The 2D w₁-X-edited (filtered or selected) NOESY experiment affords a 2D NOESY spectrum in which ¹H directly-attached to X nuclei are efficiently filtered or selected before evolution during the variable t₁ period. This experiment is widely used to study protein-ligand complexes, where the protein is usually ¹³C and/or ¹⁵N-labeled and the ligand is at natural abundance .

Easy implementation on any AVANCE spectrometer equipped with an inverse probehead.

The basic sequence of the 2D w₁-X-edited NOESY experiment is easily designed by replacing the initial 90º ¹H pulse of a conventional 2D NOESY pulse scheme by an X half-filter ( 91ANG1329 ) or an X-filter element ( 96JB492-8 ). If required, a BIRD-recovery cluster can be used as a preparation period in order to reduce the large unwanted ¹H-X (typically, ¹²C or ¹⁴N) magnetization. Carbon decoupling is optionally applied during proton acquisition. Because there is no heteronuclear decoupling during t₁, all relay peaks appear as doublets in F₁ dimension due to ¹J(CH), reducing the sensitivity of the method.

Modified approaches have been reported using ¹³C/¹⁵N double half filters (w1-13C/15N-doubly edited NOESY experiments) and time-shared ¹³C-filters ( 00JMR168-144 )

Other closely related experiments are:

• w1-¹³C-filtered ROESY experiment to measure ⁿJ(CH) coupling constants ( 93JB81 ).
• 3D HMQC-NOESY experiment.
• 2D w₂-X-edited NOESY experiment.
• 2D w₁,w₂-X-edited NOESY experiment.

The 2D w₁-X-edited NOESY experiment can be recorded in routine/automation modes. The experiment is basically optimized as described for the 2D NOESY experiment. The X half-filter is optimized as described in a regular HMQC experiment and the phase cycle is selected in order to select or to filter the desired isotope.

Tutorials: 2D inverse experiments

Tutorials: 2D gradient-based inverse experiments

The 2D w₁-X-edited NOESY spectrum shows a typical 2D NOESY map in which cross-peaks show E.COSY pattern. The nJ(CH) values are measured from signal displacement in two F1 slices through each signal of the cross-peak doublet split by ¹J(CH) in the F1 dimension. Thus, coupling constants smaller than the linewidth can be determined accurately. In addition, the pulse sequence contains no delays to evolve ⁿJ(CH) as in HMBC-like experiments, which simultaneous allows evolution of J(HH). Therefore, the  spectrum is free from J(HH) modulation and it can be phased to pure absorption.

Analogs 3D NOESY-HMQC, 3D NOESY-HSQC, 3D HMQC-NOESY, and 3D HSQC-NOESY experiments can easily designed by incorporating a second variable evolution period in the HMQC/HSQC block as usual. On the other hand, a very similar pulse sequence is used for the 2D HMQC-NOESY and 2D HSQC-NOESY experiments by using a single variable evolution period in the HMQC/HSQC block .

Related experiments:

2D Inverse experiments

2D Inverse gradient-enhanced experiments