Showing papers on "Solid-state nuclear magnetic resonance published in 2014"
TL;DR: This approach facilitates and accelerates the MAS NMR assignment process, shortening the spectral acquisition times and enabling the use of unsupervised state-of-the-art computational data analysis protocols originally developed for solution NMR.
Abstract: Using a set of six 1H-detected triple-resonance NMR experiments, we establish a method for sequence-specific backbone resonance assignment of magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of 5–30 kDa proteins The approach relies on perdeuteration, amide 2H/1H exchange, high magnetic fields, and high-spinning frequencies (ωr/2π ≥ 60 kHz) and yields high-quality NMR data, enabling the use of automated analysis The method is validated with five examples of proteins in different condensed states, including two microcrystalline proteins, a sedimented virus capsid, and two membrane-embedded systems In comparison to contemporary 13C/15N-based methods, this approach facilitates and accelerates the MAS NMR assignment process, shortening the spectral acquisition times and enabling the use of unsupervised state-of-the-art computational data analysis protocols originally developed for solution NMR
239 citations
TL;DR: Solid state (13)C and (1)H nuclear magnetic resonance (NMR) experiments with magic-angle spinning on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation are reported.
Abstract: We report solid state 13C and 1H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, 1H and cross-polarized 13C NMR signals from 15N,13C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T1e is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.
125 citations
TL;DR: Isotopic-labeling experimental results demonstrated that polymethylbenzenes (MBs) are intimately correlated with the formation of olefin products in the initial stage, evidencing that they work together through a paring mechanism to produce propene.
Abstract: Over zeolite H-ZSM-5, the aromatics-based hydrocarbon-pool mechanism of methanol-to-olefins (MTO) reaction was studied by GC-MS, solid-state NMR spectroscopy, and theoretical calculations. Isotopic-labeling experimental results demonstrated that polymethylbenzenes (MBs) are intimately correlated with the formation of olefin products in the initial stage. More importantly, three types of cyclopentenyl cations (1,3-dimethylcyclopentenyl, 1,2,3-trimethylcyclopentenyl, and 1,3,4-trimethylcyclopentenyl cations) and a pentamethylbenzenium ion were for the first time identified by solid-state NMR spectroscopy and DFT calculations under both co-feeding ([C-13(6)]benzene and methanol) conditions and typical MTO working (feeding [C-13]methanol alone) conditions. The comparable reactivity of the MBs (from xylene to tetramethylbenzene) and the carbocations (trimethylcyclopentenyl and pentamethylbenzium ions) in the MTO reaction was revealed by C-13-labeling experiments, evidencing that they work together through a paring mechanism to produce propene. The paring route in a full aromatics-based catalytic cycle was also supported by theoretical DFT calculations.
123 citations
TL;DR: In this paper, a single 13C-13C nuclear spin dimer near a nitrogen-vacancy centre in diamond is reported, together with a structural characterization at atomic-scale resolution.
Abstract: Being able to sense nuclear spin dimers is an important next step towards single-molecule structural analysis from NMR measurements. Now the sensing of a single 13C–13C nuclear spin dimer near a nitrogen–vacancy centre in diamond is reported, together with a structural characterization at atomic-scale resolution.
116 citations
TL;DR: Room temperature hyperpolarization achieved with DNP using photo-excited triplet electrons has potentials to be applied to a wide range of fields, including NMR spectroscopy and MRI as well as fundamental physics.
Abstract: Dynamic nuclear polarization (DNP), a means of transferring spin polarization from electrons to nuclei, can enhance the nuclear spin polarization (hence the NMR sensitivity) in bulk materials at most 660 times for 1H spins, using electron spins in thermal equilibrium as polarizing agents By using electron spins in photo-excited triplet states instead, DNP can overcome the above limit We demonstrate a 1H spin polarization of 34%, which gives an enhancement factor of 250,000 in 040 T, while maintaining a bulk sample (∼06 mg, ∼07 × 07 × 1 mm3) containing >1019 1H spins at room temperature Room temperature hyperpolarization achieved with DNP using photo-excited triplet electrons has potentials to be applied to a wide range of fields, including NMR spectroscopy and MRI as well as fundamental physics
109 citations
TL;DR: A brief overview of the quadrupolar interaction is provided, some of the basic experimental approaches used for acquiring high-resolution NMR spectra are described, and the information that these spectra can provide are discussed.
