The 2D H(N)CO experiment is basically a modified 3D HNCO experiment in which the variable ¹⁵N evolution period has been fixed.

Implementation on any AVANCE spectrometer equipped with an inverse probehead, a third channel and pulsed field gradients (PFGs). The experiment is better applied on ¹⁵N,¹³C-labeled proteins. Because the amide (NH) protons are involved, the HNCO experiment must be recorded in H₂O. For this reason, a small isotope shift about 0.08ppm must be taken in account when comparison of absolute carbonyl chemical shifts are made in D₂O and H₂O. .

The original sequence was reported ( 95JB411 and 96JMRB305-111 ) for backbone 13CO resonance assignment purposes in small and medium-size ¹⁵N-labeled proteins. Recently, the experiment has been used for the measurement of very small coupling constants through hydrogen-bond networks ( 99JACS1601 , 99JACS2949 , 00JB279 ).

Related experiments:

The sensitivity of the HNCO-type experiments can be enhanced by quenching scalar coupling mediated relaxation. This is performed by applying CPD on alpha carbons, when a long 15N-13CO defocusing/refocusing period is required. This can be highly useful to detect weak, through hydrogen-bonds HN-CO dipolar couplings without resorting to perdeuteration. ( 00JB55-17 , 00JB79-17 )

A related 3D CO-edited NOESY-H(N)CO experiment has been proposed for resolving NOEs from degenerate HN that are attached to degenerate 15N resonances in ¹³C,¹⁵N-labeled proteins ( 96JMRB305-111 ).

Similar 2D H[NCO] and 2D H[NCA] experiments were proposed ( 94JB325 ) in which both ¹⁵N and ¹³CO (¹³CA) chemical shifts are displayed in the F1 dimension

A 2D H(N)C_aro experiment has been proposed to correlate NH protons with aromatic carbons in tryptophan and histidine sidechain residues ( 02JB153-22 ).

The 2D H(N)CO experiment affords an heteronuclear 2D NH (F2 dimension)/ ¹³CO (F1 dimension) correlation map.

Related experiments:

Multidimensional NMR experiments for proteins