17O NMR Spectroscopy: A Novel Probe for Characterizing Protein Structure and Folding.
TL;DR: A review of 17O NMR spectroscopy for protein structure and folding can be found in this paper, where the authors discuss the promising advantages of this methodology over other techniques and explain why further technical and experimental advancements are highly desired.
Abstract: Oxygen is a key atom that maintains biomolecular structures, regulates various physiological processes, and mediates various biomolecular interactions. Oxygen-17 (17O), therefore, has been proposed as a useful probe that can provide detailed information about various physicochemical features of proteins. This is attributed to the facts that (1) 17O is an active isotope for nuclear magnetic resonance (NMR) spectroscopic approaches; (2) NMR spectroscopy is one of the most suitable tools for characterizing the structural and dynamical features of biomolecules under native-like conditions; and (3) oxygen atoms are frequently involved in essential hydrogen bonds for the structural and functional integrity of proteins or related biomolecules. Although 17O NMR spectroscopic investigations of biomolecules have been considerably hampered due to low natural abundance and the quadruple characteristics of the 17O nucleus, recent theoretical and technical developments have revolutionized this methodology to be optimally poised as a unique and widely applicable tool for determining protein structure and dynamics. In this review, we recapitulate recent developments in 17O NMR spectroscopy to characterize protein structure and folding. In addition, we discuss the highly promising advantages of this methodology over other techniques and explain why further technical and experimental advancements are highly desired.
Citations
More filters
TL;DR: In this paper , the authors highlight the recent advances in dipolar and chemical shift anisotropy recoupling methods, as well as their applications in structural determination and dynamical characterization at multiple time scales.
Abstract: With the development of NMR methodology and technology during the past decades, solid-state NMR (ssNMR) has become a particularly important tool for investigating structure and dynamics at atomic scale in biological systems, where the recoupling techniques play pivotal roles in modern high-resolution MAS NMR. In this review, following a brief introduction on the basic theory of recoupling in ssNMR, we highlight the recent advances in dipolar and chemical shift anisotropy recoupling methods, as well as their applications in structural determination and dynamical characterization at multiple time scales (i.e., fast-, intermediate-, and slow-motion). The performances of these prevalent recoupling techniques are compared and discussed in multiple aspects, together with the representative applications in biomolecules. Given the recent emerging advances in NMR technology, new challenges for recoupling methodology development and potential opportunities for biological systems are also discussed.
16 citations
TL;DR: In this paper , the authors used magnetically aligned polymer nanodiscs as an alignment medium to measure residual quadrupolar couplings (RQCs) for 17O-labeled benzoic acid in the aqueous phase.
Abstract: The use of 17O in NMR spectroscopy for structural studies has been limited due to its low natural abundance, low gyromagnetic ratio, and quadrupolar relaxation. Previous solution 17O work has primarily focused on studies of liquids where the 17O quadrupolar coupling is averaged to zero by isotropic molecular tumbling, and therefore has ignored the structural information contained in this parameter. Here, we use magnetically aligned polymer nanodiscs as an alignment medium to measure residual quadrupolar couplings (RQCs) for 17O-labelled benzoic acid in the aqueous phase. We show that increasing the magnetic field strength improves spectral sensitivity and resolution and that each satellite peak of the expected pentet pattern resolves clearly at 18.8 T. We observed no significant dependence of the RQC magnitudes on the magnetic field strength. However, changing the orientation of the alignment medium alters the RQC by a consistent factor, suggesting that 17O RQCs measured in this way can provide reliable orientational information for elucidations of molecular structures.
1 citations
TL;DR: In this article , the authors presented simple, fast and cost-efficient 17 O-enrichment strategies for amino acids and peptides, using mechanochemistry, which can provide unique information regarding the structure and reactivity of biomolecules.
Abstract: 17 O NMR spectroscopy is a powerful technique, which can provide unique information regarding the structure and reactivity of biomolecules. However, the low natural abundance of 17 O (0.04%) generally requires working with enriched samples, which are not easily accessible. Here, we present simple, fast and cost-efficient 17 O-enrichment strategies for amino acids and peptides, using mechanochemistry. First, five unprotected amino acids were enriched under ambient conditions, consuming only microliter amounts of costly labeled water, and producing pure molecules with enrichment levels up to ~ 40%, yields ~ 60-85%, and no loss of optical purity. Subsequently, 17 O-enriched Fmoc/ t Bu-protected amino acids were produced on a 1g/day scale with high enrichment levels. Lastly, a site-selective 17 O-labeling of carboxylic functions in peptide side-chains was achieved for RGD and GRGDS peptides, with ~ 28% enrichment level. For all molecules, 17 O ssNMR spectra were recorded at 14.1T in reasonable times, making this an important step forward for future NMR studies of biomolecules.
1 citations
01 Jan 2023
TL;DR: In this paper , the synthesis and characterization of materials with an inorganic component, such as oxides, metal-organic frameworks, and zeolites, is discussed, and illustrated.
Abstract: While the research fields of mechanochemistry and solid state NMR (ssNMR) have been developing in independent ways for many years, there are an increasing number of studies in which both topics meet. On one hand, ssNMR can be used to perform advanced characterizations of the structure, morphology and also properties of materials prepared by mechanochemistry. On the other, syntheses performed using mechanochemistry can help push forward the current frontiers of solid state NMR, for example through the development of new phases enriched in NMR-active isotopes. Lastly, studies at the interface between mechanochemistry and ssNMR are increasingly being carried out, notably to help elucidate reaction mechanisms in ball-milling (BM). In this chapter, illustrations of investigations along these lines will be provided, focusing on the synthesis and characterization of materials with an inorganic component, such as oxides, metal-organic frameworks, and zeolites, just to name a few.
