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 for 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’) 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 Protein G 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.