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Techniques for enhancing the signals arising from low-γ, insensitive (I) nuclei are central to solid-state nuclear magnetic resonance. One of the leading and best-established methods to sensitize these unreceptive species is Hartmann–Hahn cross polarization (HH-CP), a polarization transfer mechanism often executed under MAS. Herein, we explore the possibility of utilizing the 1H dipolar order created via adiabatic demagnetization in the rotating frame (ADRF), to enhance the unreceptive spins under MAS. It is found that an efficient polarization transfer via ADRF-CPMAS is not only possible but can exceed, at least in some instances involving plastic crystals, the efficiency of an optimized HH-CPMAS transfer. The experiment requires low radiofrequency nutation fields on both the 1H- and the I-spin channels, and displays unusual matching conditions that are reminiscent of the zero- and double-quantum matching conditions arising under CPMAS, albeit centered at zero frequency and demanding the simultaneous involvement of several spins. The origin of these multi-spin transfer processes is analytically derived and numerically simulated in predictions that compare well with experimental 13C and 15N results collected on model compounds at different spinning speeds. These derivations start from descriptions that depart from traditional thermodynamic arguments, and treat instead the ADRF processes in static and spinning solids on the basis of coherent evolutions. The predictions of these analytical derivations are corroborated by numerical simulations. The effects of additional factors, including chemical shift anisotropies, J-couplings, and radiofrequency inhomogeneities, are also theoretically and experimentally explored. [ABSTRACT FROM AUTHOR]

The structure of zinc aluminosilicate glasses with the composition (ZnO)x(Al2O3)y(SiO2)1−x−y, where 0 ≤ x < 1, 0 ≤ y < 1, and x + y < 1, was investigated over a wide composition range by combining neutron and high-energy x-ray diffraction with 27Al magic angle spinning nuclear magnetic resonance spectroscopy. The results were interpreted using an analytical model for the composition-dependent structure in which the zinc ions do not act as network formers. Four-coordinated aluminum atoms were found to be in the majority for all the investigated glasses, with five-coordinated aluminum atoms as the main minority species. Mean Al–O bond distances of 1.764(5) and 1.855(5) Å were obtained for the four- and five-coordinated aluminum atoms, respectively. The coordination environment of zinc was not observed to be invariant. Instead, it is dependent on whether zinc plays a predominantly network-modifying or charge-compensating role and, therefore, varies systematically with the glass composition. The Zn–O coordination number and bond distance were found to be 4.36(9) and 2.00(1) Å, respectively, for the network-modifying role vs 5.96(10) and 2.08(1) Å, respectively, for the charge-compensating role. The more open coordination environment of the charge-compensator is related to an enhanced probability of zinc finding bridging oxygen atoms as nearest-neighbors, reflecting a change in the connectivity of the glass network comprising four-coordinated silicon and aluminum atoms as the alumina content is increased. [ABSTRACT FROM AUTHOR]

Solid-state nuclear spin diffusion is the coherent and reversible process through which spin order is transferred via dipolar couplings. With the recent increases in magic-angle spinning (MAS) frequencies and magnetic fields becoming routinely applied in solid-state nuclear magnetic resonance, understanding how the increased 1H resolution obtained affects spin diffusion is necessary for interpretation of several common experiments. To investigate the coherent contributions to spin diffusion with fast MAS, we have developed a low-order correlation in Liouville space model based on the work of Dumez et al. (J. Chem. Phys. 33, 224501, 2010). Specifically, we introduce a new method for basis set selection, which accounts for the resonance-offset dependence at fast MAS. Furthermore, we consider the necessity of including chemical shift, both isotropic and anisotropic, in the modeling of spin diffusion. Using this model, we explore how different experimental factors change the nature of spin diffusion. Then, we show case studies to exemplify the issues that arise in using spin diffusion techniques at fast spinning. We show that the efficiency of polarization transfer via spin diffusion occurring within a deuterated and 100% back-exchanged protein sample at 60 kHz MAS is almost entirely dependent on resonance offset. We additionally identify temperature-dependent magnetization transfer in beta-aspartyl L-alanine, which could be explained by the influence of an incoherent relaxation-based nuclear Overhauser effect. [ABSTRACT FROM AUTHOR]

A new heteronuclear decoupling sequence for solid-state NMR and magic angle spinning faster than 60 kHz was recently introduced [Simion et al., J. Chem. Phys. 157, 014202 (2022)]. It was dubbed ROtor-Synchronized Phase-Alternated Cycles (ROSPAC), and it offers robustness for a large range of chemical shifts and low radio-frequency (RF) powers and is almost independent of the radio-frequency power. Here, we theoretically explore the robustness of the ROSPAC sequence toward 1H offset and RF field inhomogeneities, as well as the spacing effect of the π pulses on the decoupling efficiency. We use a generalized theoretical framework based on the Floquet theory to assess these parameters. The optimum decoupling conditions, where the magnitude of the second-order cross-terms and first-order resonance conditions are small, were identified. [ABSTRACT FROM AUTHOR]

Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 (LATP) NASICON-type ceramic, due to its high bulk conductivity, is believed to be one of the most appropriate material for application as solid electrolyte in all-solid-state lithium-ion batteries. However, its highly resistant grain boundaries strongly limit the total ionic conductivity. Therefore, in this work, an attempt has been made to overcome this problem by introducing a Li-ion conducting additive LiAlSiO 4 (LASO) to LATP base matrix in order to provide more conduction paths for lithium ions between grains. The properties of Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 –xLiAlSiO 4 (0.02 ≤ x ≤ 0.1) composite system were studied by means of: high-temperature X-ray powder diffractometry (HTXRD), 6Li, 27Al, and 31P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), scanning electron microscopy (SEM), and impedance spectroscopy (IS) methods. The obtained ceramic LATP–LASO materials exhibited high values of bulk conductivity, above 10−3 S/cm, and good total conductivity, exceeding 10−4 S/cm. The factors responsible for the enhancement, but also for the deterioration of total conductivity, i.e. microstructure and grain boundaries, are identified and discussed in this work. [ABSTRACT FROM AUTHOR]

Known for their high stability and surfactant properties, per‐ and polyfluoroalkyl substances (PFAS) have been widely used in a range of manufactured products. Despite being largely phased out due to concerns regarding their persistence, bioaccumulation, and toxicity, legacy PFAS such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid continue to persist at high levels in the environment, posing risks to aquatic organisms. We used high‐resolution magic angle spinning nuclear magnetic resonance spectroscopy in intact zebrafish (Danio rerio) embryos to investigate the metabolic pathways altered by PFOS both before and after hatching (i.e., 24 and 72 h post fertilization [hpf], respectively). Assessment of embryotoxicity found embryo lethality in the parts‐per‐million range with no significant difference in mortality between the 24‐ and 72‐hpf exposure groups. Metabolic profiling revealed mostly consistent changes between the two exposure groups, with altered metabolites generally associated with oxidative stress, lipid metabolism, energy production, and mitochondrial function, as well as specific targeting of the liver and central nervous system as key systems. These metabolic changes were further supported by analyses of tissue‐specific production of reactive oxygen species, as well as nontargeted mass spectrometric lipid profiling. Our findings suggest that PFOS‐induced metabolic changes in zebrafish embryos may be mediated through previously described interactions with regulatory and transcription factors leading to disruption of mitochondrial function and energy metabolism. The present study proposes a systems‐level model of PFOS toxicity in early life stages of zebrafish, and also identifies potential biomarkers of effect and exposure for improved environmental biomonitoring. Environ Toxicol Chem 2024;43:896–914. © 2024 SETAC [ABSTRACT FROM AUTHOR]

