Origin of the residual line width under frequency-switched Lee–Goldburg decoupling in MAS solid-state NMR

Hellwagner, Johannes; Grunwald, Liam; Ochsner, Manuel; Zindel, Daniel; Meier, Beat H.; Ernst, Matthias

doi:10.5194/mr-1-13-2020

Cited by 9 publications

(19 citation statements)

References 65 publications

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“…Typically, in fully protonated solids the resolution of the 1 H spectra obtained with PMLG decoupling at slow-moderate MAS frequencies or only ∼60 kHz MAS are comparable (Figure E,G) . Ernst and co-workers have recently demonstrated that the residual line width in PMLG decoupled 1 H spectrum at slow MAS arises primarily from two sources: (i) third-order autoterm for the homonuclear couplings and (ii) the deleterious effects of RF inhomogeneity . Note that the application of these decoupling sequences results in scaling of the isotropic chemical shift Hamiltonian.…”

Section: Decoupling Under Masmentioning

confidence: 95%

“…264 Ernst and coworkers have recently demonstrated that the residual line width in PMLG decoupled 1 H spectrum at slow MAS arises primarily from two sources: (i) third-order autoterm for the homonuclear couplings and (ii) the deleterious effects of RF inhomogeneity. 271 Note that the application of these decoupling sequences results in scaling of the isotropic chemical shift Hamiltonian. In the static case, the scaling factor is cos(θ m ) = 0.577.…”

Section: Homonuclear Decouplingmentioning

confidence: 99%

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Solid-State NMR: Methods for Biological Solids

et al. 2022

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In the last two decades, solid-state nuclear magnetic resonance (ssNMR) spectroscopy has transformed from a spectroscopic technique investigating small molecules and industrial polymers to a potent tool decrypting structure and underlying dynamics of complex biological systems, such as membrane proteins, fibrils, and assemblies, in near-physiological environments and temperatures. This transformation can be ascribed to improvements in hardware design, sample preparation, pulsed methods, isotope labeling strategies, resolution, and sensitivity. The fundamental engagement between nuclear spins and radio-frequency pulses in the presence of a strong static magnetic field is identical between solution and ssNMR, but the experimental procedures vastly differ because of the absence of molecular tumbling in solids. This review discusses routinely employed state-of-the-art static and MAS pulsed NMR methods relevant for biological samples with rotational correlation times exceeding 100’s of nanoseconds. Recent developments in signal filtering approaches, proton methodologies, and multiple acquisition techniques to boost sensitivity and speed up data acquisition at fast MAS are also discussed. Several examples of protein structures (globular, membrane, fibrils, and assemblies) solved with ssNMR spectroscopy have been considered. We also discuss integrated approaches to structurally characterize challenging biological systems and some newly emanating subdisciplines in ssNMR spectroscopy.

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Section: Decoupling Under Masmentioning

confidence: 95%

Section: Homonuclear Decouplingmentioning

confidence: 99%

Solid-State NMR: Methods for Biological Solids

et al. 2022

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“…Then the reciprocal space of eq can be given via The FIDs will then be distributed in this k -space as shown schematically in Figure c, with angles varying from φ min for the fastest MAS rate to φ max for the slowest MAS rate. The angle φ is given by the ratio between the prefactor of the error terms (including residual couplings and shifts, due to imperfect averaging of dipolar couplings and chemical shift anisotropies that are responsible for the broadening in the spectra) ,− and the pure isotropic terms (isotropic chemical shifts). For a static sample φ st = 45° since ∑ m F m (ω MAS ) = 1.…”

Section: Methodsmentioning

confidence: 99%

Pure Isotropic Proton Solid State NMR

et al. 2021

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Resolution in proton solid state magic angle sample spinning (MAS) NMR is limited by the intrinsically imperfect nature of coherent averaging induced by either MAS or multiple pulse sequence methods. Here, we suggest that instead of optimizing and perfecting a coherent averaging scheme, we could approach the problem by parametrically mapping the error terms due to imperfect averaging in a k-space representation, in such a way that they can be removed in a multidimensional correlation leaving only the desired pure isotropic signal. We illustrate the approach here by determining pure isotropic 1 H spectra from a series of MAS spectra acquired at different spinning rates. For six different organic solids, the approach is shown to produce pure isotropic 1 H spectra that are significantly narrower than the MAS spectrum acquired at the fastest possible rate, with linewidths down to as little as 48 Hz. On average, we observe a 7-fold increase in resolution, and up to a factor of 20, as compared with spectra acquired at 100 kHz MAS. The approach is directly applicable to a range of solids, and we anticipate that the same underlying principle for removing errors introduced here can be applied to other problems in NMR spectroscopy.

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“…The CRAMPS technique improved proton resolution at slower MAS but has been recently demonstrated to also limit the achievable resolution. 36,381 The CRAMPS approach was demonstrated to improve resolution in protein compared to only MAS spectra at slower MAS frequencies. 382 However, the method never really became popular, mainly due to limited proton resolution, RF heating, signal loss due to windowed acquisition, and multiparameter optimization for optimum decoupling performance.…”

Section: Applications To Proteinsmentioning

confidence: 99%

Ultrafast Magic Angle Spinning Solid-State NMR Spectroscopy: Advances in Methodology and Applications

et al. 2022

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Solid-state NMR spectroscopy is one of the most commonly used techniques to study the atomic-resolution structure and dynamics of various chemical, biological, material, and pharmaceutical systems spanning multiple forms, including crystalline, liquid crystalline, fibrous, and amorphous states. Despite the unique advantages of solid-state NMR spectroscopy, its poor spectral resolution and sensitivity have severely limited the scope of this technique. Fortunately, the recent developments in probe technology that mechanically rotate the sample fast (100 kHz and above) to obtain “solution-like” NMR spectra of solids with higher resolution and sensitivity have opened numerous avenues for the development of novel NMR techniques and their applications to study a plethora of solids including globular and membrane-associated proteins, self-assembled protein aggregates such as amyloid fibers, RNA, viral assemblies, polymorphic pharmaceuticals, metal–organic framework, bone materials, and inorganic materials. While the ultrafast-MAS continues to be developed, the minute sample quantity and radio frequency requirements, shorter recycle delays enabling fast data acquisition, the feasibility of employing proton detection, enhancement in proton spectral resolution and polarization transfer efficiency, and high sensitivity per unit sample are some of the remarkable benefits of the ultrafast-MAS technology as demonstrated by the reported studies in the literature. Although the very low sample volume and very high RF power could be limitations for some of the systems, the advantages have spurred solid-state NMR investigation into increasingly complex biological and material systems. As ultrafast-MAS NMR techniques are increasingly used in multidisciplinary research areas, further development of instrumentation, probes, and advanced methods are pursued in parallel to overcome the limitations and challenges for widespread applications. This review article is focused on providing timely comprehensive coverage of the major developments on instrumentation, theory, techniques, applications, limitations, and future scope of ultrafast-MAS technology.

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Origin of the residual line width under frequency-switched Lee–Goldburg decoupling in MAS solid-state NMR

Cited by 9 publications

References 65 publications

Solid-State NMR: Methods for Biological Solids

Solid-State NMR: Methods for Biological Solids

Pure Isotropic Proton Solid State NMR

Ultrafast Magic Angle Spinning Solid-State NMR Spectroscopy: Advances in Methodology and Applications

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