The effects of molecular surface definitions (sasopt) upon the performance of MMPBSA. Both the default Amber atomic radius definition (radiopt=0) and optimized atomic radius (radiopt=1) were used in the analysis. The testing conditions are otherwise the same as those in Table 1 but with all six tested combinations of surface and radius options. Here the solvent probe is set to the optimized value (dprob=0.6) in SES and DEN as reported in our previous studies26, 30. For VDW dprob=0.0 by definition. The RMSD’s of ΔΔG are in kcal/mol.