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. Author manuscript; available in PMC: 2019 Jul 18.
Published in final edited form as: J Am Chem Soc. 2018 Jul 9;140(28):8965–8969. doi: 10.1021/jacs.8b05177

Figure 3.

Figure 3.

Two-dimensional free energy surface as a function of the proton transfer coordinate (R1 – R2) and the P–O bond breaking/forming coordinate (R3 – R4) for the Pol η system with (A) two metal ions and (B) three metal ions in the active site. For each system, the MFEP is shown in black, with the images along the string depicted as black circles, and the free energy along the MFEP is shown in the inset as a function of evenly spaced images. The two-metal system follows a sequential mechanism, with phosphoryl transfer preceding proton transfer, while the three-metal system exhibits only phosphoryl transfer with no subsequent proton transfer. The results from two independent string simulations corresponding to two different initial mechanisms, along with statistical error bars, are given in Figures S2 and S3 for the systems with two metal ions and three metal ions, respectively.