2D TOCSY Experiment

This two-dimensional phase-sensitive TOCSY experiment helps reduce diagonal peaks when lines are broad. Before setting up the TOCSY experiment, see Acquiring and Processing 2D Experiments. See the Varian Guide to NMR Experiments for a complete description of this experiment.

Acquiring the experiment:

  1. Join the experiment in which the 1H reference spectrum was collected.
  2. Type tocsy.
  3. Type dg. Adjust the parameters in bold listed below for the standard TOCSY:
    sfrq=
    tn=H1
    at = set by spectrometer
    np=2048
    sw = sw from 1H reference spectrum
    ss=2
    pw = 1 / [(sw*sfrq)*4]
    tpwr = set up an array experiment and measure based on pw above
    p1 = 1H 90° pulse width listed at console
    p1lvl = 56
    d1 = 1H relaxation delay (1-2 * 1H T1)
    d2=0
    presat='n'
    mix=0.2 to 0.5 (see next page)
    tof = tof from 1H reference spectrum
    nt = multiple of 8
    ct = set by computer
    dm='n'
    sw1 = sw from 1H reference spectrum
    ni = multiple of 64
    dp='y'
    hs='n'
    sspul='n'
    phase=1,2
    presat = 'n'
    mix = 0.01 to 0.05 based on your molecule
    nowt
    fn = np
    fn1 = 512
    ***TURN OFF SPINNER***
    temp=30 su -- to set variable temperature to 30 degrees
    au to start acquisition

    Typical values are listed below for sw1=4400 and mix=0.5:
    d1 ni
    nt
    time
    vert. res
    d1
    ni
    nt
    time
    vert. res

    1.5
    128
    8
    1:18
    17.2 Hz
    1.5
    128
    64
    10:17
    17.2 Hz

    1.5
    256
    8
    2:37
    8.6
    1.5
    256
    64
    20:42
    8.6

    1.5
    512
    8
    5:15
    4.3
    1.5
    512
    64
    41:56
    4.3

    1.5
    128
    16
    2:34
    17.2
    2.25
    128
    8
    1:42
    17.2

    1.5
    256
    16
    5:11
    8.6
    2.25
    256
    8
    3:30
    8.6

    1.5
    512
    16
    10:29
    4.3
    2.25
    512
    8
    6:59
    4.3

    Processing, Displaying, and Plotting:

    Process using the procedure for Processing a 2D Phase-Sensitive Experiment. Plot All Contours. The NOESY spectrum may be symmeterized by typing foldt.

    Setting mix, the NOE mixing time paramter

    mix is the time period (in seconds) during which magnetization is transferred from one 1H to another 1H. mix must be long enough to transfer magnetization between spins to "build up" the NOESY cross peak intensity between the two spins. If mix is too long, the magnetization transferred to the second 1H will "diffuse" to additional spins, decreasing the NOESY cross-peak intensity between the two spins and creating new cross peaks between spins that are farther apart than 5A. Typical values for mix range from 0.2 to 0.5 seconds depending upon the sample's molecular weight.

    Phasing:

    see page 300 in Varian Manual

    phasing pmode = full

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    Last updated: April 1st, 1998
    URL: http://nmr.chem.indiana.edu/NMRguide/2dexpt/tocsy.html
    Copyright 1996, The Trustees of Indiana University