Figure 1.

Opening and closing of the gate to the active site of AChE. The five aromatic residues serving as the gate are shown such that the viewer is looking down the active-site gorge and into the active site. The surface accessible to a 1.4-Å probe is shown as dots. (Upper) Configuration at 12 ps along a 750-ps MD trajectory. The gate is closed to the 1.4-Å probe (but is open to a 1.2-Å probe). (Lower) Configuration at 68 ps along the MD trajectory. The gate is open even to a 2.6-Å probe (but is closed for a 2.8-Å probe).