Figure 2
On top, schematic view of the open and closed states of the HE7 gate. On the bottom, free energy profiles for O2 migration from the solvent to the distal site in the closed state (left), with HE7 in the HIE protonation state, and in the open state (right), with HE7 in the HID protonation state. For the sake of simplicity, error bars were included only at the Free Energy barriers. In all cases, error estimation resulted lower than 2.1 kcal/mol along the whole free energy profile.