Abstract: Solid-state nuclear magnetic resonance (NMR) spectroscopy has long been established as offering unique atomic-scale and element-specific insight into the structure, disorder, and dynamics of materials. NMR spectra of quadrupolar nuclei (I > 1/2) are often perceived as being challenging to acquire and to interpret because of the presence of anisotropic broadening arising from the interaction of the electric field gradient and the nuclear electric quadrupole moment, which broadens the spectral lines, often over several megahertz. Despite the vast amount of information contained in the spectral line shapes, the problems with sensitivity and resolution have, until very recently, limited the application of NMR spectroscopy of quadrupolar nuclei in the solid state. In this Perspective, we provide a brief overview of the quadrupolar interaction, describe some of the basic experimental approaches used for acquiring high-resolution NMR spectra, and discuss the information that these spectra can provide. We then de...
106 citations
TL;DR: (15)NH4Cl in its powdered form is a suitable external reference as it produces narrow lines when compared to other reference compounds and at the same time allows for the set-up of cross-polarization NMR experiments.
103 citations
TL;DR: It is shown that recent developments in the field of dynamic nuclear polarization under magic angle spinning (MAS-DNP) could be used to dramatically increase the sensitivity of the NMR experiments, resulting in a timesaving factor of ∼625 compared to conventional solid-state NMR, which allowed the acquisition of previously infeasible data.
Abstract: Silica (SiO2) nanoparticles (NPs) were functionalized by silanization to produce a surface covered with organosiloxanes. Information about the surface coverage and the nature, if any, of organosiloxane polymerization, whether parallel or perpendicular to the surface, is highly desired. To this extent, two-dimensional homonuclear 29Si solid-state NMR could be employed. However, owing to the sensitivity limitations associated with the low natural abundance (4.7%) of 29Si and the difficulty and expense of isotopic labeling here, this technique would usually be deemed impracticable. Nevertheless, we show that recent developments in the field of dynamic nuclear polarization under magic angle spinning (MAS-DNP) could be used to dramatically increase the sensitivity of the NMR experiments, resulting in a timesaving factor of ∼625 compared to conventional solid-state NMR. This allowed the acquisition of previously infeasible data. Using both through-space and through-bond 2D 29Si–29Si correlation experiments, it ...
90 citations
TL;DR: DNP-SENS experiments can be carried on many types of uniform colloidal nanomaterials containing NMR-active nuclei, in the presence of either hydrophilic (ion-capped surfaces) or hydrophobic (capping ligands with long hydrocarbon chains) surface functionalities.
Abstract: A particularly difficult challenge in the chemistry of nanomaterials is the detailed structural and chemical analysis of multicomponent nano-objects. This is especially true for the determination of spatially resolved information. In this study, we demonstrate that dynamic nuclear polarization surface-enhanced solid-state NMR spectroscopy (DNP-SENS), which provides selective and enhanced NMR signal collection from the (near) surface regions of a sample, can be used to resolve the core-shell structure of a nanoparticle. Li-ion anode materials, monodisperse 10-20 nm large tin nanoparticles covered with a ∼3 nm thick layer of native oxides, were used in this case study. DNP-SENS selectively enhanced the weak 119Sn NMR signal of the amorphous surface SnO2 layer. Mossbauer and X-ray absorption spectroscopies identified a subsurface SnO phase and quantified the atomic fractions of both oxides. Finally, temperature-dependent X-ray diffraction measurements were used to probe the metallic β-Sn core and indicated that even after 8 months of storage at 255 K there are no signs of conversion of the metallic β-Sn core into a brittle semiconducting α-phase, a phase transition which normally occurs in bulk tin at 286 K (13 °C). Taken together, these results indicate that Sn/SnOx nanoparticles have core/shell1/shell2 structure of Sn/SnO/SnO2 phases. The study suggests that DNP-SENS experiments can be carried on many types of uniform colloidal nanomaterials containing NMR-active nuclei, in the presence of either hydrophilic (ion-capped surfaces) or hydrophobic (capping ligands with long hydrocarbon chains) surface functionalities.