Infrared (IR) transparent materials with longer optical window and higher mechanical properties are highly demanded in optical communication, IR imaging, sensing and laser optics. Although transparent ceramics have higher mechanical strength, their production is still difficult using conventional sintering techniques. Herein, new IR transparent CaO–Ta 2 O 5 –Al 2 O 3 glass-ceramics (TGCs) containing cubic ɑ-CaTa 2 O 6 nanocrystals are reported. They exhibit a broadband transmitting window (0.5–5.5 μm) with high IR transmittance (∼80 %) and high refractive indices (n d = 1.96, n 1530 = 1.93). The effects of heat treatment holding time on the structure and properties of TGCs are investigated. A slightly increased proportion of crystalline phase is determined by Rietveld refinement. 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy reveals that partial Al[4] and almost all Al[5] in the precursor glass are converted to Al[6] in the residual glass after crystallization. CaTa 2 O 6 nanocrystals with amorphous shells are present within the nanodroplet domains, and a significant Ta enrichment is clearly observed. A confined crystallization process is proposed to understand the heat treatment time dependent structural characteristics and mechanical properties of the obtained TGCs. Vickers hardness (H V) of 12.01 GPa and Young's modulus (E) of 248.8 GPa are achieved in TGCs, making them promising candidates as high-performance IR materials for optical applications. [ABSTRACT FROM AUTHOR]

We have designed a noble metal-free porous organic polymer (TDA-Trz-POP) having N- and S-rich surface and it showed very low overpotential (129.2 mV w.r.t RHE for 10 mA cm−2 current density) and low Tafel slope (82.1 mV/deg) in the electrochemical water splitting. [Display omitted] Water splitting is a long-standing quest to material research for mitigating the global energy crisis. Despite high efficiency shown by several high cost noble metal containing electrocatalysts in the water splitting reaction, scientists are focused on alternate metal-free carbon or polymer based materials with comparable activity to make the process economical. In this article, we have strategically designed a noble metal-free thiadiazole (TDA) and triazine (Trz) linked porous organic polymer (TDA-Trz-POP) having N- and S-rich surface. Powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), solid state 13C magic angle spinning nuclear magnetic resonance (MAS-NMR) and X-ray photoelectron spectroscopic (XPS) analyses have been performed to predict its probable framework structure. This scrunch paper type TDA-Trz-POP shows an extravagant potential for the hydrogen evolution reaction (HER) with a low overpotential (129.2 mV w.r.t. RHE for 10 mA cm−2 current density) and low Tafel slope (82.1 mV deg−1). Again, this metal-free catalyst shows oxygen evolution reaction (OER) at 410 mV overpotential w.r.t RHE for 10 mA cm−2 current density with a lower Tafel slope of 104.5 mV deg−1. This bifunctional activity was further tested in two electrodes set-up under different pH conditions. The porosity seems to be a blessing in the electrocatalytic performance of this metal-free electrocatalyst material. Further, the mystery behind the activity of both HER and OER has been resolved through the density functional theory (DFT) analysis. This work provides an insight to the material scientists for low cost, metal-free material design for the efficient water splitting reaction. [ABSTRACT FROM AUTHOR]

Photosynthetic reaction centers (RCs) are membrane proteins converting photonic excitations into electric gradients. The heliobacterial RCs (HbRCs) are assumed to be the precursors of all known RCs, making them a compelling subject for investigating structural and functional relationships. A comprehensive picture of the electronic structure of the HbRCs is still missing. In this work, the combination of selective isotope labelling of 13C and 15N nuclei and the utilization of photo-CIDNP MAS NMR (photochemically induced dynamic nuclear polarization magic-angle spinning nuclear magnetic resonance) allows for highly enhanced signals from the radical-pair-forming cofactors. The remarkable magnetic-field dependence of the solid-state photo-CIDNP effect allows for observation of positive signals of the electron donor cofactor at 4.7 T, which is interpreted in terms of a dominant contribution of the differential relaxation (DR) mechanism. Conversely, at 9.4 T, the emissive signals mainly originate from the electron acceptor, due to the strong activation of the three-spin mixing (TSM) mechanism. Consequently, we have utilized two-dimensional homonuclear photo-CIDNP MAS NMR at both 4.7 T and 9.4 T. These findings from experimental investigations are corroborated by calculations based on density functional theory (DFT). This allows us to present a comprehensive investigation of the electronic structure of the cofactors involved in electron transfer (ET). [ABSTRACT FROM AUTHOR]

Lithium salts continue to find pharmaceutical applications, particularly as psychiatric medications. As with any active pharmaceutical ingredient, structural polymorphism is an important concern for lithium-based medications that can influence solubility and other physicochemical properties. Here we report a 13C, 1H, and 7Li magic-angle spinning solid-state nuclear magnetic resonance (MAS SSNMR) study of two 1:1 polymorphic ionic cocrystals of lithium 4-methoxybenzoate and L-proline (L4MPRO(α) and L4MPRO(β)). One-dimensional 13C cross-polarization MAS and two-dimensional heteronuclear correlation NMR spectra hint at differential mobilities of the proline and benzoate moieties for the two polymorphs. Five key resonances differ in 13C chemical shift by more than 1 ppm between the two polymorphs, clearly distinguishing between them. Gauge-including projector-augmented-wave density functional theory calculations of 13C and 1H magnetic shielding constants correlate strongly with the experimental chemical shifts for both polymorphs. R2 and root-mean-square deviation metrics are shown to be insufficient in the case of 13C, but sufficient in the case of 1H, for differentiating between the polymorphs. 7Li satellite-transition MAS NMR of both polymorphs are identical, as are the computed lithium magnetic shielding constants, demonstrating the insensitivity of 7Li NMR to polymorphism in these samples. This work highlights the utility of solid-state NMR spectroscopy for examining ionic salt cocrystals and also highlights some caveats in this regard. [ABSTRACT FROM AUTHOR]

A proper functioning placenta is essential for normal fetal development. The placenta has a vital function as a protective barrier and is critical for nutrient and waste exchange for the developing fetus. Our group and others have reported sex differences in both placental structure and function; however, differences in the placental metabolome between female and male fetuses have been understudied. Here, placental tissue samples were collected from healthy pregnant CD-1 mice in late gestation (n = 26 female and n = 27 male placentas from 17 dams at embryonic day 17.5). Metabolite profiles were determined using 1H magic angle spinning nuclear magnetic resonance. The relative concentration of alanine was significantly higher in male placentas whereas, threonine was higher in female placentas (p < 0.05). This study adds to the growing literature demonstrating sex differences in healthy placental function and emphasizes the importance of examining both female and male placentas in metabolomics studies. [ABSTRACT FROM AUTHOR]

This paper reports the principal values of the 13C chemical shift tensors for five nitrogen‐dense compounds (i.e., cytosine, uracil, imidazole, guanidine hydrochloride, and aminoguanidine hydrochloride). Although these are all fundamentally important compounds, the majority do not have 13C chemical shift tensors reported in the literature. The chemical shift tensors are obtained from 1H→13C cross‐polarization magic‐angle spinning (CP/MAS) experiments that were conducted at a high field of 18.8 T to suppress the effects of 14N‐13C residual dipolar coupling. Quantum chemical calculations using density functional theory are used to obtain the 13C magnetic shielding tensors for these compounds. The best agreement with experiment arises from calculations using the hybrid functional PBE0 or the double‐hybrid functional PBE0‐DH, along with the triple‐zeta basis sets TZ2P or pc‐3, respectively, and intermolecular effects modeled using large clusters of molecules with electrostatic embedding through the COSMO approach. These measurements are part of an ongoing effort to expand the catalog of accurate 13C chemical shift tensor measurements, with the aim of creating a database that may be useful for benchmarking the accuracy of quantum chemical calculations, developing nuclear magnetic resonance (NMR) crystallography protocols, or aiding in applications involving machine learning or data mining. This work was conducted at the National High Magnetic Field Laboratory as part of a 2‐week school for introducing undergraduate students to practical laboratory experience that will prepare them for scientific careers or postgraduate studies. [ABSTRACT FROM AUTHOR]

