Our decisions regarding the fitting of torsion energy profiles warrant some discussion and comparison to published studies. Previously published force fields have either employed QM torsion scans similar to this work, or used custom MM simulations to generate input conformations for QM calculations. During the development of a nucleic acid force field, QM and MM minimizations were carried out prior to comparing energies in a similar procedure to this work. The weighting scheme we used is comparable with a previous study that employed a Boltzmann distribution with = 2000 K ( ≈ 4.0 kcal/mol) to assign weights in fitting torsion energy profiles.