88 citations
TL;DR: High-field DNP offers atomic insight into the role of molecular plasticity during the course of biomolecular function in a complex cellular environment through exploitation of the paramagnetic relaxation properties of DNP polarizing agents as direct structural probes under magic angle spinning conditions.
Abstract: Dynamic nuclear polarization (DNP) has become a powerful method to enhance spectroscopic sensitivity in the context of magnetic resonance imaging and nuclear magnetic resonance spectroscopy. We show that, compared to DNP at lower field (400 MHz/263 GHz), high field DNP (800 MHz/527 GHz) can significantly enhance spectral resolution and allows exploitation of the paramagnetic relaxation properties of DNP polarizing agents as direct structural probes under magic angle spinning conditions. Applied to a membrane-embedded K+ channel, this approach allowed us to refine the membrane-embedded channel structure and revealed conformational substates that are present during two different stages of the channel gating cycle. High-field DNP thus offers atomic insight into the role of molecular plasticity during the course of biomolecular function in a complex cellular environment.
85 citations
TL;DR: In this paper, the magic angle spinning combined with dynamic nuclear polarization (MAS-DNP) was used to enhance the sensitivity of solid-state NMR experiments and gain structural insights into this important material.
Abstract: Aluminas (Al2O3) are ubiquitous functional materials. In particular, the γ-alumina form is extensively used in research and industry as a catalyst and catalyst support. Nevertheless, a full structural description, which would aid in comprehension of its properties, is lacking and under large debate. Solid-state NMR has been used previously to study γ-alumina but is limited for certain applications, such as surface studies, due to intrinsic low sensitivity. Here, we detail the implementation of low temperature (∼100 K) magic angle spinning combined with dynamic nuclear polarization (MAS-DNP) to significantly enhance the sensitivity of solid-state NMR experiments and gain structural insights into this important material. Notably, we analyze hydrophilic and hydrophobic sample preparation protocols and their implications on the sample and resulting NMR parameters. We show that the choice of preparation does not perturb the spectrum, but it does have a large effect on NMR coherence lifetimes, as does the corre...
TL;DR: Recent progress in Magic Angle Spinning solid-state NMR spectroscopy methodologies are described, which are now available for studies of membrane protein structure determination, and a few examples, which highlight the broad capability of ssNMR Spectroscopy are outlined.
TL;DR: Solid-state NMR site-specific measurements of the dipolar order parameters and (15)N rotating frame spin-lattice (R1ρ) relaxation rates in a seven transmembrane helical protein Anabaena Sensory Rhodopsin reconstituted in lipids indicate that both the well-defined trans Membrane regions and the less structured intramembrane loops undergo restricted submicrosecond time scale motions.
Abstract: The ability to detect and characterize molecular motions represents one of the unique strengths of nuclear magnetic resonance (NMR) spectroscopy. In this study, we report solid-state NMR site-specific measurements of the dipolar order parameters and 15N rotating frame spin–lattice (R1ρ) relaxation rates in a seven transmembrane helical protein Anabaena Sensory Rhodopsin reconstituted in lipids. The magnitudes of the observed order parameters indicate that both the well-defined transmembrane regions and the less structured intramembrane loops undergo restricted submicrosecond time scale motions. In contrast, the R1ρ rates, which were measured under fast magic angle spinning conditions, vary by an order of magnitude between the TM and exposed regions and suggest the presence of intermediate time scale motions. Using a simple model, which assumes a single exponential autocorrelation function, we estimated the time scales of dominant stochastic motions to be on the order of low tens of nanoseconds for most re...
