to better fit the dihedral potential energy surfaces; the atom types for each residue are listed in the Supporting Information. Additionally, we found a sizeable discrepancy for the phosphorous-oxygen (linking the amino acid side chain to the phosphate group) equilibrium bond length parameter for the dianionic phosphorylated amino acids compared to the value produced from the QM optimizations and of model phosphorylated analogues (detailed in the Supporting Information). As the parameter optimization is sensitive to the initial parameter values through the penalty function, we altered these initial bond length values in order to produce a more reasonable starting point for ForceBalance. GROMACS 5.1.4