\(\Delta \sigma^i_{H\alpha B}\) is the effect of hydrogen bonding to the H\(\alpha\) and amide O atoms of residue \(i\) on the chemical shielding of the backbone atoms and C\(\beta\) and has two contributions \[\label{eqn:sigmahab} \Delta \sigma^i_{H\alpha B}=\Delta\sigma^i_{1^\circ H\alpha B}(r_{\mathrm{H\alpha O}},\theta,\rho)+\Delta\sigma^i_{2^\circ H\alpha B}(r_{\mathrm{OH\alpha}},\theta_{\mathrm{O}},\rho_{\mathrm{O}})\] \(\Delta\sigma^i_{1^\circ H \alpha B}\) is computed using the structural models shown in Figure \ref{fig:HAB} as the change in chemical shielding of the backbone and C\(\beta\) atoms in Ac-A-NMe relative to that of the free monomer computed at the OPBE/6-31G(d,p)//PM6 level of theory for a variety of orientations (see subsection \ref{subsec:HBscan} for more information) while the internal monomer geometries are kept fixed. \(\Delta\sigma^i_{2^\circ HB}\) is computed as the change in the chemical shielding of the top amide group in Figure \ref{fig:HAB}a. For H\(\alpha\) the chemical shielding is taken as the average of the three hydrogen atom on the methyl group of the acetamide. Note in this case that the amide nitrogen and hydrogen formally belong to residue \(i+1\) and that \(r_\mathrm{HO}\), \(\theta\), and \(\rho\) are defined relative to the carbonyl oxygen of residue \(i\) rather than the amide proton as for \(\Delta\sigma^i_{1^\circ HB}\). \(r_\mathrm{H\alpha O}\), \(\theta\), and \(\rho\) are therefore labeled \(r_\mathrm{OH\alpha}\), \(\theta_{\mathrm{O}}\), and \(\rho_{\mathrm{O}}\) in Eq \ref{eqn:sigmahab}.