FIGURE 2.

Dimensions of Shaker channel intracellular blockers. (A) Plots of MC-minimized energy of correolide pulled via the variable-diameter rings of methane molecules. The zero position corresponds to the epoxy group of correolide in the plane of the ring. The energy barrier increases sharply as the diameter decreases from 10 to 9.5 Å. (B) The superposition of MC-minimized structures of correolide pulled through the rings with inner diameter d_i of 8 and 10 Å. Large deformations of correolide in the smaller ring explain the high energy barrier shown in A. MCM caused some methane molecules of the smaller ring to violate in-plane constraints to avoid strong repulsions with their neighbors. (C) Plots of MC-minimized energy of tetrabutylammonium pulled via the variable-diameter rings of methane molecules. The zero position corresponds to the nitrogen atom in the plane of the ring. The barrier increases sharply as the diameter decreases from 6.5 to 6 Å. (D) The superposition of MC-minimized structures of tetrabutylammonium pulled through the rings inner diameter d_i of 6 and 8 Å.