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We investigated the stable isotope hydrology of Sable Island, Nova Scotia, Canada over a five year period from September, 2017 to August, 2022. The δ2H and δ18O values of integrated monthly precipitation were weakly seasonal and ranged from –66 to –15 ‰ and from –9.7 to –1.9 ‰, respectively. Fitting these monthly precipitation data resulted in a local meteoric water line (LMWL) defined by: δ2H = 7.22 ± 0.21 · δ18O + 7.50 ± 1.22 ‰. Amount-weighted annual precipitation had δ2H and δ18O values of –36 ± 11 ‰ and –6.1 ± 1.4 ‰, respectively. Deep groundwater had more negative δ2H and δ18O values than mean annual precipitation, suggesting recharge occurs mainly in the winter, while shallow groundwater had δ2H and δ18O values more consistent with mean annual precipitation or mixing of freshwater with local seawater. Surface waters had more positive values and showed evidence of isolation from the groundwater system. The stable isotopic compositions of plant (leaf) water, on the other hand, indicate plants use groundwater as their source. Fog had δ2H and δ18O values that were significantly more positive than those of local precipitation, yet had similar 17O-excess values. δ2H values of horsehair from 4 individuals lacked seasonality, but had variations typical to those of precipitation on the island. Differences in mean δ2H values of horsehair were statistically significant and suggest variations in water use may exist between spatially disparate horse communities. Our results establish an important initial framework for ongoing isotope studies of feral horses and other wildlife on Sable Island. [ABSTRACT FROM AUTHOR]

In this study, we have investigated the oxygen isotope compositions (δ17O and δ18O) of modern rain and ice cores using published isotopic data. We find that, contrary to existing interpretations, precipitation δ17O is influenced by two factors: mass-dependent fractionation (MDF), which occurs during ocean evaporation, and mass-independent fractionation (MIF), which happens in the stratosphere. The MDF contribution remains constant and can be understood by studying tropical rain, as the overall movement of mass in the tropics is upward toward the stratosphere. On the other hand, the MIF effect comes from the mixing of stratospheric air in the troposphere, which is a result of the Brewer–Dobson circulation. This MIF effect on precipitation 17O increases from the tropics toward the poles and is observed consistently in modern precipitation and ice cores. The relative δ17O and δ18O composition, denoted as ∆'17O, in modern precipitation can be calibrated with surface air temperature, creating a new and independent tool for estimating past temperatures. We used this calibration along with the ∆'17O of Antarctic and Greenland ice cores, and our reconstructed past temperatures are in excellent agreement with those derived from borehole thermometry or gas phase analysis of air trapped in the ice. The ∆'17O method overcomes the problems associated with using δ18O alone for paleothermometry. Our findings align with climate models that suggest a weakening of the Brewer–Dobson circulation during the Last Glacial Maximum. Furthermore, our approach could be used to monitor future changes in stratosphere–troposphere mass exchange in response to a warming climate caused by increasing greenhouse gases. [ABSTRACT FROM AUTHOR]

The nitrogen and oxygen (δ15N, δ18O, δ17O) stable isotopic compositions of nitrate ( N O 3 – ) are crucial tracers of nutrient N sources and dynamics in aquatic and atmospheric systems. Methods to reduce aqueous N O 3 – to N2O gas (microbial or Cd method) before 15N and 18O isotope analyses require multi-step conversion or toxic chemicals, and 17O in N2O cannot be disentangled by IRMS due to isobaric interferences. This technical note describes the automation of the stable-isotope analyses of nitrate by coupling the new Ti method with a headspace autosampler and an N2O triple-isotope laser analyzer based on off-axis integrated cavity output spectroscopy. The automation yielded accurate and precise results for routine determinations of δ15N, δ18O, and δ17O values for aqueous nitrate in environmental waters. Systematic corrections were required for cavity pressure, N2O concentration and water vapour content to obtain the highest precision for all three isotopic ratios. For the first time, an automated laser-based system facilitates routine low-cost triple isotope analyses in studies where high-temporal resolution isotope analyses of NO3− are required but have been, until now, cost-prohibitive and time-consuming (e.g. atmospheric N pollution). [ABSTRACT FROM AUTHOR]

