The 2D HSQC-COSY experiment is an hybrid inverse experiment consisting of an initial HSQC pulse train and one or several RELAY building blocks. In the first step, magnetization is transferred from the X nucleus (13C or 15N) to the directly-bonded proton nuclei via ¹J(CH). In the second step, such magnetization is step-wise propagated through the whole coupled homonuclear spin network via J(HH). Similar results are obtained from the analog 2D HMQC-COSY experiment.

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

The basic sequence of the 2D HSQC-COSY experiment is based on the 2D HSQC experiment in which a 90º proton pulse is inserted prior to acquisition.

Improved results can be obtained from the gradient enhanced version (ge-2D HSQC-COSY experiment.

The 2D HSQC-COSY experiment can be recorded in routine/automation modes. The experiment is basically optimized as described for the 2D HSQC experiment.

More details on practical implementation of 2D HSQC-COSY experiments on AVANCE spectrometers can be found in

Tutorials: 2D inverse experiments

Tutorials: 2D gradient-based inverse experiments

The HSQC-COSY spectrum correlates chemical shifts of heteronucleus X (F1 dimension) and protons (F2 dimension) via the direct heteronuclear coupling ¹J(XH). Two different cross-peaks are present for each X resonance: The direct 1H-X connectivites (HSQC cross-peak) and the relayed 1H-X connectivity due to the cumulative transfer ¹J(XH)+J(HH). In the case of more relayed steps are included to the pulse sequence, magnetization is propagated to the whole proton spin network and, therefore, more relayed peaks will be detected. However, a 2D HSQC-TOCSY experiment can be preferred for this purpose.

Comparison of different 2D inverse correlations have been carried out ( 90JMR488-87 ).

Related experiments:

2D Inverse experiments

2D Inverse gradient-enhanced experiments