Sample: 100mM Urea ¹⁵N, 100mM CH₃OH ¹³C in DMSO-d₆

The calibration of the high-power 90º ¹⁵N pulse via the decoupler channel is performed using the same parameters as a conventional ¹H spectrum and defining NUC2 15N (the pulse program is decp90) in which a 90º ¹⁵N pulse length about 25-35 usec is required.   If you need to calibrate this pulse from the f3 channel. you must use the pulprog decp90f3:

Use the following values:

p1=high-power 90º ¹H observe pulse

d2=1/2*J_NH=5.649ms for 88.5 Hz.

ns=1

It is very important to use a long recycle delay, usually d1=5*T1(¹H) (d1=20 s).

The urea resonance is monitored as a function of the pulse length.  From this resonance we define the phase correction (using the phase subroutine) and plot region (using the DefPlot button) to be monitored. o1 and o2 are set on-resonance of the selected ¹H and ¹⁵N (76 ppm) resonances, respectively.

Start acquisition with rga and zg using a value of p3=25-35us at a high power level pl2 . After proper phasing, the first spectrum shows an up-down doublet for the urea resonance near to 5.45 ppm. Repeat the experiment increasing the value of pl2 until a nul point for the doublet is achieved (this is the 90º ¹⁵N decoupler pulse). When pl2 reachs 180º degree, the doublet shown a reverse down-up pattern.

Use standard ¹H processing parameters (efp with lb=0.3).

For a three channel system calibrate also the 90 degree pulse for the third channel with decp90f3. Use all necessary filters.