For example, residues 8-21 have a large deviation from the experimental structure and this is reflected by high J coupling errors in this region. The backbone J coupling error, using the 2007 Karplus parameters, for residues 8-21 is 2.00 Hz which is almost double the total backbone error. This region corresponds to a β-sheet, which separates over the second half of the MD trajectory and contributes to the increased backbone RMSD. Aside from this region, the only other residues which show noticeable deviation from the crystal structure are Val39, Asp40, Gly41 and Thr55. However, the small deviations that are present in these four residues are also observed in simulations using the AMBER ff15ipq force field. Deviations between the simulated ubiquitin dynamics and experiment tend to be confined to regions without clear secondary structures. Often this is of little concern since both experimental NMR measurements and simulations with the AMBER force field also indicate flexibility in these regions (e.g. residues 7-11 and 72-74). However, deviations from the crystal structure in the disordered region between residues 54-66 is more of a concern, and contributes to the high J coupling and rising RMSD of the protein backbone over the second half of the simulation.