TL;DR: The role of 13C solid state nuclear magnetic resonance (ssNMR) in the elucidation of the structure of biomass and carbonaceous solids derived from biomass has been crucial since the mid-70s as discussed by the authors.
TL;DR: It is demonstrated that the application of (1)H-detected experiments at magic-angle spinning frequencies of >50 kHz enables the recording of solid-state NMR spectra suitable for quantitative analysis of protein complexes present in quantities as small as a few nanomoles.
Abstract: NMR spectroscopy is a prime technique for characterizing atomic-resolution structures and dynamics of biomolecular complexes but for such systems faces challenges of sensitivity and spectral resolution. We demonstrate that the application of 1H-detected experiments at magic-angle spinning frequencies of >50 kHz enables the recording, in a matter of minutes to hours, of solid-state NMR spectra suitable for quantitative analysis of protein complexes present in quantities as small as a few nanomoles (tens of micrograms for the observed component). This approach enables direct structure determination and quantitative dynamics measurements in domains of protein complexes with masses of hundreds of kilodaltons. Protein–protein interaction interfaces can be mapped out by comparison of the chemical shifts of proteins within solid-state complexes with those of the same constituent proteins free in solution. We employed this methodology to characterize a >300 kDa complex of GB1 with full-length human immunoglobulin...
TL;DR: In this paper, first-principles calculations using density functional theory were performed on structural models of these glasses, generated by Shell-model molecular dynamics simulations, and theoretical NMR parameters and spectra were computed using the gauge including projected augmented wave (GIPAW) method and spin-effective Hamiltonians.
TL;DR: It is demonstrated that solid-state NMR spectra of challenging nuclei with a low gyromagnetic ratio such as yttrium-89 can be acquired quickly with indirect dynamic nuclear polarization (DNP) methods.
Abstract: We demonstrate that solid-state NMR spectra of challenging nuclei with a low gyromagnetic ratio such as yttrium-89 can be acquired quickly with indirect dynamic nuclear polarization (DNP) methods. Proton to 89Y cross polarization (CP) magic angle spinning (MAS) spectra of Y3+ in a frozen aqueous solution were acquired in minutes using the AMUPol biradical as a polarizing agent. Subsequently, the detection of the 89Y and 1H NMR signals from technologically important hydrated yttrium-doped zirconate ceramics, in combination with DFT calculations, allows the local yttrium and proton environments present in these protonic conductors to be detected and assigned to different hydrogen-bonded environments.
TL;DR: Remarkable efficiency of polarization transfer can be achieved at a MAS rate of 40 kHz by both cross-polarization and INEPT, which makes these methods applicable for routine characterizations of natural abundance solids.
TL;DR: In this paper, the possibilities offered by ex situ and in situ operando 7Li solid-state nuclear magnetic resonance (NMR) are explored for the Li2Ru1-ySnyO3 family, shown previously to display cationic and anionic redox activity when used as a positive electrode for Li-ion batteries.
Abstract: The possibilities offered by ex situ and in situ operando 7Li solid-state nuclear magnetic resonance (NMR) are explored for the Li2Ru1-ySnyO3 family (0
TL;DR: How Na2O–CaO–SiO2–P2O5 compositions exhibiting an optimal bioactivity can be designed by simultaneously altering three key parameters: the silicate network connectivity, the (ortho)phosphate content, and the nNa/nCa molar ratio is defined.
Abstract: The physiological responses of silicate-based bioactive glasses (BGs) are known to depend critically on both the P content (nP) of the glass and its silicate network connectivity (NBOSi). However, while the bioactivity generally displays a nonmonotonic dependence on nP itself, recent work suggest that it is merely the net orthophosphate content that directly links to the bioactivity. We exploit molecular dynamics (MD) simulations combined with 31P and 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy to explore the quantitative relationships between NBOSi, nP, and the silicate and phosphate speciations in a series of Na2O–CaO–SiO2–P2O5 glasses spanning 2.1 ≤ NBOSi ≤ 2.9 and variable P2O5 contents up to 6.0 mol %. The fractional population of the orthophosphate groups remains independent of nP at a fixed NBOSi-value, but is reduced slightly as NBOSi increases. Nevertheless, P remains predominantly as readily released orthophosphate ions, whose content may be altered essentially independen...
