The Jvert
(J-modulated spin echo; also known as SEFT – Spin Echo Fourier
Transform) experiment is the simplest method of encoding the
multiplicity of carbon signals on to the phase (i.e. .CH and CH3 up, C
and CH2 down) of a fully decoupled 13C spectrum. It
is simpler and easier than DEPT to set up because it doesn’t depend on
accurate calibration of decoupler pulses for good quality spectra. This method does not use polarization transfer
to create 13C signals but relies only on the nOe enhancement from the
1H decoupling. The quatrinary carbons,
don’t benefit from any nOe enhancement (since there are no protons
attached), but are directly detected.
1. Collect
an optimized 13C spectrum using a full 90° pulse on
carbon and a d1 value of ~5-10 sec. to allow for complete relaxation.
2. Type
gain='y'
gain? --note the value of the gain
3. Type
jvert
to set up the Jvert experiment.
4. If
necessary, adjust the following parameters:
· pw -
full 90° pulse for 13C listed at console (should be the
same as used above)
· p1 - do not set, it is automatically calibrated
from the pw setting
· tpwr -
transmitter power listed at console (also the same as above)
· j -
average 1H-13C coupling constant (about 140 Hz)
· d1 -
relaxation delay, approximately 3*T1 - at (also the same as
above)
· nt -
multiple of 8, best if multiple of 16
· dm - should be ‘yny’
5. Type
ga
to start the experiment.
6. Type
wft
and phase the spectrum, CH, CH3 up and C, CH2 down.