L.E. Kay, M. Ikura, R. Tschudin and A. Bax (1990) J. Magn. Reson. 89 496-514. (Link to Article)
S. Grzesiek and A. Bax (1992) J. Magn. Reson. 96 432-440. (Link to Article)
D.R. Muhandiram and L.E. Kay (1994) J. Magn. Reson., Ser. B 103 203-216. (Link to Article)

Minimum labelling: 15N, 13C

Dimensions: 3

Magnetisation is passed from 1H to 15N and then selectively to the carbonyl 13C via the 15NH13CO J-coupling. Magnetisation is then passed back via 15N to 1H for detection. The chemical shift is evolved on all three nuclei resulting in a three-dimensional spectrum.

HNCO magnetisation transfer

This is the most sensitive triple-resonance experiment. In addition to the backbone CO-N-HN correlations, Asn and Gln side-chain correlations are also visible.
It is mainly used to obtain CO chemical shifts which can be used in a program like TALOS to help predict secondary structure.
The HNCO can also be useful for backbone assignment in conjunction with the HN(CA)CO, if the CBCANNH and CBCA(CO)NNH spectra are of bad quality.

HNCO spectrum