Solid state NMR is widely used to study the orientation and other structural features of proteins and peptides in lipid bilayers. Using data obtained by PISEMA (Polarization Inversion Spin Exchange at Magic Angle) experiments, periodic spectral patterns arise from well‐aligned α‐helical molecules. Significant problems in the interpretation of PISEMA spectra may arise for systems that do not form perfectly defined secondary structures, like α‐helices, or the signal pattern is disturbed by molecular motion. Here, we present a new method that combines molecular dynamics simulation with tensorial orientational constraints (MDOC) and chemical shift tensor calculations for the simulation and interpretation of PISEMA‐like spectra. The calculations include the spectra arising from non α‐helical molecules and molecules with non‐uniform intrinsic mobility. In a first step, dipolar or quadrupolar interaction tensors drive molecular rotations and reorientations to obtain the proper mean values as observed in corresponding NMR experiments. In a second step, the coordinate snapshots of the MDOC simulations are geometry optimized with the isotropic 15N chemical shifts as constraints using Bond Polarization Theory (BPT) to provide reliable 15N CS tensor data. The averaged dipolar 1H‐15N couplings and the δzz tensor components can then be combined to simulate PISEMA patterns. We apply this method to the ß‐helical peptide gramicidin A (gA) and demonstrate that this method enables the assignment of most PISEMA resonances. In addition, MDOC simulations provide local order parameters for the calculated sites. These local order parameters reveal large differences in backbone mobility between L‐ and D‐amino acids of gA. [ABSTRACT FROM AUTHOR]

In this study, the changes in the phase and microstructure of alkali-activated slag (AAS) in ultralow-temperature environments (−170°C) was experimentally studied by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric (TG), scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS), Si29 magic-angle spinning nuclear magnetic resonance (MAS NMR), and pore structure. The results show that as the modulus of water glass increased, the mass loss of AAS after the ultralow-temperature freeze–thaw cycles (ULT-FTC) decreased, the freeze–thaw resistance increased. The ULT-FTC caused the internal structure of the AAS samples using different activators to slip and rearrange. Partial calcium-(alumina)-silicate-hydrate gel [C─ (A)─ S─ H] gel was decalcified. The gel structure formed using 2.0 M water glass as the activator was the most stable. The dense structure with a lower Ca/Si ratio enables the AAS to maintain a relatively stable microstructure after undergoing ULT-FTC. [ABSTRACT FROM AUTHOR]

Saturation of electron magnetization by microwave irradiation under magic-angle spinning (MAS) is studied theoretically. The saturation is essential for dynamic nuclear polarization (DNP) enhancement of nuclear magnetic resonance signals. For a spin with a large g-anisotropy and a long T1 relative to the rotor period, the sample rotation distributes saturation to the whole powder sample spectrum. Analytical expressions for the saturation and frequency profiles are obtained. For a pair of coupled electrons such as those in bis-nitroxides, which are commonly used for MAS DNP, an el–er model (where el and er stand for electrons on the left and the right, respectively, in their spectral positions) is introduced to simplify the analysis of a coupled two-spin system under MAS. For such a system, strong electron couplings exchange magnetization during dipolar/J rotor events when the two electron frequencies cross each other. The exchange is equivalent to a swap of the el and er electrons. This allows for the treatment of a coupled spin pair as two independent spins such that an analytical solution can be obtained for the steady-state magnetization and the difference between the two electrons. The theoretical study with its analytical result provides a simple physical picture of electron saturation under MAS and of how radical properties and experimental parameters affect cross-effect DNP. The effects of depolarization and the extension to more coupled electron spins are also discussed using this approach. [ABSTRACT FROM AUTHOR]

Neutron diffraction with magnesium isotope substitution, high energy x-ray diffraction, and 29Si, 27Al, and 25Mg solid-state nuclear magnetic resonance (NMR) spectroscopy were used to measure the structure of glassy diopside (CaMgSi2O6), enstatite (MgSiO3), and four (MgO)x(Al2O3)y(SiO2)1−x−y glasses, with x = 0.375 or 0.25 along the 50 mol. % silica tie-line (1 − x − y = 0.5) or with x = 0.3 or 0.2 along the 60 mol. % silica tie-line (1 − x − y = 0.6). The bound coherent neutron scattering length of the isotope 25Mg was remeasured, and the value of 3.720(12) fm was obtained from a Rietveld refinement of the powder diffraction patterns measured for crystalline 25MgO. The diffraction results for the glasses show a broad asymmetric distribution of Mg–O nearest-neighbors with a coordination number of 4.40(4) and 4.46(4) for the diopside and enstatite glasses, respectively. As magnesia is replaced by alumina along a tie-line with 50 or 60 mol. % silica, the Mg–O coordination number increases with the weighted bond distance as less Mg2+ ions adopt a network-modifying role and more of these ions adopt a predominantly charge-compensating role. 25Mg magic angle spinning (MAS) NMR results could not resolve the different coordination environments of Mg2+ under the employed field strength (14.1 T) and spinning rate (20 kHz). The results emphasize the power of neutron diffraction with isotope substitution to provide unambiguous site-specific information on the coordination environment of magnesium in disordered materials. [ABSTRACT FROM AUTHOR]

This document contains abstracts from the Annual Meeting of the German Society of Skeletal Radiology (DGMSR) in 2024. The abstracts cover a range of topics in radiology research. One study compared routine CT scans with dedicated quantitative CT scans for assessing osteoporosis and fracture risk, finding that routine CT performed as well as QCT. Another study evaluated a deep learning-based FLAIR sequence for diagnosing inflammatory knee synovitis and found it to be equivalent to contrast-enhanced T1-weighted imaging. A third study explored the use of deep learning-based image reconstruction in accelerated turbo-spin-echo MRI of the knee at 7 Tesla, which improved image quality and reduced acquisition time. The fourth study investigated data augmentation strategies to improve AI models in analyzing torsional alignment. The final abstract examined the frequency of combined femoral and tibial torsional malalignment in symptomatic patients with patellar instability. Other studies in the document covered topics such as deltoid muscle fatty infiltration and shoulder function after reverse shoulder arthroplasty, diagnostic efficacy of MRI and low-dose CT in axial spondyloarthritis, and combining compressed sensing and deep learning for accelerated 3D-MRI sequences of the knee. Additionally, there were studies on quantifying tendon degeneration, radiopalmar ganglion cysts, and a versatile turbo spin echo platform for MRI of the knee joint. [Extracted from the article]

Coupled pairs of spin-1/2 nuclei support one singlet state and three triplet states. In many circumstances, the nuclear singlet order, defined as the difference between the singlet population and the mean of the triplet populations, is a long-lived state that persists for a relatively long time in solution. Various methods have been proposed for generating singlet order, starting from nuclear magnetization. This requires the stimulation of singlet-to-triplet transitions by modulated radiofrequency fields. We show that a recently described pulse sequence, known as PulsePol [Schwartz et al., Sci. Adv., 4, eaat8978 (2018)], is an efficient technique for converting magnetization into long-lived singlet order. We show that the operation of this pulse sequence may be understood by adapting the theory of symmetry-based recoupling sequences in magic-angle-spinning solid-state nuclear magnetic resonance (NMR). The concept of riffling allows PulsePol to be interpreted by using the theory of symmetry-based pulse sequences and explains its robustness. This theory is used to derive a range of new pulse sequences for performing singlet–triplet excitation and conversion in solution NMR. Schemes for further enhancing the robustness of the transformations are demonstrated. [ABSTRACT FROM AUTHOR]

