting structures were obtained by docking using OEDock (with the Chemgauss4 scoring function) from OpenEye Toolkits (release 2019.4.2). AM1-BCC partial atomic charges were generated with oequacpac function oequacpac.OEAssignCharges(mol, oequacpac.OEAM1BCCCharges()) as implemented with OpenEye Toolkits (release 2019.4.2). Each host-guest system was solvated with 2500 TIP3P water molecules in a rectangular box whose dimensions were approximately 40 x 40 x 63 cubic Å. Sodium and/or chloride counter ions (with parameters from Joung and Cheatham ) were added as needed to neutralize each host-guest system, and additional NaCl ions were added to obtain an ionic strength matching experimental conditions. To compare the performance of two general Force Fields (Parsley and GAFF2), the bonded and Lennard-Jones parameters for hosts and guests were assigned based on OpenFF v1.2.0 using the Open Force Field toolkit, or from GAFF2 as implemented in Antechamber .