The 3D NOESY-HMQC experiment is specifically designed to obtain X-edited NOESY spectra of X-labeled biomolecules protein-ligand complexes from which homonuclear ¹H-¹H NOEs can be clearly assigned even in overcrowded regions (the mechanism involves ¹H-¹H NOE step followed by an heteronuclear transfer via ¹J(XH)). Similar results can be obtained from an analog 3D NOESY-HSQC experiment.
          

Implementation on AVANCE spectrometers is feasible. Improved versions using pulsed field gradients (PFGs) are also available and, therefore, in such cases gradient technology is required. The ¹H-¹³C NOESY-HMQC experiment is usually applied on ¹³C-labeled proteins in D₂0 and the ¹H-¹⁵N NOESY-HMQC is usually applied on ¹⁵N-labeled molecules in H₂0.

The original 3D NOESY-HMQC pulse sequence ( 88JMR588-78 , 89BIO6150 , 89BIO2387 , 89JACS1515 , 89JMR608-85 , 89JMR72-84 , 92JMR192-99 , and 90JMR204-86 ) basically consists of an homonuclear 2D NOESY pulse sequence followed by a 2D ¹H-X HMQC pulse sequence.

Several improved versions have been proposed incorporating the following modifications:

• Sensitivity improvements by incorporating the PEP methodology  ( 92JMR416-96 ).
• Use of PFGs ( 92JB301 ) and PFG with water flipback ( 98JMR87-135 ).
• Improved sensitivity using the multiple-quantum narrowing approach ( 99JB133-14 ).
• Improved sensitivity using a 45 degree water flip back pulse ( 99JMR451-140 ).
• Measurement of 3J(CB,NH) coupling constants ( 94JMRB172-104 ).
• Closely related 3D ROESY-HMQC pulse schemes have been also proposed ( 90BIO5671 , 95JB335 , and 99JMR451-140 ).
• 3D HMQC-NOESY-HMQC experiments can also be used to observe NOEs between  protons with degenerate chemical shifts.

The 3D NOESY-HMQC experiment can be recorded in automation mode.

More details on practical implementation of the 3D NOESY-HMQC  experiment on AVANCE spectrometers can be found in the corresponding Tutorial 3D NOESY-HMQC experiment

The NOESY-HMQC  experiment affords a 3D spectrum in which ¹H, X and ¹H chemical shifts are displayed in three independent dimensions. Thus, the F₁(¹H)-F₃(¹H) plane of a ¹H-¹⁵N NOESY-HMQC spectrum will show a typical 2D F₁(¹H)-F₂(NH) NOESY map. On the other hand, the F₁(¹H)-F₃(¹H) plane of a ¹H-¹³C NOESY-HMQC spectrum will show a typical 2D F₁(¹H)-F₂(¹H aliphatic) NOESY map while the F₁(¹H)-F₂(¹³C) plane will correspond to a conventional 2D ¹H-¹³C HSQC spectrum.

General Reading: ( 96ENC4733 )