Magnetization transfer between two J-coupled heteronuclei, I and S, is usually achieved by a pair of simultaneous 90° pulses in the so-called Hetero-COSY block, preceded and followed by delays for J dephasing and rephasing. A simple way to remove unwanted magnetization is obtained applying a PFG between these two pulses in order to select the desired zz magnetization.

This building block is largely used in gradient-enhanced multidimensional HSQC-type experiments.

Easy implementation on AVANCE spectrometers equipped with gradient technology.

The standard way to implement an heteronuclear magnetization transfer element in a pulse program is:

... (p1 ph2):f1 d13 p16:gp1 d16 (p21 ph3):f3 ...

in which:

• p1 is the high-power 90 pulse from the f1 transmitter channel (usually 1H) and p21 is the high-power 90 pulse from the f3 decoupler channel (usually or 15N)
• p16 is the duration of the gradient (in microseconds)
• d16 is the recovery time (in seconds) needed after the gradient
• gp1 stands for the gradient strength defined in the gpz1 command. Otherwhise, gpnam1 defines the shape of the gradient.

The heteronuclear magnetization transfer element is usually combined with water suppression purposes using the water flip-back technique in HSQC-type experiments