On the Performance of Spin Diffusion NMR Techniques in Oriented Solids: Prospects for Resonance Assignments and Distance Measurements from Separated Local Field Experiments (original) (raw)
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1H/31P distance determination by solid state NMR in multiple-spin systems
Solid State Nuclear Magnetic Resonance, 2005
The results of two techniques of dipolar recoupling, REDOR and CPMAS, are compared in the case of a coupled multiple-spin system. A fundamentally different behavior is observed for these two techniques. In REDOR, the terms associated with each interaction S-I(k) commute with each other and no truncation takes place so that each addition of spin I(k) causes a splitting with its dipolar frequency. In CPMAS, the flip-flop terms of the dipolar Hamiltonian do not commute with the dominant term from the strongly coupled spin pair so that the weak coupling terms from the neighboring spin I(k) are effectively truncated by the dominant pair interaction. Spin dynamics calculations are in agreement with the experimental data in a cubane shaped cluster.
Journal of Biomolecular NMR, 2019
Magic angle spinning (MAS) solid-state NMR (ssNMR) spectroscopy is a major technique for the characterization of the structural dynamics of biopolymers at atomic resolution. However, the intrinsic low sensitivity of this technique poses significant limitations to its routine application in structural biology. Here we achieve substantial savings in experimental time using a new subclass of Polarization Optimized Experiments (POEs) that concatenate TEDOR and SPECIFIC-CP transfers into a single pulse sequence. Specifically, we designed new 2D and 3D experiments (2D TEDOR-NCX, 3D TEDOR-NCOCX, and 3D TEDOR-NCACX) to obtain distance measurements and heteronuclear chemical shift correlations for resonance assignments using only one experiment. We successfully tested these experiments on N-Acetyl-Val-Leu dipeptide, microcrystalline U-13 C, 15 N ubiquitin, and single-and multi-span membrane proteins reconstituted in lipid membranes. These pulse sequences can be implemented on any ssNMR spectrometer equipped with standard solid-state hardware using only one receiver. Since these new POEs speed up data acquisition considerably, we anticipate their broad application to fibrillar, microcrystalline, and membrane-bound proteins.
The Journal of Physical Chemistry B, 2000
This paper presents theoretical rotational-echo double-resonance (REDOR) and transferred-echo doubleresonance (TEDOR) curves calculated for several three-spin systems and explores the potential for determining reliable distances in multiple-spin systems of unknown geometry. These NMR techniques can provide distances which compare very well with those obtained by X-ray diffraction if the samples contain isolated heteronuclear (IS) spin pairs and are currently being used in structural investigations of solids including peptides, polymers, and inorganic materials. The situation is less clear when small clusters of spins (e.g., I N S systems) are present, and although the multispin dephasing can be calculated, very few examples have been reported in the literature. In most cases the spin system geometry was known before analysis of the NMR data, thus it is unclear whether reliable distances can be determined when the geometry of the spin system is completely unknown. To investigate the uniqueness of distance determinations from fitting of multispin REDOR and TEDOR data, the theoretical dephasing was calculated for a selection of I 2 S systems. The effects of varying the two IS dipolar couplings and the I AS -I B angle, , were studied. The full range of (0°e e 180°) was considered, and the magnitudes of the dipolar couplings selected are typical of couplings expected for commonly studied nuclei. A variation of 10°or more is required to effect a noticeable change and the dephasing is identical for and 180°-. The most distinctive behavior is observed when is small (or close to 180°), otherwise there are quite minor differences. Spin systems with quite different geometries may exhibit very similar dephasing, and in some cases the curves are identical to those for an isolated IS spin pair. These calculations indicate that it is highly unlikely that reliable distances can be obtained directly from REDOR and TEDOR experiments on multiple spin systems when the number of spins and their geometrical arrangement is completely unknown. Furthermore, it is possible to obtain incorrect distances if isolated spin pairs are assumed and multiple spins are present.
Triple oscillating field technique for accurate distance measurements by solid-state NMR
The Journal of Chemical Physics, 2008
We present a new concept for homonuclear dipolar recoupling in magic-angle-spinning (MAS) solid-state NMR experiments which avoids the problem of dipolar truncation. This is accomplished through the introduction of a new NMR pulse sequence design principle: the triple oscillating field technique. We demonstrate this technique as an efficient means to accomplish broadband dipolar recoupling of homonuclear spins, while decoupling heteronuclear dipolar couplings and anisotropic chemicals shifts and retaining influence from isotropic chemical shifts. In this manner, it is possible to synthesize Ising interaction (2IzSz) Hamiltonians in homonuclear spin networks and thereby avoid dipolar truncation—a serious problem essentially all previous homonuclear dipolar recoupling experiments suffer from. Combination of this recoupling concept with rotor assisted dipolar refocusing enables easy readout of internuclear distances through comparison with analytical Fresnel curves. This forms the basi...
