RMS deviation (in units of inverse Å) between inverse effective radii, computed by the GBn and OBC GB models relative to the PB reference with significance of improvement measured by F-test. The β-hairpin and thioredoxin structures are in their native states, while apomyoglobin is represented by two partially unfolded states along an acid denaturation trajectory.46 Both models perform more poorly on thioredoxin than other structures due to a higher number of large effective radius atoms in thioredoxin. The much larger p-value for β-hairpin is due to the small number of atoms in the molecule, resulting in fewer degrees of freedom in the F-test.