Dynamic processes in molecules can occur on a large range of time scales, and it is important to understand which time scales of motion contribute to different parameters used in dynamics measurements. For spin relaxation, this can easily be understood from the sampling of the spectral-density function by different relaxation-rate constants. In addition to data from relaxation measurements, determining dynamically-averaged anisotropic interactions in magic-angle spinning (MAS) solid-state NMR allows better quantification of the amplitude of molecular motion. For partially averaged anisotropic interactions, the relevant time scales of motion are not so clearly defined and whether the averaging depends on the experimental methods (e.g., pulse sequences) or conditions (e.g., MAS frequency, magnitude of anisotropic interaction, rf-field amplitudes) is not fully understood. To investigate these questions, we performed numerical simulations of dynamic systems based on the stochastic Liouville equation using several experiments for recoupling the dipolar-coupling, CSA or quadrupolar coupling. The transition between slow motion, where parameters characterizing the anisotropic interaction are not averaged, and fast motion, where the tensors are averaged leading to a scaled anisotropic quantity, occurs over a window of motional rate constants that depends mainly on the strength of the interaction. This transition region can span two orders of magnitude in exchange-rate constants (typically in the μs range) but depends only marginally on the employed recoupling scheme or sample spinning frequency. Residual couplings in off-magic-angle experiments, however, average over longer time scales of motion. While in principle one may gain information on the time scales of motion from the transition area, extracting such information is hampered by low signal-to-noise ratio in experimental spectra due to fast relaxation that occurs in the same region. [ABSTRACT FROM AUTHOR]

Calcium borate glass is a challenging system, due to the rich variety of borate units and alterable boron coordination number, and hence they are also of particular interest for academic study. In this study, neutron diffraction, solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) and Raman spectroscopy were combined with first-principles calculations, experience potential structure refinement (EPSR) simulations to investigate the structure of x CaO·(1- x)11B 2 O 3 glass. Property data such as density and glass transition temperature were also measured to study the impact of structural changes on the properties of glasses. The structure of calcium borate glass was analyzed using various methods including structural unit, atomic pair bond length, coordination number, ring structure, chain structure and cavity distribution. Most notably, the atomic labeling method plays a key role in the structural analysis process. Through this method some new conclusions were obtained. For example, the increase of CaO content mainly leads to the conversion of BO to NBO in the glass structure, and has little effect on the content of BO 3 and BØ 4 -. This result further leads to an increase in Ca-NBO interactions. Interestingly, the bond length distribution of Ca-NBO and B-NBO is shorter than that of Ca-BO and B-BO, so the glass structure becomes denser. The structural reason why the density of calcium borate glass is less than the crystal density was also revealed. This study contributes to unveiling the structure of calcium borate glass and exploring the correlation between the structure and properties of calcium borate glass, which provides a valuable reference for developing more valuable amorphous materials. [ABSTRACT FROM AUTHOR]

The arbovirus Chikungunya (CHIKV) is transmitted by Aedes mosquitoes in urban environments, and in humans, it triggers debilitating symptoms involving long-term complications, including arthritis and Guillain-Barré syndrome. The development of antiviral therapies is relevant, as no efficacious vaccine or drug has yet been approved for clinical application. As a detailed map of molecules underlying the viral infection can be obtained from the metabolome, we validated the metabolic signatures of Vero E6 cells prior to infection (CC), following CHIKV infection (CV) and also upon the inclusion of the nsP2 protease inhibitor wedelolactone (CWV), a coumestan which inhibits viral replication processes. The metabolome groups evidenced significant changes in the levels of lactate, myo-inositol, phosphocholine, glucose, betaine and a few specific amino acids. This study forms a preliminary basis for identifying metabolites through HR-MAS NMR (High Resolution Magic Angle Spinning Nuclear Magnetic Ressonance Spectroscopy) and proposing the affected metabolic pathways of cells following viral infection and upon incorporation of putative antiviral molecules. [ABSTRACT FROM AUTHOR]

Separation and reuse of the catalytically active metal complexes are persistent issues in homogeneous catalysis. Supported Ionic Liquid Phase (SILP) catalysts, where the catalytic center is dissolved in a thin film of a stable ionic liquid, deposited on a solid support, present a promising alternative. However, the dissolution of the metal center in the film leaves little control over its position and its activity. We present here four novel, task‐specific ionic liquids [FPhnImHR]I (n=1, 2; R=PEG2, C12H25), designed to self‐assemble on a silica surface without any covalent bonding and offering a metal binding site in a controlled distance to the support. Advanced multinuclear solid‐state NMR spectroscopic techniques under Magic Angle Spinning, complemented by molecular dynamics (MD) simulations, allow us to determine their molecular conformation when deposited inside SBA‐15 as a model silica support. We provide here conceptual proof for a rational design of ionic liquids self‐assembling into thin films, opening an avenue for a second, improved generation of SILP catalysts. [ABSTRACT FROM AUTHOR]

The possible internal dynamics of non‐isotope‐labeled small‐molecule ligands inside a target protein is inherently difficult to capture. Whereas high crystallographic temperature factors can denote either static disorder or motion, even moieties with very low B‐factors can be subject to vivid motion between symmetry‐related sites. Here we report the experimental identification of internal μs timescale dynamics of a high‐affinity, natural‐abundance ligand tightly bound to the enzyme human carbonic anhydrase II (hCAII) even within a crystalline lattice. The rotamer jumps of the ligand's benzene group manifest themselves both, in solution and fast magic‐angle spinning solid‐state NMR 1H R1ρ relaxation dispersion, for which we obtain further mechanistic insights from molecular‐dynamics (MD) simulations. The experimental confirmation of rotameric jumps in bound ligands within proteins in solution or the crystalline state may improve understanding of host‐guest interactions in biology and supra‐molecular chemistry and may facilitate medicinal chemistry for future drug campaigns. [ABSTRACT FROM AUTHOR]

Skutterudites are of high interest in current research due to their diversity of structures comprising empty, partially filled and filled variants, mostly based on metallic compounds. We herein present Ba12[BN2]6.67H4, forming a non‐metallic filled anti‐skutterudite. It is accessed in a solid‐state ampoule reaction from barium subnitride, boron nitride and barium hydride at 750 °C. Single‐crystal X‐ray and neutron powder diffraction data allowed to elucidate the structure in the cubic space group Im3‾ ${\bar{3}}$ (no. 204). The barium and hydride atoms form a three‐dimensional network consisting of corner‐sharing HBa6 octahedra and Ba12 icosahedra. Slightly bent [BN2]3− units are located in the icosahedra and the voids in‐between. 1H and 11B magic angle spinning (MAS) NMR experiments and vibrational spectroscopy further support the structure model. Quantum chemical calculations coincide well with experimental results and provide information about the electronic structure of Ba12[BN2]6.67H4. [ABSTRACT FROM AUTHOR]

Amide-proton detected magic-angle spinning NMR of deuterated proteins has become a main technique in NMR-based structural biology. In standard deuteration protocols that rely on D2O-based culture media, non-exchangeable amide sites remain deuterated, making these sites unobservable. Here we demonstrate that proteins produced with H2O-based culture medium doped with deuterated cell lysate allow to overcome this 'reprotonation bottleneck', while retaining a high level of deuteration (ca. 80 %) and narrow line widths. We quantified coherence life times of several proteins prepared with this labelling pattern over a range of MAS frequencies (40–100 kHz). We demonstrate that under commonly used conditions (50–60 kHz MAS), amide 1H line widths with our labelling approach are comparable to those of perdeuterated proteins and better than those of protonated samples at 100 kHz. For three proteins in the 33–50 kDa size range many previously unobserved amides become visible. We report how to prepare the deuterated cell lysate for our approach from fractions of perdeuterated cultures which are usually discarded, and show that such media can be used identically to commercial media. The residual protonation of Hα sites allows for well-resolved Hα-detected spectra and Hα resonance assignment, exemplified by the de novo assignment of 168 Hα sites in a 39 kDa protein. The approach based on this H2O/cell-lysate deuteration and MAS frequencies compatible with 1.3 or 1.9 mm rotors presents a strong sensitivity benefit over 0.7 mm/100 kHz MAS experiments. [ABSTRACT FROM AUTHOR]

