The OPBE/6-31G(d,p)//PM6-D3H+ calculations reproduce the experimental chemical shifts to within 2.8 ppm for carbon atoms, 0.6 ppm for hydrogen atoms and 4.6 ppm for nitrogen. The results are similar to those observed by other researchers using other functionals. For example, Zhu and co-workers \cite{Zhu_2012} used B3LYP3/6-31G(d,p)//AMBER (and a locally dense 6-31++G(d,p)/4-31G(d) basis set for C’) and an implicit solvent model to reproduce chemical shift values to within 3.3 ppm for carbon atoms, 0.4 for hydrogen atoms and 8.4 ppm for nitrogen. In this study the RMSD for hydrogen atoms was computed for H\(\alpha\) and H\(^\text{N}\) combined. In a later study \cite{Zhu_2013}, the same researchers reproduced the chemical shifts of amide protons in GB3 to within 0.5 ppm using a locally dense 6-31++G(d,p)/4-31G(d) basis set and a variety of functionals including OPBE. Similarly, Exner and co-workers \cite{Exner_2012} used B3LYP/6-31G(d)//AMBER and an implicit solvent model to reproduce the H\(^\text{N}\) chemical shifts of the HA2 Domain to within 0.5 ppm using a single structure and 0.3 pm using several MD snapshots.