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
The standard way to implement an heteronuclear magnetization transfer
element in a pulse program is:
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
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
with water suppression purposes using the
water flip-back technique in HSQC-type experiments