Water is a ubiquitous component in heterogeneous catalysis over zeolites and can significantly influence the catalyst performance. However, the detailed mechanism insights into zeolite‐catalyzed reactions under microscale aqueous environment remain elusive. Here, using multiple dimensional solid‐state NMR experiments coupled with ultrahigh magic angle spinning technique and theoretical simulations, we establish a fundamental understanding of the role of water in benzene methylation over ZSM‐5 zeolite under water vapor conditions. We show that water competes with benzene for the active sites of zeolite and facilitates the bimolecular reaction mechanism. The growth of water clusters induces a micro‐hydrophobic effect in zeolite pores, which reorients benzene molecules and drives their interactions with surface methoxy species (SMS) on zeolite. We identify the formation and evolution of active SMS‐Benzene complexes in a microscale aqueous environment and demonstrate that their accumulation in zeolite pores boosts benzene conversion and methylation. [ABSTRACT FROM AUTHOR]

Amide-proton-detected magic-angle-spinning NMR of deuterated proteins has become a main technique in NMR-based structural biology. In standard deuteration protocols that rely on D 2 O-based culture media, non-exchangeable amide sites remain deuterated, making these sites unobservable. Here we demonstrate that proteins produced with a H 2 O-based culture medium doped with deuterated cell lysate allow scientists to overcome this "reprotonation bottleneck" while retaining a high level of deuteration (ca. 80 %) and narrow linewidths. We quantified coherence lifetimes of several proteins prepared with this labeling pattern over a range of magic-angle-spinning (MAS) frequencies (40–100 kHz). We demonstrate that under commonly used conditions (50–60 kHz MAS), the amide 1 H linewidths with our labeling approach are comparable to those of perdeuterated proteins and better than those of protonated samples at 100 kHz. For three proteins in the 33–50 kDa size range, many previously unobserved amides become visible. We report how to prepare the deuterated cell lysate for our approach from fractions of perdeuterated cultures which are usually discarded, and we show that such media can be used identically to commercial media. The residual protonation of H α sites allows for well-resolved H α -detected spectra and H α resonance assignment, exemplified by the de novo assignment of 168 H α sites in a 39 kDa protein. The approach based on this H 2 O/cell-lysate deuteration and MAS frequencies compatible with 1.3 or 1.9 mm rotors presents a strong sensitivity benefit over 0.7 mm 100 kHz MAS experiments. [ABSTRACT FROM AUTHOR]

Agricultural management practices play a significant role in regulating the potential for soil organic carbon (SOC) sequestration. The objective of this study was to determine the effects of cropping systems and tillage practices on the chemistry and thermal stability of topsoil SOC in a long‐term field study in Ontario, Canada. The cropping system is based on rotations including corn, alfalfa, cereals, soybeans and a red clover cover crop. Tillage practices of conventional (moldboard plow, CT) and conservation (no‐till, NT) were applied to each cropping system. A 130‐day laboratory incubation was conducted to measure the potentially mineralizable SOC. The thermal stability and molecular structure of SOC were investigated using thermal analysis‐programmed pyrolysis (PP) and solid‐state 13C cross polarization/total sideband suppression magic angle spinning nuclear magnetic resonance (CP/TOSS MAS NMR) spectroscopy, respectively. The SOC stocks were larger under NT practices and the crop rotations incorporating alfalfa and cover crops. Under NT practices, an abundance of aromatic‐C components was observed, however, soil under CT showed an abundance of aliphatic‐C compounds (p < 0.001), with a higher alkyl/O‐alkyl‐C ratio, indicating a higher degree of SOC decomposition. Soil under rotations that included soybeans demonstrated a significant increase in aliphatic‐C components, whereas those with cover cropping exhibited an enrichment in O‐alkyl‐C groups (p < 0.05), representing the presence of more resistant and easily decomposable SOC constituents, respectively. The results demonstrated that the thermal stability of SOC in CT systems was higher than that of NT practices (p < 0.05), while NT practices and crop rotations including cover crops are better capable of conserving the labile pool of SOC. Our findings confirmed the correlations among the parameters that characterize both the labile and stable pools of SOC as determined by the methods employed in this study. These results demonstrated that agricultural management practices significantly influence the chemical composition and thermal stability of soil organic matter (SOM), which can have significant impacts on soil health and C sequestration potential. [ABSTRACT FROM AUTHOR]

The TiMnSi2-type (space group Pbam) germanides ScTGe2 (T = Fe, Co, Ru, Rh) were synthesized from the elements by arc-melting. Single crystals were grown by annealing sequences of the arc-melted buttons in an induction furnace. The structures of ScFeGe2, ScRuGe2 and ScRhGe2 were refined from single-crystal X-ray diffraction data. In ScRuGe2, the ruthenium atoms have distorted octahedral germanium coordination (242–268 pm Ru–Ge). Three trans-face-sharing octahedra form a sub-unit which is condensed via common edges in c direction and connected via common corners with four adjacent blocks, forming a three-dimensional [RuGe2 type] substructure. The two crystallographically independent scandium sites have coordination numbers 15 (Sc1@Ge8Ru4Sc3) and 17 (Sc2@Ge7Ru6Sc4). Electronic band structure calculations for ScCoGe2 and ScRuGe2 show a net charge transfer from the scandium to the transition metal and germanium atoms, leading to a description with polyanionic networks Scδ+[TGe2]δ−. The two crystallographically independent Sc sites are easily distinguishable by 45Sc magic-angle spinning (MAS)-NMR spectroscopy. Isotropic chemical shift values and nuclear electric quadrupolar interaction parameters were deduced from an analysis of the triple-quantum (TQ)-MAS NMR spectra. The electric field gradient parameters deduced from these experiments are in good agreement with quantum-chemical calculations using the Wien2k code. Likewise, the two crystallographically independent iron sites in ScFeGe2 could be discriminated in the 57Fe Mößbauer spectra through their isomer shifts and quadrupole splitting parameters: δ = 0.369(1) mm s−1 and ∆EQ = 0.232(2) mm s−1 for Fe1 and δ = 0.375(2) mm s−1 and ∆EQ = 0.435(4) mm s−1 for Fe2 (data at T = 78 K). [ABSTRACT FROM AUTHOR]

Green tomato (Physalis ixocarpa) is a specie native to Mexico, and it is known as "tomatillo" or "husk tomato". The fruit contains vitamins, minerals, phenolic compounds, and steroidal lactones, presenting antimicrobial activity and antinarcotic effects. Therefore, it is not only used in traditional Mexican cuisine, but also in traditional medicine to relieve some discomforts such as fever, cough, and amygdalitis. However, it is a perishable fruit whose shelf life is very short. As a part of the peel, cuticle, and epicuticular waxes represent the most important part in plant protection, and the specific composition and structural characterization are significant to know how this protective biopolymer keeps quality characteristics in fresh fruits. P. ixocarpa cutin was obtained by enzymatic treatments (cellulase, hemicellulose, and pectinase) and different concentrations of TFA, and studied through Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CPMAS 13C NMR), Ultra-High Performance Liquid Chromatography coupled to Mass Spectrometry (UHPLC-MS), and was morphologically characterized by Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy (SEM). The main constituents identified under the basis of UHPLC-MS analysis were 9,10,18-trihydroxy-octadecanoic acid and 9,10-epoxy-18-hydroxy-octadecanoic acid with 44.7 and 37.5%, respectively. The C16 absence and low occurrence of phenolic compounds, besides the presence of glandular trichomes, which do not allow a continuous layer on the surface of the fruit, could be related to a lower shelf life compared with other common fruits such as tomato (Solanum lycopersicum). [ABSTRACT FROM AUTHOR]

