User Manual Version 002 BRUKER BIOSPIN 119 (327)
8
FSLG-HETCOR 8
This chapter discusses setup and use of the Frequency Switched Lee Goldburg
Heteronuclear Correlation (FSLG HETCOR) experiment.
The FSLG Hetcor experiment correlates
1
H chemical shifts with X-nuclei (e.g.
13
C,
15
N) chemical shifts. The experiment provides excellent
1
H resolution in the
indirect dimension. Homonuclear decoupling in the
1
H evolution period is
achieved with an FSLG pulse train. FSLG permits relatively high spinning speeds
and makes this experiment available for high field systems, requiring high spin
-
ning speeds in order to move spinning sidebands out of the spectral region. De-
coupling the protons from the coupled X-nucleus during evolution is not essential,
since the high spinning speed already achieves that. One can however improve
the heteronuclear decoupling by a π-pulse in the middle of the evolution period
(see A. Lesage et. al.).
Mixing is achieved during the cross polarization contact time. Since magnetization
transfer from protons to X (e.g.
13
C) occurs rapidly, contact times should be kept
short in order to avoid long range transfer, leading to unspecific cross peak pat
-
terns since the magnetization then has time to flow from any proton to any X-nu-
cleus. A modification of the basic sequence uses cross polarization under a LG
frequency offset for the protons. In this case, the proton magnetization detected
by the X-nucleus comes from close protons only, since the proton spin lock at an
LG offset interrupts the “communication” between the proton spins. A third modifi
-
cation of the basic sequence uses phase modulated pulses instead of frequency
shifts. These three modifications to the basic sequence are described in
"Modifi-
cations of FSLG HETCOR".
References:
1. H.J.M. deGroot, H. Förster, and B.-J. van Rossum, Method of Improving the Resolution in Two-Di-
mensional Heteronuclear Correlation Spectra of Solid State NMR, United States Patent No 5,926.023,
Jul. 20, 1999.
2. B.-J. van Rossum, H. Förster, and H.J.M. deGroot, High-field and high-speed CP-MAS
13
C NMR Het-
eronuclear dipolar-correlation spectroscopy of solids with frequency-switched Lee-Goldburg homonu-
clear decoupling, J. Magn. Reson. A 120, 516-519 (1997).
3. B.–J. van Rossum, Structure refinement of photosynthetic components with multidimensional MAS
NMR dipolar correlation spectroscopy, Thesis, University of Leiden, Holland; (2000).
4. B.–J. van Rossum, C.P. deGroot, V. Ladizhansky, S. Vega, and H.J.M. deGroot, A Method for Measur-
ing Heteronuclear (
1
H-
13
C) Distances in High Speed MAS NMR, J. Am. Chem. Soc. 122, 3465-3472
(2000).
5. D.P. Burum and A. Bielecki, An Improved Experiment for Heteronuclear-Correlation 2D NMR in Sol-
ids, J. Magn. Res. 94, 645-652 (1991).
6. A. Lesage and L. Emsley, Through-Bond Heteronuclear Single-Quantum Correlation Spectroscopy in
Solid-State NMR, and Comparison to Other Through-Bond and Through-Space Experiments, J.
Magn. Res. 148, 449-454 (2001).
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