From Angstroms to Nanometers: Measuring Interatomic Distances by Solid-State NMR
Chemical Reviews, 2021
Internuclear distances represent one of the main structural parameters in molecular structure determination using solid-state NMR spectroscopy, complementing chemical shifts and orientational restraints. Although a large number of magic-angle-spinning (MAS) NMR techniques have been available for distance measurements, traditional 13 C and 15 N NMR experiments are inherently limited to distances of a few angstroms due to the low gyromagnetic ratios of these nuclei. Recent development of fast MAS triple-resonance 19 F and 1 H NMR probes has stimulated the design of MAS NMR experiments that measure distances in the 1-2 nm range with high sensitivity. This review describes the principles and applications of these multiplexed multidimensional correlation distance NMR experiments, with an emphasis on 19 Fand 1 H-based distance experiments. Representative applications of these long-distance NMR methods to biological macromolecules as well as small molecules are reviewed.
A Method for Measuring Heteronuclear ( 1 H− 13 C) Distances in High Speed MAS NMR
Journal of the American Chemical Society, 2000
Magic angle spinning (MAS) NMR structure determination is rapidly developing. We demonstrate a method to determine 1 H-13 C distances r CH with high precision from Lee-Goldburg cross-polarization (LG-CP) with fast MAS and continuous LG decoupling on uniformly 13 C-enriched tyrosine‚HCl. The sequence is γ-encoded, and 1 H-13 C spin-pair interactions are predominantly responsible for the polarization transfer while proton spin diffusion is prevented. When the CP amplitudes are set to a sideband of the Hartmann-Hahn match condition, the LG-CP signal builds up in an oscillatory manner, reflecting coherent heteronuclear transfer. Its Fourier transform yields an effective 13 C frequency response that is very sensitive to the surrounding protons. This 13 C spectrum can be reproduced in detail with MAS Floquet simulations of the spin cluster, based on the positions of the nuclei from the neutron diffraction structure. It is symmetric around ω ) 0 and yields two well-resolved maxima. Measurement of CH distances is straightforward, since the separation ∆ω /2π between the maxima for a single 1 H-13 C pair is related to the internuclear distance according to r CH ) a(∆ω/2π) -1/3 , with a ) 25.86 ( 0.01 Å Hz 1/3 . For the 1 H directly bonded to a 13 C, the magnetization is transferred in a short time of ∼100 µs. After this initial rapid transfer period, the COOH, OH, or NH 3 that are not directly bonded to a 13 C transfer magnetization over long distances. This offers an attractive route for collecting long-range distance constraints and for the characterization of intermolecular hydrogen bonding.
Simple and accurate determination of X–H distances under ultra-fast MAS NMR
Journal of Magnetic Resonance, 2013
We demonstrate that a very simple experiment, Cross-Polarization with Variable Contact-time (CP-VC), is very efficient at ultra-fast MAS (ν R ≥ 60 kHz) to measure accurately the C-H and N-H distances, and to analyze the dynamics of bio-molecules. This experiment can be performed with samples that are either 13 C or 15 N labeled or without any labeling. The method is very robust experimentally with respect to imperfect Hartman-Hahn setting, and presents a large scaling factor allowing a better dipolar determination, especially for long C-H or N-H distances, or for CH 3 or NH 3 moieties with three-site hopping. At ultra-fast MAS, it can be used quantitatively in a 2D way, because its scaling factor is then little dependent on the offsets. This robustness with respect to offset is related to the ultra-fast spinning speed, and hence to the related small rotor diameter. Indeed, these two specifications lead to efficient n = ±1 zero-quantum Hartman-Hahn CP-transfers with large rf-fields on proton and carbon or nitrogen channels, and large dipolar scaling factor. R = 60 kHz, 1H = 100 kHz, 1C = 160 kHz. Slices along F1 are shown for signals at: either 123.7 (b) or 125.1 ppm (c), with aromatic CH residues of Tyr and Phe, respectively. The phenyl ring of Tyr is static, while that of Phe residue undergoes fast molecular motions. Schematic drawing of the pulse sequences used in this work for measuring X-1 H dipolar couplings: (a) CP-VC, (b) CP-PI, and (c) PISEMA. Meaning of abbreviations: CT-contact time, VCT-variable contact time, PI-phase inversion, SEMA-Spin Exchange at the Magic Angle.
Journal of Magnetic Resonance, 1999
Simple modifications of the rotational resonance experiment substantially reduce the total experimental time needed to measure weak homonuclear dipolar couplings, a critical factor for achieving routine internuclear distance measurements in large biomolecular systems. These modifications also address several problems cited in the literature. Here we introduce a constant-time rotational resonance experiment that eliminates the need for control spectra to correct for effects from variable RF heating, particularly critical for accurate long-distance measurements. This reduces the total number of experiments needed by as much as a factor of 2. Other improvements incorporated include achieving selective inversion with a delay rather than a weak pulse (P. R , which we observe results in the elimination of oscillations in peak intensities for short mixing time points. This reduces the total experiment time in two ways. First, there is no longer a need to average different "zero"-time points (S. O. Smith et al., Biochemistry 33, 6334 -6341, 1994) to correct for intensity variations. Second, short-mixing-time lineshape differences observed in large membrane-bound proteins only appear with the weak-pulse inversion and not when using the delay inversion. Consistent lineshapes between short and long mixing times permit the use of a single spectrum for subtraction of natural abundance background signals from all labeled-protein time points. Elimination of these effects improves the accuracy and efficiency of rotational resonance internuclear distance measurements.