Higher rates of peanut allergy have been observed in countries that commonly roast peanuts prior to consumption. Despite the importance of understanding the role of thermal processing in allergy and on peanut composition, studies toward generating signatures that identify molecular contents following processing are scant. Here, we identified spectral signatures to track changes and differences in the molecular composition of peanuts under raw, roasted, and high-pressure and high-temperature autoclaved conditions. We analyzed both the solid flesh of the seed and solutions derived from soaking peanuts using High-Resolution Magic Angle Spinning (HR-MAS) and solution 1H Nuclear Magnetic Resonance (NMR) spectroscopy, respectively. The NMR spectra of intact peanuts revealed triglycerides as the dominant species, assigned on the basis of multiplets at 4.1 and 4.3 ppm, and corresponding defatted flours revealed the presence of sugars. Sucrose assigned based on a doublet at 5.4 ppm (anomeric proton), and triglycerides were the most abundant small molecules observed, with little variation between conditions. Soaked peanut solutions were devoid of lipids, and their resulting spectra matched the profiles of defatted peanuts. Spectral signatures resulting from autoclaving differed strikingly between those from raw and roasted peanuts, with considerable line-broadening in regions corresponding to proteins and amino-acid side chains, from 0.5 to 2.0 ppm and 6.5 to 8.5 ppm. Taken together, by using complementary NMR methods to obtain a fingerprint of the molecular components in peanuts, we demonstrated that autoclaving led to a distinct composition, likely resulting from the hydrolytic cleavage of proteins, the most important molecule of the allergic reaction. [ABSTRACT FROM AUTHOR]

The influence of Al2O3 addition on the precipitation of NaYF4 crystals in oxyfluoride glasses has been investigated through the thermal, structural, and optical characterization of the parent glasses and corresponding glass–ceramics (GCs). The high‐resolution transmission electron microscopy analysis of the GC with 5 mol% of Al2O3 shows the presence of phase‐separated droplets about 69 nm in size containing several NaYF4 nanocrystals with the diameter of about 10–15 nm. Raman and magic angle spinning nuclear magnetic resonance (MAS‐NMR) spectroscopy were used to examine the structural changes attributed to the addition of Al2O3. The 19F MAS‐NMR analysis indicated that fluorine atoms are present in different chemical environments (Na–F, Na–Si–F, Na–Al–F, and NaYF4). The increasing amount of Al2O3 reduces the crystallization of NaYF4 phase due to the increased fraction of fluorine bound in Na–Al–F environments. The visible luminescence investigation of the glasses and GCs demonstrated that the intensity of Er3+ ions emission transitions in the GCs was higher than that of the parent glass. This difference was attributed to the presence of Er3+ ions bound in NaYF4 crystalline phase. Further evidence that the Er3+ ions were present in NaYF4 phase was provided by the fact that the excited level Er3+:4S3/2 lifetime was increased in GCs as compared to parent glass. [ABSTRACT FROM AUTHOR]

The initial changes in the microstructure of alkali‐activated slag cement (AAS) characterize the rheological behavior, initial structuration, and setting times of the mixture. In this study, the relationships among the rheological behavior, solidification process, and nanostructure changes of sodium hydroxide‐activated slag (NH–AAS) and sodium silicate‐activated slag (SS–AAS) pastes over time are investigated by small amplitude oscillation shear test, isothermal calorimetry, scanning electron microscopy analyses, and 1H–29Si cross‐polarization magic‐angle spinning nuclear magnetic resonance spectroscopy (CP MAS NMR) and 29Si MAS NMR spectroscopy. Test results showed that the NH–AAS reaches its initial setting time following a continuously proceeding structuration process, whereas the SS–AAS reaches its initial setting with an abrupt increase in the structuration process. At their initial setting times, the NH–AAS and SS–AAS mixtures release similar heat and reach a similar reaction degree. The SS–AAS mixture had more N–A–S–H formation than C–A–S–H at the initial setting time. On the other hand, the amount of C–A–S–H was similar to N–A–S–H in the NH–AAS mixture. The gradual N–A–S–H gel degradation to form C–A–S–H was observed during the acceleration period for the SS–AAS mixture. [ABSTRACT FROM AUTHOR]

Mg2+ and silicate ions are important ionic species in bone formation. Previously, the authors' group reported a 15MgO–15CaO–8P2O5–4SiO2 glass (silicophosphate invert glass [spIG]) containing orthophosphate and orthosilicate structures. Mg2+ and Ca2+ ions in the glass preferentially formed Si–O–Mg and P–O–Ca bonds, respectively, suppressing the release amount of silicate ions in a tris–HCl buffer solution (TBS). In this study, a new 15MgO–15CaO–5P2O5–10SiO2 invert glass without a silicate 3D‐network structure was prepared via a melt‐quenching method. The new glass exhibits an improved silicate‐ion release ability that promotes bone formation. The dissolution amounts of Ca2+ and phosphate ions from the glass into a TBS were similar to those of spIG, but the amounts of Mg2+ and silicate ions increased by ∼2 and ∼5 times, respectively. 31P and 29Si magic‐angle spinning nuclear magnetic resonance spectroscopic analyses showed that the glass was composed of orthophosphate and chain silicate structures. Even when the silica content exceeded that of spIG, the formation of a silicate 3D‐network was suppressed. The O1s X‐ray photoelectron spectra indicated that (Si, P)–O–Mg bonds contribute to the glass formation. In a glass model based on classical molecular dynamics, the oxygen coordination numbers of Mg and Ca were determined as 4–7 and 5–8, respectively. Mg2+ ions are predominantly responsible for bridging the silicate/phosphate structures in this glass and play an important role in tuning the glass formation and the release amount of silicate ions. [ABSTRACT FROM AUTHOR]

Single metal atoms supported on silica are attractive catalysts, and precise control of the local environment around the metal species is essential. Crystalline silica is useful as an efficient support for the incorporation of well-defined metal sites. Dimethyltin species were regularly grafted onto the layer surfaces of layered octosilicate, a type of two-dimensional (2D) crystalline silica. Dimethyltin dichlorides react with the surface silanol (SiOH) groups of the silicate layers. The formation of Si–O–Sn bonds was confirmed by 29Si magic-angle spinning (MAS) NMR. X-ray absorption fine structure (XAFS) analysis showed the four-coordinated Sn species. These results suggested the presence of well-defined dipodal dimethyltin species on the layer surfaces. The degree of modification of the silanol groups with the dimethyltin groups increased with increasing amounts of dimethyltin dichloride; however, the maximum degree of modification was approximately 50%. This value was interpreted as an alternate modification of the octosilicate reaction sites with dimethyltin groups. These results demonstrate the potential for developing highly active single metal catalysts with a high density of regularly arranged active sites on high surface area supports. [ABSTRACT FROM AUTHOR]

Superionic solid electrolytes (SEs) are essential for bulk‐type solid‐state battery (SSB) applications. Multicomponent SEs are recently attracting attention for their favorable charge‐transport properties, however a thorough understanding of how configurational entropy (ΔSconf) affects ionic conductivity is lacking. Here, we successfully synthesized a series of halogen‐rich lithium argyrodites with the general formula Li5.5PS4.5ClxBr1.5‐x (0≤x≤1.5). Using neutron powder diffraction and 31P magic‐angle spinning nuclear magnetic resonance spectroscopy, the S2−/Cl−/Br− occupancy on the anion sublattice was quantitatively analyzed. We show that disorder positively affects Li‐ion dynamics, leading to a room‐temperature ionic conductivity of 22.7 mS cm−1 (9.6 mS cm−1 in cold‐pressed state) for Li5.5PS4.5Cl0.8Br0.7 (ΔSconf=1.98R). To the best of our knowledge, this is the first experimental evidence that configurational entropy of the anion sublattice correlates with ion mobility. Our results indicate the possibility of improving ionic conductivity in ceramic ion conductors by tailoring the degree of compositional complexity. Moreover, the Li5.5PS4.5Cl0.8Br0.7 SE allowed for stable cycling of single‐crystal LiNi0.9Co0.06Mn0.04O2 (s‐NCM90) composite cathodes in SSB cells, emphasizing that dual‐substituted lithium argyrodites hold great promise in enabling high‐performance electrochemical energy storage. [ABSTRACT FROM AUTHOR]

