Whilst preparing the protein simulations, it was found that our library was missing parameters for the disulfide bridge between pairs of cysteine residues. These bond and angle parameters were therefore derived using the QM Hessian matrix of dimethyl disulfide and are supplied in Section S2.3 of the Supporting Information. With new bond, angle and non-bonded parameters derived, all that remains to complete the QUBE protein force field is to obtain the torsional parameters. Unfortunately, it is infeasible to derive torsional parameters from QM simulations that are specific to each protein.