Reference:
S. Grzesiek and A. Bax (1992) J. Magn. Reson. 99 201-207. (Link to Article)

Minimum labelling: ¹⁵N, ¹³C

Dimensions: 3

Magnetisation is transferred from ¹Hα and ¹Hβ to ¹³Cα and ¹³Cβ, respectively, and then from ¹³Cβ to ¹³Cα. From here it is transferred first to ¹⁵N^H and then to ¹H^N for detection. Transfer form Cα_i-1 can occur both to ¹⁵N_i-1 and ¹⁵N_i, or viewed the other way, magnetisation is transferred to ¹⁵N_i from both ¹³Cα_i and ¹³Cα_i-1. Thus for each NH group there are two Cα and Cβ peaks visible. The chemical shift is evolved simultaneously on ¹³Cα and ¹³Cβ, so these appear in one dimension. The chemical shifts evolved in the other two dimensions are ¹⁵N^H and ¹H^N.

Along with the CBCA(CO)NNH and HSQC this forms the standard set of experiments needed for backbone assignment. For large proteins the signal-to-noise may not be great and assignment using the HNCA, HN(CO)CA, HNCO and HN(CA)CO may form a better strategy. When using deuterated protein, the spectrum has to be recorded as an ‘out-and-back’ method and the signal-to-noise suffers even further.