(a) Two different dielectric boundaries. The vdW protocol defines the gray shaded region as the solute dielectric; the SE protocol adds the crevices, shaded in green, not accessible to a spherical solvent probe to the solute dielectric. (b) Smoothed vdW dielectric boundary. From left to right, the first, third, and fourth vertical dashed lines indicate the start, midpoint, and end of the dielectric transition region; the second vertical dashed line indicates the location of the original atomic surface.