FIGURE 7.

Electronic energies and approximate Gibbs free energies for states A through F in Fig. 6 (energies are relative to state B). State Z is shown as a reference and corresponds to a positively charged histidine and a water molecule (Z). Figure key: vacuum optimized coordinates energy (□) and Gibbs free energy (○); water optimized coordinates, energy (Δ); and Gibbs free energy (▿). Single point energies calculated with B3LYP/6-311++g(2d,p) using the coordinates optimized in implicit water without the diffuse functions (◊). Energies of intermediate structures between the states in Fig. 6 optimized in the gas phase (▪) are also shown.