The ge-2D inverse HOESY experiment is the inverse-detected gradient-enhanced version of the HOESY experiment. It is designed to detect and measure long-distance NOEs between different heteronuclei. Spectra showing better sensitivity and quality are obtained when compared with X-detected analogs.

Easy implementation on any AVANCE spectrometer equipped with pulsed field gradients (PFGs) and inverse probehead.

The basic pulse sequence of the inverse HOESY experiment is proposed in 96MRC532 . The pulse sequence is very similar to the X-detected HOESY experiment but channels are exchanged. The sequence starts with a 90º pulse on the low-abundant nucleus (X) which evolves during the variable t1 period under the chemical shift effect. A defocusing gradient is inserted in this period. A second 90º X pulse creates longitudinal z-magnetization and NOE transfer during occurd during the mixing time. A final 90º pulse on the abundant nucleus (I) creates tranverse magnetization and a refocusing gradient is inserted prior to acquisition  to refocus only the desired signal. Detection of the abundant nucleus is performed under X-decoupling. In the original publication, magnitude mode spectra were obtained. Alternatively, echo-antiecho approach could be applied in this same sequence by inverting the refocusing gradient on alternate scans and by storing the data separately. The applicability of the method has been demonstrated for ge-2D ³¹P-¹H and ⁷Li-¹H inverse HOESY experiments. Recently, a modified sequence has been proposed for reduction of t1 spectral artifacts 02MRC361 .

A modified ¹³C-based sequence has been propose incorporating an X-filter to remove ABX strong coupling signals ( 99JMR89-138 ).

The ge-2D inverse HOESY experiment can be recorded in routine/automation modes and minor changes are required if a predefined parameter set is available. Although in theory a single scan per t1 increment should be necessary, in practice a minimum 8 scans per t1 increment is required for good suppression of axial peaks. However, this is not a serious drawback because inverse HOESY is quite insensitive and usually a large number of scans must be recorded. As in any NOESY-type experiment, the most important parameter to optimize is the mixing time.

Tutorials: 2D inverse experiments

Tutorials: 2D gradient-based inverse experiments

The inverse HOESY experiment yields a 2D heteronuclear correlation spectra with minimal t1-noise, consisting only of genuine heteronuclear NOE cross-peaks

Related experiments:

2D Inverse experiments

2D Inverse gradient-enhanced experiments