Multianionic metal hydrides, which exhibit a wide variety of physical properties and complex structures, have recently attracted growing interest. Here we present Sr6N[BN2]2H3, prepared in a solid‐state ampoule reaction at 800 °C, as the first combination of nitridoborate, nitride and hydride anions within a single compound. The crystal structure was solved from single‐crystal X‐ray and neutron powder diffraction data in space group P21/c (no. 14), revealing a three‐dimensional network of undulated layers of nitridoborate units, strontium atoms and hydride together with nitride anions. Magic angle spinning (MAS) NMR and vibrational spectroscopy in combination with quantum chemical calculations further confirm the structure model. Electrochemical measurements suggest the existence of hydride ion conductivity, allowing the hydrides to migrate along the layers. [ABSTRACT FROM AUTHOR]

Multianionic metal hydrides, which exhibit a wide variety of physical properties and complex structures, have recently attracted growing interest. Here we present Sr6N[BN2]2H3, prepared in a solid‐state ampoule reaction at 800 °C, as the first combination of nitridoborate, nitride and hydride anions within a single compound. The crystal structure was solved from single‐crystal X‐ray and neutron powder diffraction data in space group P21/c (no. 14), revealing a three‐dimensional network of undulated layers of nitridoborate units, strontium atoms and hydride together with nitride anions. Magic angle spinning (MAS) NMR and vibrational spectroscopy in combination with quantum chemical calculations further confirm the structure model. Electrochemical measurements suggest the existence of hydride ion conductivity, allowing the hydrides to migrate along the layers. [ABSTRACT FROM AUTHOR]

Introduction: Plastics used in everyday materials accumulate as waste in the environment and degrade over time. The impacts of the resulting particulate micro- and nanoplastics on human health remain largely unknown. In pregnant mice, we recently demonstrated that exposure to nanoplastics throughout gestation and during lactation resulted in changes in brain structure detected on MRI. One possible explanation for this abnormal postnatal brain development is altered fetal brain metabolism. Objectives: To determine the effect of maternal exposure to nanoplastics on fetal brain metabolism. Methods: Healthy pregnant CD-1 mice were exposed to 50 nm polystyrene nanoplastics at a concentration of 106 ng/L through drinking water during gestation. Fetal brain samples were collected at embryonic day 17.5 (n = 18–21 per group per sex) and snap-frozen in liquid nitrogen. Magic angle spinning nuclear magnetic resonance was used to determine metabolite profiles and their relative concentrations in the fetal brain. Results: The relative concentrations of gamma-aminobutyric acid (GABA), creatine and glucose were found to decrease by 40%, 21% and 30% respectively following maternal nanoplastic exposure when compared to the controls (p < 0.05). The change in relative concentration of asparagine with nanoplastic exposure was dependent on fetal sex (p < 0.005). Conclusion: Maternal exposure to polystyrene nanoplastics caused abnormal fetal brain metabolism in mice. The present study demonstrates the potential impacts of nanoplastic exposure during fetal development and motivates further studies to evaluate the risk to human pregnancies. [ABSTRACT FROM AUTHOR]

Composites made from carbon and nanominerals show great potential for thermal phase change materials, environmental water treatment, and biomass conversion. In 2019, a micro and nano-quartz-carbon ore was discovered in Feng-cheng City, Jiangxi Province. The study of the structural and physicochemical changes of quartz-carbon ore (QZC) during calcination is essential for the preparation of QZC-based composites and to broaden their application areas. Firstly, the SiO2 crystal structure evolution of QZC during calcination was investigated using in-situ X-ray diffraction (XRD), 29Si magic-angle sample spinning nuclear magnetic resonance (MAS NMR), and Fourier transform infrared FTIR spectroscopy. Then, the changes in carbon during calcination were investigated using Raman spectroscopy, 13C MAS NMR, and X-ray photoelectron spectroscopy (XPS). In addition, changes in the QZC morphology were observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Finally, the evolution of the physicochemical properties of QZC during calcination was revealed using thermogravimetric (TG), Brunauer–Emmet–Teller (BET), resistivity, thermal conductivity, and zeta potential techniques. [ABSTRACT FROM AUTHOR]

CuZn-based catalysts are widely used in CO2 hydrogenation, which may effectively convert CO2 to methanol and alleviate CO2 emission issues. The precise design of a model catalyst with a clear atomic structure is crucial in studying the relationship between structure and catalytic activity. In this work, a one-pot strategy was used to synthesize CuZn@ZSM-5 catalysts with approximately two Cu atoms and one Zn atom per unit cell. Atomic Cu and Zn species are confirmed to be located in the [54.6.102] and [62.104] tilings, respectively, by using magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), synchrotron X-ray powder diffraction (SXRD) and high-signal-to-noise-ratio annular dark field scanning transmission electron microscopy (High SNR ADF-STEM). Catalytic hydrogenation of CO2 to methanol was used as a model reaction to investigate the activity of the catalyst with confined active species. Compared to the Cu@ZSM-5, Zn@ZSM-5 and their mixture, the CuZn@ZSM-5 catalyst with a close Cu–Zn distance of 4.5 Å achieves a comparable methanol space–time yield (STY) of 92.0 mgmethanol·gcatal−1·h−1 at 533 K and 4 MPa with high stability. This method is able to confine one to three metal atoms in the zeolite channel and avoid migration and agglomeration of the atoms during the reaction, which maintains the stability of the catalyst and provides an efficient way for adjustment of the type and number of metal atoms along with the distances between them in zeolites. [ABSTRACT FROM AUTHOR]

In this paper, the influence of diamines on the intrinsic structure and molecular mobility of cellulosic complexes is discussed. Cellulose was pre-swollen by ethylenediamine then put in contact with a series of aliphatic diamines at a stoechiometric ratio. These materials were then characterized by Wide Angle X-Ray diffraction (WAXS) and solid-state 13 C NMR spectroscopy. It was observed by WAXS that diamines are able to swell cellulose along the (010) crystallographic plane and are able to modify unit cell angle γ of cellulose monoclinic structure. Moreover according to their periodicity, ordered- or disordered-phases structures were identified in such cellulosic complexes by Cross Polarization - Magic Angle Spinning (CP-MAS) 13 C NMR spectroscpy. Two-dimensional Wide-line Separation (2D WISE) and T 1 relaxation time 13 C NMR spectroscopy experiments showed that complexes do exhibit molecular motions between 23 and 90 ∘ C. Modulated Differential Scanning Calorymetry (MDSC) further showed the presence of two glass transition temperatures T g , which were attributed, in combination with the 13 C NMR spectroscopy observations through a multiscale approach, to relaxation motions internal to the diamines chemical structure and to the motion of cellulose–diamine planes respectively. [ABSTRACT FROM AUTHOR]

Photosynthetic light-harvesting complexes have a remarkable capacity to perform robust photo-physics at ambient temperatures and in fluctuating environments. Protein conformational dynamics and membrane mobility are processes that contribute to the light-harvesting efficiencies and control photoprotective responses. This short review describes the application of magic angle spinning nuclear magnetic resonance (NMR) spectroscopy for characterizing the structural dynamics of pigment, protein, and thylakoid membrane components related to light harvesting and photoprotection. I will discuss the use of dynamics-based spectral editing solid-state NMR for distinguishing rigid and mobile components and assessing protein, pigment, and lipid dynamics on sub-nanosecond to millisecond timescales. Dynamic spectral editing NMR has been applied to investigate light-harvesting complex II protein conformational dynamics inside lipid bilayers and in native membranes. Furthermore, we used the NMR approach to assess thylakoid membrane dynamics. Finally, it is shown that dynamics-based spectral editing NMR for reducing spectral complexity by filtering motion-dependent signals enabled us to follow processes in live photosynthetic cells. [ABSTRACT FROM AUTHOR]

