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

Implementation on AVANCE spectrometers is feasible. Improved versions using pulsed field gradients (PFGs) are also available and, therefore, gradient technology is required. The ¹H-¹³C HSQC-NOESY experiment is usually applied on ¹³C-labeled proteins in D₂0 and at natural abundance on concentrated samples. On the other hand, the ¹H-¹⁵N HSQC-NOESY is usually applied on ¹⁵N-labeled molecules in H₂O.

The original 3D HSQC-NOESY pulse sequence ( 88JMR588-78 ) basically consists of a 2D ¹H-X HSQC pulse sequence followed by an homonuclear 2D NOESY pulse sequence. Related experiments are:

• The starting HSQC block could be replaced with other heteronuclear schemes:
  decoupled HSQC, CT-HSQC, HSMQC ( 90JMR210-86 , 90JACS5370 , and 94JMRB193-104 )
  HMQC ...(see, for instance, the 3D HMQC-NOESY experiment).
  TROSY ( 00JMR195-142 ) (3D TROSY-NOESY experiment).
• The NOESY block can be replaced by a COSY, ROESY or a TOCSY block (see, for instance, the 3D HSQC-TOCSY experiment).
• The two building blocks can be reversed (see 3D NOESY-HSQC experiment)
• A 2D version can be designed by fixing the variable ¹³C evolution period in the HSQC block (2D w1-X-filtered NOESY experiment) or by fixing the variable ¹H evolution period (see 2D HSQC-NOESY experiment). In addition, a ¹³C-selective 1D HSQC-NOESY could be obtained by fixing both variable evolution delays.
• A w2-filtered version has been proposed that uses an X-filter element prior to acquisition ( 96JB492-8 ).

Several improved versions have been proposed incorporating the following modifications:

• Several 2D and 3D TROSY-based schemes with diagonal peak suppression
• Use of PFGs ( 93JMRB242-102 ).
• 1H-15N HSQC-NOESY sequence using WATERGATE for 13C,15N-labeled proteins in water ( 01JB261-19)
• 3D 1H-13C-TROSY-NOESY experiment for 13C-labeled RNA molecules ( 98JACS11845 and 01JB141-19)

The 3D HSQC-NOESY experiment can be recorded in automation mode. Both blocks are usually optimized as in their 2D counterparts.

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

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