Reference:
J. Pauli, M. Baldus, B.-J. van Rossum, H. de Groot and H. Oschkinat (2001) Chem. Biochem. 2 272-281. (Link to Article)

Minimum labelling: ¹⁵N, ¹³C

Dimensions: 3

Magnetisation is transferred from ¹H to ¹⁵N via cross polarisation and then selectively to the ¹³Cα using specific cross polarisation. A DREAM step is then used to transfer magnetisation to ¹³Cβ nuclei further along the amino acid side chain. The chemical shift is evolved on the ¹⁵N and ¹³Cα nuclei and then detected on ¹³C, resulting in a 3D spectrum. A 2D version in which the ¹³Cα evolution time is left out is also possible.

This spectrum is very useful for identifying amino acid spin systems and to some extent ‘decrowding’ the NCACX spectrum. The DREAM transfer is optimised for transfer from Cα to Cβ, but some Cγ will also become excited and be visible in the spectrum, because their chemical shifts are similar to some Cβ chemical shifts. Because the DREAM transfer is a double quantum step, the Cβ peaks will be negative and the Cγ peaks will be positive.