TL;DR: This study shows that the use of mixing proton magnetization, instead of (15)N, via the recoupled (1)H-( 1)H dipolar couplings enable faster ( 15)N/N correlation, and demonstrates that a 3D (15]N/(15) N/(1) H experiment can render higher resolution spectra that will be useful in the structural studies of proteins at ultrafast MAS frequencies.
TL;DR: A novel zwitterionic SBA-15 type bioceramic with dual antibacterial capability has been synthesized and opens up promising expectations for the treatment of bone implant infections.
Abstract: A novel zwitterionic SBA-15 type bioceramic with dual antibacterial capability has been synthesized. The cocondensation route has been employed to functionalize SBA-15 with primary and secondary amine groups. The resulting material exhibits textural and nanostructural properties comparable to those of pure silica SBA-15, as confirmed by XRD, HR-TEM and N2 adsorption porosimetry. The presence of –NH3 4/–SiO. and >NH2 4/–SiO. zwitterionic pairs on the material surface is evidenced by FTIR and 1H / 13C CP/MAS solid state NMR. The homogeneous distribution of this zwitterionic pairs agrees with the results derived from STEM-EDS studies. z-Potential measurements indicate that the zwitterionic nature of this material is preserved at the physiological pH of 7.4. In vitro bacterial assays using S. aureus demonstrate that the zwitterionic material is capable of inhibiting 99.9% of the bacterial adhesion compared to pure silica SBA-15. Moreover, cephalexin loading and delivery assays indicate that the zwitterionic sample is capable of releasing antibiotic molecules over long time periods. This dual antibacterial capability, i.e. antibiofouling and bactericidal, opens up promising expectations for the treatment of bone implant infections.
TL;DR: In this article, the crystal structure of a powder pharmaceutical cocrystal, theophylline-nicotinamide (1':'1) crystal complex, was determined by using a combination of X-ray powder diffraction (XRPD), 1D solid state NMR, as well as density functional theory (DFT) calculations.
Abstract: The crystal structure of a powder pharmaceutical cocrystal, theophylline–nicotinamide (1 : 1) crystal complex, is determined for the first time by using a combination of X-ray powder diffraction (XRPD), 1D solid state NMR, as well as density functional theory (DFT) calculations. With the aid of solid state NMR spectroscopy, a candidate structure can be determined from XRPD data by Rietveld refinement with acceptable residual variances. The structure was subjected to periodic geometry optimization, followed by NMR parameter calculations. The agreement between experimental and computed 13C and 15N NMR chemical shift values validates the refined structure as an accurate representation of the actual cocrystal structure. Intermolecular interactions existing in the cocrystal are further confirmed by the commonly used vibrational spectra. This study confirms that the straightforward synergistic approach offers a simple and credible way to solve the crystal structure of powder cocrystal samples.
TL;DR: The results suggest that the crystal structures of GPCRs only represent a static snapshot of these highly mobile molecules, which undergo significant structural fluctuations with relatively large amplitudes in a liquid-crystalline membrane at physiological temperature.
Abstract: In spite of the recent success in crystallizing several G-protein-coupled receptors (GPCRs), a comprehensive biophysical characterization of these molecules under physiological conditions also requires the study of the molecular dynamics of these proteins. The molecular mobility of the human neuropeptide Y receptor type 2 reconstituted into dimyristoylphosphatidylcholine (DMPC) membranes was investigated by means of solid-state NMR spectroscopy. Static (15) N NMR spectra show that the receptor performs axially symmetric motions in the membrane, and several residues undergo large amplitude fluctuations. This was confirmed by quantitative measurements of the motional (1) H,(13) C order parameter of the CH, CH2 , and CH3 groups. In directly polarized (13) C NMR experiments, these order parameters showed astonishingly low values of SCH =0.55, S CH 2=0.33, and S CH 3=0.17, which corresponds to segmental amplitudes of approximately 50° in the backbone and approximately 50-60° in the side chain. At physiological temperature, (2) H NMR spectra of the deuterated receptor showed a narrow component that is indicative of molecular order parameters of S≤0.3 superimposed with a very broad spectrum that could stem from the transmembrane α-helices. These results suggest that the crystal structures of GPCRs only represent a static snapshot of these highly mobile molecules, which undergo significant structural fluctuations with relatively large amplitudes in a liquid-crystalline membrane at physiological temperature.
