Multiplicity edited HMBC

The edited HMBC experiment edits into two subspectra according to the number of protons attached to 13C nuclei being odd or even.

Sequence

a) Standard sequence


b) Up-down sequence

HMBC pulse sequences with a 3rd order low-pass J filter for editing into two subspectra according to the number of directly attached protons being odd or even:

Filled and open bars refer to pi /2 and pi pulses, respectively, while the dashed box represents 13C decoupling. tau = (2×1JCH)-1 and delta is the delay necessary for a gradient.

The initial four gradients of the low-pass J filter can be set an order of magnitude weaker than the other gradients for formation of heteronuclear gradient echoes.

The recommended phase cycle is:

  • phi 1 = {x, -x, -x, x},
  • phi 2 = {x, x, 4(-x), x, x},
  • phi 3 = {4(x), 4(y), 4(-x), 4(-y)},
  • with receiver phase {x, -x}.

The delays for the 3rd order low-pass J filter is

  • tau 1 = ½ [1Jmin + 0.07(1Jmax - 1Jmin)]-1,
  • tau = tau 2 = [1Jmax + 1Jmin]-1,
  • tau 3 = ½ [1Jmax - 0.07(1J max - 1Jmin)]-1.

a) Standard HMBC pulse sequence where the echo is selected by the filled gradients and the antiecho by the open gradients;

b) up-down HMBC pulse sequence inverting 13CH and 13CH3 peaks relative to the standard sequence and where the echo is selected by the +5G/-5G gradients and the antiecho by the -3G /+3G gradients.

References

  • Nils T. Nyberg and Ole W. Sørensen Multiplicity-edited Broadband HMBC NMR spectra Magnetic Resonance in Chemistry xx in press 2006

  • Schulte-Herbrüggen, T., Meissner, A., Papanikos, A., Meldal, M., and Sørensen, O.W. Optimizing delays in the MBOB, broadband HMBC, and broadband XLOC NMR pulse sequences J.Magn.Reson. 156 282-294 2002

Code and procedures

For Bruker. The Varian code is incorporated into the improved edited HMBC and can be downloaded from here

 
Document: Edited HMBC (index.shtml)
Last modified: 2006-05-24