High-resolution 1H NMR in solids with frequency-switched multiple-pulse sequences

Levitt, Malcolm H.; Kolbert, Andrew C.; Bielecki, Anthony; Ruben, D. J.

doi:10.1016/0926-2040(93)90021-e

Cited by 124 publications

(92 citation statements)

References 19 publications

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“…For other systems where deuterated derivatives need to be synthesized chemically, this route is less common due to a more resource intensive nature of the approach. On the other hand, CRAMPS methods achieved a remarkable feat of efficient averaging of the 1 H-1 H dipolar couplings even under moderate spinning frequencies [16][17][18][19][20][21][22][23][24][25]. Thanks to this, investigations on uniformly protonated compounds have become increasingly popular in the recent years [18,21,[26][27][28][29][30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 99%

1H line width dependence on MAS speed in solid state NMR – Comparison of experiment and simulation

Sternberg

Witter

Kuprov

et al. 2018

Journal of Magnetic Resonance

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b s t r a c tRecent developments in magic angle spinning (MAS) technology permit spinning frequencies of !100 kHz. We examine the effect of such fast MAS rates upon nuclear magnetic resonance proton line widths in the multi-spin system of b-Asp-Ala crystal. We perform powder pattern simulations employing Fokker-Plank approach with periodic boundary conditions and 1 H-chemical shift tensors calculated using the bond polarization theory. The theoretical predictions mirror well the experimental results. Both approaches demonstrate that homogeneous broadening has a linear-quadratic dependency on the inverse of the MAS spinning frequency and that, at the faster end of the spinning frequencies, the residual spectral line broadening becomes dominated by chemical shift distributions and susceptibility effects even for crystalline systems.

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Section: Introductionmentioning

confidence: 99%

1H line width dependence on MAS speed in solid state NMR – Comparison of experiment and simulation

Sternberg

Witter

Kuprov

et al. 2018

Journal of Magnetic Resonance

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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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“…The first 90° pulse generates transverse 1 H magnetization that evolves perpendicular to the effective field of the homonuclear decoupling sequence applied during the evolution interval t 1 . We used both FSLG [10], [11] and [12] and eDUMBO [20] windowless homonuclear decoupling, whose effective fields enclose an angle of close to the magic-angle of 54.74° with respect to the z-axis in the rotating frame. Therefore, the following pulse rotates the magnetization into the xyplane.…”

Section: Solid-state Nmr Experimentsmentioning

confidence: 99%

“…Although ultrafast MAS leads to considerably improved proton resolution by attenuating the influence of the strong 1 H-1 H couplings, better results can so far still be achieved by combining MAS with applying homonuclear dipolar decoupling sequences to enhance the averaging of the 1 H homonuclear dipolar couplings [8] and [9]. The homonuclear decoupling sequences Frequency-Switched Lee-Goldburg (FSLG) [10], [11] and [12] and its close relative Phase-Modulated Lee-Goldburg (PMLG) [13], [14] and [15] are based on theoretical arguments by average Hamiltonian [16] and Floquet theory [17] to suppress the homonuclear dipolar 1 H-1 H couplings and their commutators with other spin interactions to a certain order. The DUMBO ('decoupling using mind-boggling optimization') sequence has been developed by numerical optimization using a two-spin system [18] and [19].…”

mentioning

confidence: 99%

Proton micro-magic-angle-spinning NMR spectroscopy of nanoliter samples

Brinkmann

Vasa

Janssen

et al. 2010

Chemical Physics Letters

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High-resolution 1H NMR in solids with frequency-switched multiple-pulse sequences

Cited by 124 publications

References 19 publications

1H line width dependence on MAS speed in solid state NMR – Comparison of experiment and simulation

1H line width dependence on MAS speed in solid state NMR – Comparison of experiment and simulation

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

Proton micro-magic-angle-spinning NMR spectroscopy of nanoliter samples

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