Frequency-switched pulse sequences: Homonuclear decoupling and dilute spin NMR in solids

Bielecki, Anthony; Kolbert, Andrew C.; Levitt, Malcolm H.

doi:10.1016/0009-2614(89)87166-0

Cited by 458 publications

(473 citation statements)

References 19 publications

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“…Fast magic-angle spinning, especially in combination with isotopic dilution, will lead to direct improvements in experimental efficiency in these cases. Moreover techniques involving tailored rf pulse sequences, such as FSLG, 47 PMLG, 48 and DUMBO, 49 are, in principle, capable of suppressing the 1 H dipolar couplings with much greater efficiency than simple MAS ͑albeit at the cost of significantly increased experimental complexity͒. We are currently applying the same principles used in this study to the challenging problem of understanding 1 H resolution under both MAS and rf irradiation.…”

Section: Discussionmentioning

confidence: 99%

Origins of linewidth in H1 magic-angle spinning NMR

Zorin

Brown

Hodgkinson

2006

The Journal of Chemical Physics

127

116

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A detailed study of the factors determining the linewidth (and hence resolution) in H1 solid-state magic-angle spinning NMR is described. Although it has been known from the early days of magic-angle spinning (MAS) that resolution of spectra from abundant nuclear spins, such as H1, increases approximately linearly with increasing sample rotation rate, the difficulty of describing the dynamics of extended networks of coupled spins has made it difficult to predict a priori the resolution expected for a given sample. Using recently developed, highly efficient methods of numerical simulation, together with experimental measurements on a variety of test systems, we propose a comprehensive picture of H1 resolution under MAS. The “homogeneous” component of the linewidth is shown to depend primarily on the ratio between an effective local coupling strength and the spin rate, modified by geometrical factors which loosely correspond to the “dimensionality” of the coupling network. The remaining “inhomogeneous” component of the natural linewidth is confirmed to have the same properties as in dilute-spin NMR. Variations in the NMR frequency due to chemical shift effects are shown to have minimal impact on H1 resolution. The implications of these results for solid-state NMR experiments involving H1 and other abundant-spin nuclei are discussed.

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Section: Discussionmentioning

confidence: 99%

Origins of linewidth in H1 magic-angle spinning NMR

Zorin

Brown

Hodgkinson

2006

The Journal of Chemical Physics

127

116

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“…114 - 116 The performance of C5 1 1 is acceptable if it is used together with a basic element C with good local averaging properties for the homonuclear DD interactions. The frequency-switched Lee-Goldburg (FSLG) 17 and MREV 14,15 sequences have both been used. 114 -116 Nevertheless, one expects some interference from the homonuclear DD couplings in the C5 1 1 -based methods.…”

Section: γ -Encoded Heteronuclear Recouplingmentioning

confidence: 99%

“…Advances in digital electronics made possible new approaches, such as the frequencyswitched Lee-Goldburg (FSLG) method. 17 These methodological developments were accompanied by important theoretical advances such as the average Hamiltonian theory and its variants. 13,14, 18 For much of this period, the spatial and spin manipulations were treated separately.…”

Section: Introductionmentioning

confidence: 99%

Symmetry‐Based Pulse Sequences in Magic‐Angle Spinning Solid‐State NMR

Levitt

2003

ChemInform

181

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“…The amide 1 H chemical shift must be carefully assigned. By using an NMR technique to measure the high-resolution solid-state 1 H NMR designed with the FSLG-2 homonuclear dipolar decoupling method [103][104][105][106] combined with high-speed MAS, the high-resolution solid-state 1 H NMR spectra of amino acids, peptides and polypeptides have been obtained with more reasonable resolution for the amide 1 H signals. The chemical shifts of the amide 1 H provide information about the hydrogen-bonded structure, compared with other high-resolution solid-state 1 H NMR methods.…”

Section: Isotropic 1 H Chemical Shiftsmentioning

confidence: 99%

Some aspects of the NMR chemical shift/structure correlation in the structural characterization of polymers and biopolymers

Ando

2012

Polym J

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Studies on the NMR methodology for characterizing the structure of polymers and biopolymers based on the understanding of the NMR chemical shift/structure correlation using solution-state and solid-state NMR experiments, the development of the NMR chemical shift theory and their combination have been reviewed. Polymer Journal (2012) 4 and Johnsen and Tessmar 5 independently reported a very important discovery for polymer science: the a-CH 3 signals in the 1 H NMR spectrum of poly(methyl methacrylate)s with different tacticities in chloroform solution appear at different chemical shift positions, in which the three splitting signals were assigned to the rr, mr and mm triads from upfield on the basis of sophisticated and reasonable experiments, where m and r are the meso and racemic dyads, respectively. Since that time, NMR spectroscopy has been well recognized to be the most powerful method available for characterizing the structures of polymers. This means that the chemical shift (chemical shielding), as one of the important NMR parameters, 6 can be meaningfully used for the structural characterization of polymers.With such a foundation, the sophisticated understanding and development of the NMR chemical shift/structure correlation for the structural characterization of polymers and biopolymers have been implemented as one of our research programs. In this review, it is shown by the author and his colleagues that understanding the NMR chemical shift/structure correlation provides a powerful methodology for the structural characterization of polymers and biopolymers based on the sophisticated development of solution-state and solid-state NMR experiments, the development of NMR chemical shift theory, and their combination. 7,8 THE CONCEPT OF THE NMR CHEMICAL SHIFT/STRUCTURE CORRELATION A polymer chain has an enormous number of chemical bonds. In the solution state, the NMR chemical shifts of polymers are generally the averaged values over all of the possible conformations because of the rapid interconversions by rotation around the chemical bonds. However, in solids, the chemical shifts are often characteristic of specific conformations because of strongly restricted rotation around the bonds. 7,8 The NMR chemical shift is affected by a change in the electronic structure caused by the conformational change. Solid-state NMR chemical shifts, therefore, provide useful information about the electronic structure of a polymer chain and multiple polymer chains with a fixed structure. Furthermore, the complete chemical shift tensor components can often be determined because the chemical shift is, in principle, the second-rank tensor quantity. The complete chemical shift tensor components (the chemical shift anisotropy) of polymers and biopolymers provide information about the local symmetry of the electron cloud around the nucleus, and therefore, provide much more detailed knowledge about the conformation associated with electronic structure compared with the averaged chemical shift. To completely understand the NMR ch...

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Frequency-switched pulse sequences: Homonuclear decoupling and dilute spin NMR in solids

Cited by 458 publications

References 19 publications

Origins of linewidth in H1 magic-angle spinning NMR

Origins of linewidth in H1 magic-angle spinning NMR

Symmetry‐Based Pulse Sequences in Magic‐Angle Spinning Solid‐State NMR

Some aspects of the NMR chemical shift/structure correlation in the structural characterization of polymers and biopolymers

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