References:
D. Marion, P.C. Driscoll, L.E. Kay, P.T. Wingfield, A. Bax, A.M. Gronenborn and G.M. Clore (1989) Biochemistry 28 6150-6156. (Link to Article)

Minimum labelleing: ¹⁵N

Dimensions: 3D

To start with, an isotropic mixing step transfers magnetisation between ¹H spins. Then the magnetisation is transferred to neighbouring ¹⁵N nuclei and back to ¹H for detection.

This can help identify amino acid types. If assignment is being done using ¹⁵N protein, only, it is a must. It can also help with the assignment of side-chain hydrogen atoms, though normally an HCCH-TOCSY or HCCH-COSY spectrum is necessary for unambiguous side-chain hydrogen assignment.