The 2D spin-echo difference CT-HSQC experiment allows to measure coupling constants in labeled proteins. Basically is a CT-HSQC pulse sequence which can be slightly modified to measure specific coupling values.

Implementation on any AVANCE spectrometer equipped with an inverse probehead.

In the so-called spin-echo difference methodology two spectra are acquired:

A reference 2D CT-HSQC spectrum with the coupling of interest refocussed during the indirect evolution period

An attenuated 2D CT-HSQC spectrum with the coupling of interest active during the indirect evolutnio period

The ratio of the integrated intensities in the reference and the difference (reference minus attenuated) spectra can be related to the magnitudes of the couplings.

Several applications have been reported:

2D ¹³C-{¹⁵N} spin-echo difference CT-HSQC experiment to measure J(C-N) coupling constants ( 92JMR428 , 93JACS5334 and 94METH79 ). Useful to measure J(N-CG) in Thr and Val residues.

2D ¹³C-{¹³CO} spin-echo difference CT-HSQC experiment to measure J(C-CO) coupling constants. Useful to measure J(CO-CG) in Thr and Val residues ( 93JB487 )

2D ¹³C-{¹³CA} spin-echo difference CT-HSQC experiment to measure J(CD-CA) coupling constants ( 96JB256 )

2D ¹³CO-{¹³CG} spin-echo difference ¹H-¹⁵N HSQC experiments to measure J(CO-CG) coupling constants in aromatic systems ( 97JACS1803 and 97JB323 ).

2D ¹⁵N-{¹³CG} spin-echo difference ¹H-¹⁵N HSQC experiments to measure J(N-CG) coupling constants in aromatic and aliphatic systems ( 97JACS1803 and 97JB323 ).

Measurement of one-bond ¹HA-¹³CA dipolar couplings in ¹³C,¹⁵N-labeled proteins ( 97JMR512-124 )

The 2D CT-HSQC experiment can be recorded in routine/automation modes. Minor changes are required if a predefined parameter set is available.