From a structural perspective, it can be seen from Table that our EVB calculated transition states are very similar for the wild-type and all twenty simulated FuncLib variants, in terms of D-A distance and D-H…A angle. In addition, the electrostatic contributions of different residues are also relatively similar (Figure , which is unsurprising in light of the fact that, as discussed elsewhere, the change in charge distribution between Michaelis complex and transition state is very small, making it hard to obtain any significant gains from electrostatic stabilization in this reaction. Where there are larger differences are in the structures of the reacting atoms at the Michaelis complex, where the D-A distance ranges from 2.64 -4.25Å, and the D-H…A angle ranges from 129.8 -167.1°, with significant correlation between the calculated activation free energy and the D-H distance and D-H…A angle (Figure and). That is, R 2 = 0.84, and -0.81 for the correlation between the calculated activation free energy and the D-H…A angle when taking into account only the wild-type enzyme and the FuncLib variants, and 0.82 and -0.78 for distances and angles, respectively, when including also the single residue substitutions considered in Table . ).