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{{bruker-pulse-sequence
|name=hmbcacbigpl2ndqf
|synopsis=STAR-HMBC
|family=[[2D HMBC]]
|medium=Liquids
|author=
|dim=2
|nuclei=HX
|observe=H
|comment=documented revision 1.11.2.3
}}
[[Category:HMBC]]
[[Category:Small molecule]]

==Introduction==
The '''hmbcacbigpl2ndqf''' is a pulse sequence for Bruker epuipment. It is a variation of 2D HMBC technique where it is possible to differentiate <sup>2</sup>J<sub>CH</sub> and <sup>3</sup>J<sub>CH</sub> correlations<cite>star-hmbc</cite>. It's very useful in structural elucidation of natural products. A drawback of this experiment is the lower sensitivity detection compared to the common HMBC.

==Delays==
'''d1''' - recycling delay (1-5 x T1) (usually 2 s)

'''d2''' - Calculed autmatically based in cnst2

'''d6''' - Calculed autmatically based in cnst14 - evolution of long range coupling. (83 ms from cnst14 = 6 Hz)

'''d16''' - gradient recovery delay (depends on the probe) may be on the order of 100-500 &mu;s.

==Acquisition in the indirect dimension and number of scans==

The incremented delay used to record evolution in the indirect dimension is 2x'''d0'''. '''d0''' is automatically calculated within the experiment using '''in0'''. 

'''in0''' equals 1/(2*SW) one half of the inverse of the spectral window width in X dimension. (1/2) is due to '''nd0'''=2 (below).

'''td1''' - number of experiments to record in the X dimension

'''nd0''' = 2 - there are two delays '''d0''' within the X dimension evolution delay.

'''ns''' - number of scans must be a multiple of 8.

==Carrier frequencies==
'''O1''' (or '''O1P''' for the value in ppm)  - in the middle of <sup>1</sup>H spectrum.

'''O2''' (or '''O2P''' for the value in ppm)  - in the middle of <sup>13</sup>C spectrum.

==Hard RF pulses==

==={{1H}} channel===

'''p1''' - hard {{1H}} {{90}} at power level '''pl1''' - the only {{1H}} to set up for this experiment. Length of {{180}} pulse ('''p2''') is calculated automatically.

===X-nucleus channel===

'''p3''' - hard X-nucleus {{90}} at power level '''pl2'''.

====Shaped 180 pulses====
This sequence has two shaped 180 pulses at the X-nucleus channel - '''p14''' and '''p24'''

'''p14''' - is a refocusing pulse at power level '''sp3'''.

'''spnam3''' must be set to the name of the waveform file.

'''p14''' of 500&mu;s is recommended for '''spnam3''' set to '''Crp60,0.5,20.1'''.

If waveform '''Crp60,0.5,20.1''' are not available on the system they need to be prepared using the '''stdisp''' tool or an appropriate replacement used instead.

==Gradient pulses==

'''Duration''' of all gradients is set by:

* '''p16''' (recommended default - 1 ms)

'''Shapes''' of all gradients are recommended to be '''sine bell''' implemented in 100 steps, i.e.:

* '''gpnam1''' '''SINE.100'''
* '''gpnam2''' '''SINE.100'''
* '''gpnam3''' '''SINE.100'''
* '''gpnam4''' '''SINE.100'''
* '''gpnam5''' '''SINE.100'''
* '''gpnam6''' '''SINE.100'''
* '''gpnam7''' '''SINE.100'''
* '''gpnam8''' '''SINE.100'''

'''Strengths''' of gradients are set by parameters:

* '''gp1''':'''gp2''':'''gp3''':'''gp4''':'''gp5''':'''gp6''':'''gp7''':'''gp8''' - 50:30:40.1:60:-40:-20:11:-11

==Setup Constants==

* '''cnst2''' - coupling constant for <sup>1</sup>J<sub>CH</sub> (recommended - 145 Hz)

* '''cnst6''' - minimal coupling constant for <sup>1</sup>J<sub>CH</sub> (recommended - 125 Hz)

* '''cnst7''' - maximum coupling constant for <sup>1</sup>J<sub>CH</sub> (recommended - 165 Hz)

* '''cnst14''' - minimal coupling constant for  long range J<sub>CH</sub> (recommended - 6 Hz)

* '''cnst15''' - maximum coupling constant for  long range J<sub>CH</sub> (recommended - 10 Hz)

* '''cnst16''' - scaling factor for splitting pattern of the multiples (recommended - 15-24)

==References==
<biblio>
#star-hmbc bibtex=@article{krishnamurthy20002j,
  title={{2J, 3J-HMBC: a new long-range heteronuclear shift correlation technique capable of differentiating 2JCH from 3JCH correlations to protonated carbons}},
  author={Krishnamurthy, VV and Russell, D.J. and Hadden, C.E. and Martin, G.E.},
  journal={Journal of Magnetic Resonance},
  volume={146},
  number={1},
  pages={232--239},
  year={2000},
  publisher={Elsevier},
  url={http://dx.doi.org/10.1006/jmre.2000.2141},
}
#impeach-mbc bibtex=@article{hadden1999improved,
  title={{Improved Performance Accordion Heteronuclear Multiple-Bond Correlation Spectroscopy--IMPEACH-MBC}},
  author={Hadden, C.E. and Martin, G.E. and Krishnamurthy, VV},
  journal={Journal of Magnetic Resonance},
  volume={140},
  number={1},
  pages={274--280},
  year={1999},
  publisher={Elsevier},
  url={http://dx.doi.org/10.1006/jmre.1999.1840},
}
#cigar-hmbc bibtex=@article{hadden2000constant,
  title={{Constant time inverse-detection gradient accordion rescaled heteronuclear multiple bond correlation spectroscopy: CIGAR-HMBC}},
  author={Hadden, C.E. and Martin, G.E. and Krishnamurthy, VV},
  journal={Magnetic Resonance in Chemistry},
  volume={38},
  number={2},
  pages={143--147},
  year={2000},
  publisher={John Wiley \& Sons},
  url={http://dx.doi.org/10.1002/(SICI)1097-458X(200002)38:2&lt;143::AID-MRC624&gt;3.0.CO;2-S}
}
#accord-hmbc bibtex=@article{wagner1998accord,
  title={{ACCORD-HMBC: a superior technique for structural elucidation}},
  author={Wagner, R. and Berger, S.},
  journal={Magnetic Resonance in Chemistry},
  volume={36},
  number={S1},
  pages={S44--S46},
  year={1998},
  publisher={John Wiley \& Sons},
  url={http://dx.doi.org/10.1002/(SICI)1097-458X(199806)36:13&lt;S44::AID-OMR281&gt;3.0.CO;2-Q},
}
</biblio>
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