TL;DR: It is found that the microphase separation is enhanced by the increase of temperature as well as the incorporation of cross-linkers, and proton T2 relaxometry combined with multiple-quantum NMR is a powerful method to study the heterogeneous structures and dynamics of a multiphase polymer system.
Abstract: Polyurethane material is widely utilized in industry and daily life due to its versatile chemistry and relatively easy handling Here, we focused on a novel thermally reversible cross-linked polyur
TL;DR: In this paper, a series of HCl salts of active pharmaceutical ingredients (APIs) have been characterized via 35Cl solid-state NMR (SSNMR) spectroscopy and first-principles plane-wave density functional theory (DFT) calculations of 35Cl NMR interaction tensors.
Abstract: A series of HCl salts of active pharmaceutical ingredients (APIs) have been characterized via35Cl solid-state NMR (SSNMR) spectroscopy and first-principles plane-wave density functional theory (DFT) calculations of 35Cl NMR interaction tensors. 35Cl NMR spectra have been acquired at both standard (9.4 T) and high (21.1 T) magnetic field strengths, on stationary samples and under conditions of magic-angle spinning (MAS). The 35Cl electric field gradient (EFG) and chemical shift (CS) tensor parameters are readily extracted from analytical simulations of these spectra. These parameters are distinct for each sample, indicating that these spectra can be used as fingerprints for identifying unique solid phases. It is possible to correlate the 35Cl EFG parameters (the quadrupolar coupling constant, CQ, and the asymmetry parameter, ηQ) to the hydrogen-bonding environments of each chlorine anion, and several simple trends are observed. 35Cl EFG tensors obtained from plane-wave DFT calculations are found to be in good agreement with experiment, and unique structural insights are gained by considering the predicted EFG tensor orientations and the signs of the quadrupolar coupling constants. 35Cl SSNMR can be easily applied for the differentiation of polymorphs of HCl APIs, since the spectra are sensitive to even the subtlest changes in the chlorine anion environments. We discuss the application of this combination of techniques as both standalone and complementary NMR crystallography methodologies for structural characterization and potential high-throughput screening of polymorphs of HCl APIs.
TL;DR: In this article, the changes caused by heat treatment of gibbsite powder at 300-1473 K were studied using the X-ray diffraction (XRD), Xray photoemission (XPS) spectra and 27 Al magic angle spinning nuclear magnetic resonance spectroscopy (27 Al MAS NMR).
TL;DR: This manuscript shows that the incorporation of a phase modulation into a long quadrupolar recoupling pulse, lasting 10 rotor periods that are sandwiched between rotor-synchronized pairs of dipolar Recoupling π pulses, extends significantly the range of the values of the quadrupole moments that can be accessed by the experiment.
TL;DR: In this article, the acid properties of a dehydrated borosilicate, HAMS-1B (H-[B]-ZSM-5), including acid types, strengths, location, and quantities are investigated by means of trialkylphosphine oxides through multinuclear 1D/2D MAS NMR experiments.
TL;DR: Phase-Alternating R-Symmetry dipolar recoupling scheme (PARS) permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons.
Abstract: We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear 1H-X (X = 13C, 15N, 31P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the 1H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the 1H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from 1H chemical shift anisotropy, while keeping the 1H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [15N]-N-acetyl-valine and [U-13C,15N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate 1H-15N dipolar couplings in the context of 3D experiments is presented on U-13C,15N-enriched dynein light chain protein LC8.