TL;DR: In this article , the translocation events of a single ellipsoid human serum albumin (HSA) with a solid glass nanopore have been investigated in detail by common resistive pulses.
Abstract: In this paper, translocation events of single ellipsoid human serum albumin (HSA) with a solid glass nanopore have been investigated in detail by common resistive pulses. In particular, the translocation events can be classified into three main groups according to the significant difference in current pulse amplitudes. By adjusting the electric field of the nanopore upon changing applied conditions in voltage, pH, and pore size, the observation would be originally associated with dynamic rotation rather than increased size exclusion of HSA. Finally, the rotation angles of translocated HSA are determined by both experimental and theoretical studies.
References
More filters
TL;DR: In contrast to what happens in spin-'/2 spectroscopy, no single-axis spinning techniques are available for canceling the effects of these second-order anisotropies as discussed by the authors.
Abstract: Interest in the solid state nuclear magnetic resonance (NMR) spectroscopy of half-integer quadrupolar spins is strongly stimulated by the roles that these isotopes play in a variety of important systems such as minerals, structural ceramics, semiconductors, glasses, and catalysts.' In spite of the partly ionic nature of these materials, quadrupole interactions with surrounding electric field gradients often broaden the solid state NMR line shapes of these nuclei into the MHz range. Although most of this broadening can be circumvented by limiting excitations to the central -l/2 +l/2 transition? second-order effects can widen the resulting resonances and prevent the resolution of chemically inequivalent sites. In contrast to what happens in spin-'/2 spectroscopy, no single-axis spinning techniques are available for canceling the effects of these second-order anisotropies. Still, as is briefly discussed in the present Communication, bidimensional NMR methods involving multiple-quantum excitation in combination with fixed-angle sample spinning are capable of refocusing second-order quadrupolar effects and can thus be used to acquire highly resolved spectra devoid from quadrupolar, shielding, or dipolar anisotropies. Central-transition NMR experiments manage to avoid firstorder quadrupolar broadenings owing to the Hamiltonian's quadratic dependence on the S, angular momentum.2 The following term in the quadrupolee the last two, however, are anisotropic and can broaden the central transitions of powdered samples over several kHz. The effects of these anisotropies can be scaled by rapidly spinning the sample at an axis Ps3 This leads to time averaged NMR frequencies
1,196 citations
TL;DR: By use of quantitative calculations of ligand-induced chemical shift changes, it is becoming possible to determine not just the position but also the orientation of ligands, and in particular the measurement of (13)CH3 signals.
1,085 citations
TL;DR: In this article, it was shown that when these weak side-spectra are included the second moment does indeed remain invariant even though the second moments of the central portion, which is all that is observed experimentally, becomes smaller.
Abstract: HINDERED molecular rotation in solids reduces the width of their observed nuclear magnetic resonance spectra, with a consequent decrease in the measured second moments1. By contrast, on general theoretical grounds it has been shown2 that the second moments of dipolar-broadened spectra should remain invariant and should not be reduced by such motion. In a recent explanation3 of this apparent discrepancy the nuclear magnetic interaction was divided into two parts, namely, a steady mean interaction and a fluctuating part. The steady mean interaction is less than the interaction in a static crystal devoid of hindered rotation and generates an observed spectrum narrower than that of the static crystal. The fluctuating part of the interaction generates side-spectra set at integral multiples of the frequency of molecular rotation on either side of the central narrowed spectrum. Since the molecules do not rotate uniformly, but are re-oriented with an irregular motion, these side-spectra are dispersed over a band of frequencies with an intensity too weak to be observed. It was shown, however3, that when these weak side-spectra are included the second moment does indeed remain invariant even though the second moment of the central portion, which is all that is observed experimentally, becomes smaller.
1,081 citations
1,023 citations
TL;DR: In this paper, the authors have shown that the combined use of fast magic-angle spinning and bidimensional multiple-quantum (MQ) spectroscopy can refocus these anisotropies.
Abstract: Whereas solid state isotropic spectra can be obtained from spin-'/2 nuclei by fast magic-angle spinning (MAS), this methodology fails when applied on half-integer quadrupoles due to the presence of non-negligible secondorder anisotropic effects. Very recently, however, we have shown that the combined use of MAS and bidimensional multiple-quantum (MQ) spectroscopy can refocus these anisotropies; the present paper discusses theoretical and experimental aspects of this novel MQMAS methodology and illustrates its application on a series of sodium salts. It is shown that even under fixed magnetic field operation, a simple model-free inspection of the peaks in a bidimensional MQMAS NMR spectrum can separate the contributions of isotropic chemical and isotropic quadrupolar shifts for different chemical sites. Moreover the anisotropic line shapes that can be resolved from these spectra are almost unaffected by excitation distortions and can thus be used to discern the values of a site's quadrupolar coupling constant and asymmetry parameter. The conditions that maximize the MQMAS signal-to-noise ratio for a ~pin-~/z are then explored with the aid of a simple analytical model, which can also be used to explain the absence of distortions in the anisotropic line shapes. The MQMAS method thus optimized was applied to the high-resolution 23Na NMR analysis of the multi-site ionic compounds NazTeO3, Na2S03, Na3P5010, and Na2HP04; extensions of the MQMAS NMR methodology to the quantitative analysis of inequivalent sites are also discussed and demonstrated.
809 citations