The ge-2D INADEQUATE experiment allows to obtain a 2D INADEQUATE spectrum with a single scan per t₁ increment provided that the S/N ratio is adequate. The main advantage of such approach is the large reduction in the total acquisition time compared with a conventional 2D MQ experiment. The INADEQUATE experiment permits to trace out through-bond carbon-carbon connectivities via the homonuclear J_CC coupling constant.

Implementation on any AVANCE spectrometer equipped with pulsed field gradients and carbon-detected designed probehead is feasible. Inverse probehead will shown decreased sensitivity. High sample concentrations or 13C-labeled compounds are usually required.

The ge-2D INADEQUATE experiment is the ¹³C version of the ge-2D DQ experiment. It has been applied in studies of ¹³C-labeled compounds ( 94MRC665 ). PFGs can be included in the 2D INADEQUATE experiment for coherence selection after and before the mixing pulse, just prior to acquisition, by using a 1:2 gradient ratio but sensitive losses should be undesired. Alternatively, phase sensitive ge-2D INADEQUATE spectra can be obtained using the echo-antiecho approach ( 95JACS11365 ). An improved INADEQUATE-CR experiment doubles the sensitivity compared to the conventional experiments ( 96JCP3962 , 95JACS11365 , and 96JMRA135-123 ) . Off-resonance effects in such experiments can be minimized using compensated pulses ( 00MRC58 ).

For practical purposes, better sensitivity can be achieved using analog proton-detected derivatives. Non refocused and refocused ge-2D DQ experiments have also been applied in peptides and proteins ( 94JMRB83-105 ) and 13C-edited experiments has also been proposed for ¹³C-enriched proteins (3D HMQC-DQ experiment).

This experiment is acquired an processed using the same experimental conditions as described for its phase cycle version, depending if magnitude-mode or phase-sensitive spectrum is obtained. The only difference is the presence of the gradients. Thus, the user only need to define the strength, duration, shape of the gradients and the recovery delay. More details on practical implementation of ge-2D INADEQUATE experiments on AVANCE spectrometers can be found in

Tutorials: 2D X-detected experiments

In principle, the ge-2D INADEQUATE experiment can be recorded with minor required modifications if a predefined parameter set is available. Only gradient ratios and sample concentration play an important role.

In a 2D INADEQUATE spectrum, cross-peaks correlate 13C chemical shifts (F2 dimension) and double-frequencies (F1 dimension) between homonuclear 13C spins via homonuclear J(CC) coupling.

Related experiments:

2D X-detected experiments