Note:
The magnetization is passed from ${\phantom{A}}_{\phantom{}}^{\phantom{1}}{\phantom{A}}_{\phantom{2}}^{\phantom{2}1}\mathrm{H}$ to ${\phantom{A}}_{\phantom{}}^{\phantom{15}}{\phantom{A}}_{\phantom{2}}^{\phantom{2}15}\mathrm{N}$ and then to ${\phantom{A}}_{\phantom{}}^{\phantom{13}}{\phantom{A}}_{\phantom{2}}^{\phantom{2}13}\mathrm{CO}$. From here it is transferred to ${\phantom{A}}_{\phantom{}}^{\phantom{13}}{\phantom{A}}_{\phantom{2}}^{\phantom{2}13}\mathrm{C}\mathrm{\alpha }$ and the chemical shift is evolved. The magnetization is then transferred back via ${\phantom{A}}_{\phantom{}}^{\phantom{13}}{\phantom{A}}_{\phantom{2}}^{\phantom{2}13}\mathrm{CO}$ to ${\phantom{A}}_{\phantom{}}^{\phantom{15}}{\phantom{A}}_{\phantom{2}}^{\phantom{2}15}\mathrm{N}$ and ${\phantom{A}}_{\phantom{}}^{\phantom{1}}{\phantom{A}}_{\phantom{2}}^{\phantom{2}1}\mathrm{H}$ for detection. This is similar to the HNCA, but is selective for the $\mathrm{C}\mathrm{\alpha }$ of the preceding residue.