Reference:
M. Baldus, A.T. Petkova, J. Herzfeld and R.G. Griffin (1998) Mol. Phys. 95 1197-1207. (Link to Article)

Minimum labelling: ¹⁵N, ¹³C

Dimensions: 2

Magnetisation is transferred from ¹H to ¹⁵N via cross polarisation and then selectively to the ¹³CO using specific cross polarisation. The chemical shift is evolved on the ¹⁵N nuclei and detected on the ¹³C nuclei.

This experiment can be used to obtain sequential links from N_i to CO_i-1 but for larger proteins, this is liable to be rather crowded and the 3D NCOCX experiment will probably be more useful.