1D NOE Experiment

The 1D NOE experiment measures the distance-dependent nuclear Overhauser effect from one ¹H to protons within 5A.

Acquiring 1D NOE data

1. Acquire and process a 1-pulse experiment.

2. Place the cursor on the peak to be irradiated and type sd to set the decoupler frequency.

3. Adjust the following parameters:

ss=2

pw = ¹H 90° pulse width

d1 = 5*T₁, if T₁ is unknown, set to 7

nt = minimum of 16

dn=H1

dof = set by step 1

dm=yyn

dmm=c

dpwr=10

homo=y

lb = minimum of 0.5

dp=y

4. Acquire and process a spectrum.

5. Adjust dpwr and acquire spectra until the irradiated peak is 50% of the intensity without irradiation.

6. Write down the current value of dof (the sample peak frequency). To obtain a control spectrum with a control frequency, position the cursor in an empty region of the spectrum and type sd. Then type dof=<sample peak frequency>,<control frequency> to create an array of dof values.

7. Set nt = 10 to 100 times the number of transients normally collected for a ¹H spectrum of this sample. nt must also be a multiple of 32. Quantitative NOE measurements require excellent signal/noise and large nt---see Table 1.

8. To collect the spectrum, type il='y' bs=8 gain='y' ai ga.

9. Save the data.

Processing the Spectra

1. If you are in experiment 5, join another experiment. Verify that users of the VXR data station are NOT using experiment 5. Then type clradd.

2. Load your 1D NOE data and type lb=0.5 wft ds(1). Phase the spectrum.

3. Type spadd to add this spectrum to the add/subtract data buffer.

4. Type ds(2), phase the spectrum, and type spadd.

5. type addi to display the add/subtract menu. Click on sub to subtract the second spectrum (the control spectrum in ***) from the first spectrum (NOE spectrum in ***).

6. Click on select to select the difference spectrum (NOE Difference spectrum in ***). Adjust the scale of the difference spectrum using the middle mouse button.

7. Click on save to transform the difference spectrum into a real data set in experiment 5. Then save the data to the disk by clicking on main menu, file, setting your directory, and clicking on load.

nt	S/N	N/S, or % error	% error of 1% NOE	expt. time
1
2
4
8
16
32
64
128
256
512
1024
2048
4096
8192
163