These are instructions for measuring 1D NOE spectra on the Bruker 400 using Xwin-NMR 3.5 in two different ways: using a selective inversion pulse on the peak of interest and using selective irradiation on the lines of a multiplet of interest followed by subtraction of a "blank" spectrum (one where the irradiation is far from any peak).

These two techniques have different strengths and weaknesses. The selective pulse technique is easier to set up and gives a much better background (peaks that are not involved in any NOE interaction are wiped out). The multiplet irradiation technique works well at controlling intensity distortions (a.k.a. selective population transfer or SPT) between signals that are J-coupled, and the percentage of enhancement is readily measured. The SPT may mask small NOE effects. The disadvantage of this (or any other) difference technique is that spectral subtraction is never perfect and there will always be some residual signal from peaks that do not have an NOE. The subtraction error is generally dispersive--it has both positive and negative components and would integrate to near zero. Real NOE effects should be purely in phase and have a nonzero integral.

NOE's can also be observed in 2D by NOESY or ROESY experiments. If the solution is concentrated, a NOESY experiment can be done in as little as 16 minutes.

Caveats about all NOE experiments

Setup of selective NOE:

Setup of NOE difference (noemult):