Figure 3.

Free energy profile (PMF) for the zinc-bound water deprotonation reaction when His64 is not included as a proton acceptor in the MS-EVB model. The PMF is plotted as a function of the radial distance of the CEC to the catalytic zinc, R_Zn–CEC. The thickness of the line denotes the standard deviation, which was evaluated to be 0.4 kcal/mol. Also shown is the largest EVB state population ${\text{c}}_{max}^2$ (colored contours) as a function of the center of excess charge coordinate R_Zn-CEC. Red indicates high probability while blue indicates low probability. A Zundel cation has a ${\text{c}}_{max}^2\approx 0.5$, whereas the Eigen cation has a ${\text{c}}_{max}^2\approx 0.65$.