To check the validity of the proposed force field modifications, we computed the potential energy profiles for the N-C α -C β -C γ dihedral of aspartic acid with capped residues. The profiles were computed at both quantum mechanical (QM) and molecular mechanical (MM) levels. The QM profiles were computed at the MP2/6-31+G* level of theory using Firefly QC package, which is partially based on the GAMESS (US) source code. The MM profiles were computed for both the original and modified CHARMM36m force fields. The potential energy was computed for N-C α -C β -C γ dihedral angle with 10 • increments. For each dihedral value, the structures were energy-minimized prior to potential energy calculation.