STAR-HMBC for Bruker (hmbcacbigpl2ndqf)
From NMR Wiki
Basic facts about hmbcacbigpl2ndqf
Family: 2D HMBC
Copyright: Bruker, Inc.
The hmbcacbigpl2ndqf is a pulse sequence for Bruker epuipment. It is a variation of 2D HMBC technique where it is possible to differentiate 2JCH and 3JCH correlations. 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.
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 μs.
Acquisition in the indirect dimension and number of scans
The incremented delay used to record evolution in the indirect dimension is 2xd0. 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.
O1 (or O1P for the value in ppm) - in the middle of 1H spectrum.
O2 (or O2P for the value in ppm) - in the middle of 13C spectrum.
Hard RF pulses
p1 - hard 1H 90o at power level pl1 - the only 1H to set up for this experiment. Length of 180o pulse (p2) is calculated automatically.
p3 - hard X-nucleus 90o 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 500μs 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.
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
- cnst2 - coupling constant for 1JCH (recommended - 145 Hz)
- cnst6 - minimal coupling constant for 1JCH (recommended - 125 Hz)
- cnst7 - maximum coupling constant for 1JCH (recommended - 165 Hz)
- cnst14 - minimal coupling constant for long range JCH (recommended - 6 Hz)
- cnst15 - maximum coupling constant for long range JCH (recommended - 10 Hz)
- cnst16 - scaling factor for splitting pattern of the multiples (recommended - 15-24)
- Krishnamurthy, VV and Russell, DJ and Hadden, CE and Martin, GE. 2J, 3J-HMBC: a new long-range heteronuclear shift correlation technique capable of differentiating 2JCH from 3JCH correlations to protonated carbons. Journal of Magnetic Resonance 146(1):232--239, 2000. BibTeX
Hadden, CE and Martin, GE and Krishnamurthy, VV. Improved Performance Accordion Heteronuclear Multiple-Bond Correlation Spectroscopy--IMPEACH-MBC. Journal of Magnetic Resonance 140(1):274--280, 1999. BibTeX
Hadden, CE and Martin, GE and Krishnamurthy, VV. Constant time inverse-detection gradient accordion rescaled heteronuclear multiple bond correlation spectroscopy: CIGAR-HMBC. Magnetic Resonance in Chemistry 38(2):143--147, 2000. BibTeX