Acquiring 1D NOE on a Varian InovaAcquiring 1D NOE on a Varian Inova

CycleNOE:

Cyclenoe is the standard steady-state NOE difference technique for Inova spectrometers. The equivalent for Gemini spectrometers is noedif

Set up appropriate 1H parameters. Normally should acquire 1D 1H spectrum first.

pw = 1H pulse, should be 90º pulse

tpwr = high power for 1H; should be set according to pw, or is correlated to pw.

satfrq = frequency to saturate for NOE; can be determined by putting cursor on peak to saturate and typing sd (set decoupler). Then, read value. Set satfrq = that value.

control = frequency for off-resonance saturation (where there are no peaks). This will be used for data subtraction. This can be set in the same way as satfrq; find a point where there are no peaks, type sd, then read value and set
control = that value. It is preferable for control to be close to the satfrq to be sure all conditions are the same (particularly no off resonance effects)

intsub = internal subtraction of data; if intsub = 'y' then data is subtracted every other scan, else if insub = 'n' then data is stored separately. intsub ='y' is preferable

pattern = the pattern of the multiplet = 1 for singlet, 2 for doublet ...

spacing = spacing between lines of the mutliplet

cycle = whether you are going to cycle through various lines of a multiplet. The advantage is that with cycle turned on then there is more even saturation of the whole resonance. Normally, cycle = 'y'

tau = time spent on a single irradiation point during cycling (cycling cycles what part of multiplet is irradiated), usually ~100 ms

satpwr = power of saturation (from -16 to 3) higher power will saturate over a larger frequency range. Low power may not fully saturate the resonance. Standard value ~-10.

sattime = length of time for saturation = saturate too long and there are many indirect NOEs, not long enough and the signal-to-noise is low. Sattime can be set to hundreds of milliseconds to seconds. NOE buildup is T1 dependent.

array = an array of satfrq, pattern and spacing for proper number of experiments (for more than 1 NOE experiment)

nt = a multiple of 16

d1 = ~1 second

at = acquisition time; longer acquisition time gives higher resolution, but takes longer to acquire, so normally ~4 seconds as in standard 1D

sw = spectral width, should be large enough to cover all proton resonances

tof = transmitter offset, center of 1H spectrum

solvent should be set appropriately

np = number of points, is set by setting at and sw

bs = block size; data will be written after block size is reached, so you cannot accidentally acquire an odd number of scans, or an incomplete phase cycle. If bs =1 then you will see where you are saturating, to be sure you have picked the right peak; if you set bs = 32 then you can be sure to process data only after
the full phase cycle


Steps to acquire

1) acquire 1D, set sw, tof, np, at, pw, tpwr

2) type cyclenoe

3) measure control and satfrq

4) input pattern and spacing

5) set bs

6) acquire spectrum, type go or ga

7) spectrum should be acquired non-spinning and with temperature regulation, especially if acquisition is going to take more than a few minutes.


Data should be processed with a weighting function. Line broadening of 1-2 Hz (lb = 1) might be good to increase signal-to-noise and eliminate any truncation artifacts.