The 3D HNCG experiment allows the measurement of J(N-CG) coupling constants in ¹³C,¹⁵N-labeled proteins using the quantitative J-correlation approach.

Implementation on AVANCE spectrometers equipped with a third channel and pulsed field gradients (PFGs).

Two closely related schemes have been described:

Using water flip-back and WATERGATE ( 97JB409 )

Using PEP ( 97JB323 ).

The 3D HNCG experiment affords a 3D map with (F1,F2,F3=N,CO,NH) in which coupling constants are extracted from intensity ratio of the corresponding cross-peak and external diagonal reference peak.