A new heteronuclear decoupling pulse sequence is introduced, dubbed ROtor-Synchronized Phase-Alternated Cycles (ROSPAC). It is based on a partial refocusing of the coherences (spin operator products or cross-terms) [Filip et al., J. Mag. Reson. 176, 2 (2005)] responsible for transverse spin-polarization dephasing, on the irradiation of a large pattern of radio-frequencies, and on a significant minimization of the cross-effects implying 1H chemical-shift anisotropy. Decoupling efficiency is analyzed by numerical simulations and experiments and compared to that of established decoupling sequences [swept-frequency two-pulse phase-modulated (TPPM), TPPM, small phase incremental alternation (SPINAL), refocused Continuous-wave (CWApa), and Rotor-Synchronized Hahn-Echo pulse train (RS-HEPT)]. It was found that ROSPAC offers good 1H offset robustness for a large range of chemical shifts and low radio-frequency (RF) powers, and performs very well in the ultra-fast magic-angle spinning (MAS) regime, where it is almost independent from RF power and permits it to avoid rotary-resonance recoupling conditions (v1 = nvr, n = 1, 2). It has the advantage that only the pulse lengths require optimization and has a low duty cycle in the pulsed decoupling regime. The efficiency of the decoupling sequence is demonstrated on a model microcrystalline sample of the model protein domain GB1 at 100 kHz MAS at 18.8 T. [ABSTRACT FROM AUTHOR]

Dynamic Nuclear Polarization (DNP) is transforming the landscape of solid-state characterization for both biological solids and functional materials. By transferring electron spin polarization to coupled nuclear spins under microwave irradiation, DNP increases NMR sensitivity by several orders of magnitude. However, the mechanism of DNP transfer and its efficiency under magic-angle spinning (MAS) significantly differs from that under static conditions. This primer article provides a comprehensive and pedagogical explanation of the theoretical aspects of MAS-DNP, with a specific focus on the cross-effect mechanism. A clear understanding of the nuances of MAS-DNP is crucial for improving its efficiency and extending its application to high magnetic fields and fast MAS conditions. To this end, the article proposes a guideline for synthetic chemists to develop DNP polarizing agents under these experimental conditions.

Solid-state nuclear magnetic resonance can be enhanced using unpaired electron spins with a method known as dynamic nuclear polarization (DNP). Fundamentally, DNP involves ensembles of thousands of spins, a scale that is difficult to match computationally. This scale prevents us from gaining a complete understanding of the spin dynamics and applying simulations to design sample formulations. We recently developed an ab initio model capable of calculating DNP enhancements in systems of up to ∼1000 nuclei; however, this scale is insufficient to accurately simulate the dependence of DNP enhancements on radical concentration or magic angle spinning (MAS) frequency. We build on this work by using ab initio simulations to train a hybrid model that makes use of a rate matrix to treat nuclear spin diffusion. We show that this model can reproduce the MAS rate and concentration dependence of DNP enhancements and build-up time constants. We then apply it to predict the DNP enhancements in core–shell metal-organic-framework nanoparticles and reveal new insights into the composition of the particles' shells. [ABSTRACT FROM AUTHOR]

Background: Prostate cancer (PC) is a heterogenous multifocal disease ranging from indolent to lethal states. For improved treatment-stratification, reliable approaches are needed to faithfully differentiate between high- and low-risk tumors and to predict therapy response at diagnosis. Methods: A metabolomic approach based on high resolution magic angle spinning nuclear magnetic resonance (HR MAS NMR) analysis was applied on intact biopsies samples (n = 111) obtained from patients (n = 31) treated by prostatectomy, and combined with advanced multi- and univariate statistical analysis methods to identify metabolomic profiles reflecting tumor differentiation (Gleason scores and the International Society of Urological Pathology (ISUP) grade) and subtypes based on tumor immunoreactivity for Ki67 (cell proliferation) and prostate specific antigen (PSA, marker for androgen receptor activity). Results: Validated metabolic profiles were obtained that clearly distinguished cancer tissues from benign prostate tissues. Subsequently, metabolic signatures were identified that further divided cancer tissues into two clinically relevant groups, namely ISUP Grade 2 (n = 29) and ISUP Grade 3 (n = 17) tumors. Furthermore, metabolic profiles associated with different tumor subtypes were identified. Tumors with low Ki67 and high PSA (subtype A, n = 21) displayed metabolite patterns significantly different from tumors with high Ki67 and low PSA (subtype B, n = 28). In total, seven metabolites; choline, peak for combined phosphocholine/glycerophosphocholine metabolites (PC + GPC), glycine, creatine, combined signal of glutamate/glutamine (Glx), taurine and lactate, showed significant alterations between PC subtypes A and B. Conclusions: The metabolic profiles of intact biopsies obtained by our non-invasive HR MAS NMR approach together with advanced chemometric tools reliably identified PC and specifically differentiated highly aggressive tumors from less aggressive ones. Thus, this approach has proven the potential of exploiting cancer-specific metabolites in clinical settings for obtaining personalized treatment strategies in PC. [ABSTRACT FROM AUTHOR]

Two families of phosphorhydrazone dendrons having either an azide or an alkyne linked to the core and diverse types of pyridine derivatives as terminal functions have been synthesized and characterized. These dendrons were grafted via click reaction to graphene oxide (GO) functionalized with either alkyne or azide functions, respectively. The resulting modified‐GO and GO‐dendrons materials have been characterized by Fourier Transform Infrared (FTIR), Raman spectroscopy (RS), and Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) analyses. In addition, the free dendrons and the dendrons grafted to GO were tested toward cancerous (HCT116) and non‐cancerous (RPE1) cell lines. [ABSTRACT FROM AUTHOR]

The synthesis of biocompatible and bioresorbable composite materials, such as a "polymer matrix-mineral constituent," stimulating the natural growth of living tissues and the restoration of damaged parts of the body, is one of the challenging problems in regenerative medicine and materials science. Composite films of bioresorbable polymer of polyvinylpyrrolidone (PVP) and hydroxyapatite (HA) were obtained. HA was synthesized in situ in the polymer solution. We applied electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) approaches to study the composite films' properties. The application of EPR in two frequency ranges allowed us to derive spectroscopic parameters of the nitrogen-based light and radiation-induced paramagnetic centers in HA, PVP and PVP-HA with high accuracy. It was shown that PVP did not significantly affect the EPR spectral and relaxation parameters of the radiation-induced paramagnetic centers in HA, while light-induced centers were detected only in PVP. Magic angle spinning (MAS) 1H NMR showed the presence of two signals at 4.7 ppm and −2.15 ppm, attributed to "free" water and hydroxyl groups, while the single line was attributed to 31P. NMR relaxation measurements for 1H and 31P showed that the relaxation decays were multicomponent processes that can be described by three components of the transverse relaxation times. The obtained results demonstrated that the applied magnetic resonance methods can be used for the quality control of PVP-HA composites and, potentially, for the development of analytical tools to follow the processes of sample treatment, resorption, and degradation. [ABSTRACT FROM AUTHOR]

Tetrafluoromethane (CF4), the simplest perfluorocarbon (PFC), has the potential to exacerbate global warming. Catalytic hydrolysis is a viable method to degrade CF4, but fluorine poisoning severely restricts both the catalytic performance and catalyst lifetime. In this study, Ga is introduced to effectively assists the defluorination of poisoned Al active sites, leading to highly efficient CF4 decomposition at 600 °C with a catalytic lifetime exceeding 1,000 hours. 27Al and 71Ga magic‐angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that the introduced Ga exists as tetracoordinated Ga sites (GaIV), which readily dissociate water to form Ga−OH. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density function theory (DFT) calculations confirmed that Ga−OH assists the defluorination of poisoned Al active sites via a dehydration‐like process. As a result, the Ga/Al2O3 catalyst achieved 100 % CF4 decomposition keeping an ultra‐long catalytic lifetime and outperforming reported results. This work proposes a new approach for efficient and long‐term CF4 decomposition by promoting the regeneration of active sites. [ABSTRACT FROM AUTHOR]