Heteronuclear Cross-Polarization (HCP) (also known as Hetero-TOCSY, HSL (Heteronuclear Spin-Locking) or HEHAHA (HEteronuclear Hartmann-Hahn)) is an alternative way to INEPT-like or DEPT-like transfer to transfer polarization between two different nuclei. It can be viewed as the heteronuclear version of the TOCSY or HOHAHA experiment.

Good heteronuclear polarization transfer can be achieved using isotropic mixing sequences as MLEV, WALTZ-16 ( 89CPL432 and 90JMR533-89 ) , DIPSI-2 and DIPSI-3, and the efficiency of these schemes have been analyzed in detail ( 91MP219 , 91JMR413-91 and 00JMR369-142 ). New broadband heteronuclear Hartmann-Hahn sequences have been designed ( 94JMRA115-111 and 97JMR110-126 ). A quality factor describing the relative sizes of cycle time, bandwidth and maximum RF amplitude for any given multiple-pulse sequence can be defined ( 00JMR369-142 )

Applications:

13C-detected 1D HCP experiment.

13C-detected 2D HCP experiment.

Long-range connectivites can also be traced out using a longer mixing time ( 89CPL432 , 91MRC83 , 92MRC662 , 92JMR139-100 , and 92JACS10651 ).

Analogs proton-detected experiments have also been reported:

Multidimensional experiments for proteins

HCP applied on 31P for nucleic acids ( 92JMR176-98 and 93JB577 )..

Applied to 113Cd

The HCP procedure is largely applied in multidimensional NMR experiments of labeled biomolecules instead of the conventional INEPT-like transfers.

Easy implementation on AVANCE spectrometers. Accurate power level and pulse width optimizations in proton and X-channels are required.