Tunnel radius plots for SMO. (A) Free-energy plot of the tunnel diameter along the z coordinate for SANT1-bound SMO. (C) same as (A), but for Apo-SMO. (E) Same as (A), but for SAG-bound SMO. SAG-bound SMO clearly shows the expansion of the tunnel compared with Apo-SMO and SANT1-SMO. (B) SANT-1 SMO, (D) Apo-SMO, and (F) SAG-SMO shown with a representative tunnel. Tunnel radii were calculated using the HOLE program (95). To see this figure in color, go online.