Abstract Background Indirect 1H-magnetic resonance (MR) imaging of 17O-labelled water allows imaging in vivo dynamic changes in water compartmentalisation. Our aim was to describe the feasibility of indirect 1H-MR methods to evaluate the effect of H2 17O on the MR relaxation rates by using conventional a 3-T equipment and voxel-wise relaxation rates. Methods MR images were used to calculate the R1, R2, and R2* relaxation rates in phantoms (19 vials with different H2 17O concentrations, ranging from 0.039 to 5.5%). Afterwards, an experimental animal pilot study (8 rats) was designed to evaluate the in vivo relative R2 brain dynamic changes related to the intravenous administration of 17O-labelled water in rats. Results There were no significant changes on the R1 and R2* values from phantoms. The R2 obtained with the turbo spin-echo T2-weighted sequence with 20-ms echo time interval had the higher statistical difference (0.67 s−1, interquartile range 0.34, p < 0.001) and Spearman correlation (rho 0.79). The R2 increase was adjusted to a linear fit between 0.25 and 5.5%, represented with equation R2 = 0.405 concentration + 0.3215. The highest significant differences were obtained for the higher concentrations (3.1–5.5%). The rat brain MR experiment showed a mean 10% change in the R2 value after the H2 17O injection with progressive normalisation. Conclusions Indirect 1H-MR imaging method is able to measure H2 17O concentration by using R2 values and conventional 3-T MR equipment. Normalised R2 relative dynamic changes after the intravenous injection of a H2 17O saline solution provide a unique opportunity to map water pathophysiology in vivo, opening the analysis of aquaporins status and modifications by disease at clinically available 3-T proton MR scanners.

Background: Indirect 1H-magnetic resonance (MR) imaging of 17O-labelled water allows imaging in vivo dynamic changes in water compartmentalisation. Our aim was to describe the feasibility of indirect 1H-MR methods to evaluate the effect of H217O on the MR relaxation rates by using conventional a 3-T equipment and voxel-wise relaxation rates. Methods: MR images were used to calculate the R1, R2, and R2* relaxation rates in phantoms (19 vials with different H217O concentrations, ranging from 0.039 to 5.5%). Afterwards, an experimental animal pilot study (8 rats) was designed to evaluate the in vivo relative R2 brain dynamic changes related to the intravenous administration of 17O-labelled water in rats. Results: There were no significant changes on the R1 and R2* values from phantoms. The R2 obtained with the turbo spin-echo T2-weighted sequence with 20-ms echo time interval had the higher statistical difference (0.67 s−1, interquartile range 0.34, p < 0.001) and Spearman correlation (rho 0.79). The R2 increase was adjusted to a linear fit between 0.25 and 5.5%, represented with equation R2 = 0.405 concentration + 0.3215. The highest significant differences were obtained for the higher concentrations (3.1–5.5%). The rat brain MR experiment showed a mean 10% change in the R2 value after the H217O injection with progressive normalisation. Conclusions: Indirect 1H-MR imaging method is able to measure H217O concentration by using R2 values and conventional 3-T MR equipment. Normalised R2 relative dynamic changes after the intravenous injection of a H217O saline solution provide a unique opportunity to map water pathophysiology in vivo, opening the analysis of aquaporins status and modifications by disease at clinically available 3-T proton MR scanners. [ABSTRACT FROM AUTHOR]

Seven magnesium‐containing aluminoborosilicate glasses, with three to five oxides, have been studied through comprehensive multinuclear solid‐state NMR (11B, 27Al, 29Si, 23Na, 17O, and 25Mg) and Raman spectroscopy. The progressive addition of cations and the substitution of sodium and calcium by magnesium illuminate the impact of magnesium on the glass structure. The proportion of tri‐coordinated boron drastically increased with magnesium addition, demonstrating the poor charge‐compensating capabilities of magnesium in tetrahedral boron units. Oxygen‐17 NMR showed the formation of mixing sites containing both Na and Mg near nonbridging oxygen sites. Furthermore, a high magnesium content appears to result in the formation of two subnetworks (boron and silicon rich) with different polymerization degrees as well as to promote the formation of high‐coordination aluminum sites (Al[V] and Al[VI]). Finally, magnesium coordination ranging from 4 to 6, with a mean value shifting from 5 to 6 along the series, suggests that magnesium might endorse an intermediate role in these glasses. [ABSTRACT FROM AUTHOR]

Oxygen‐17 and deuterium are two quadrupolar nuclei that are of interest for studying the structure and dynamics of materials by solid‐state nuclear magnetic resonance (NMR). Here, 17O and 2H NMR analyses of crystalline ibuprofen and terephthalic acid are reported. First, improved 17O‐labelling protocols of these molecules are described using mechanochemistry. Then, dynamics occurring around the carboxylic groups of ibuprofen are studied considering variable temperature 17O and 2H NMR data, as well as computational modelling (including molecular dynamics simulations). More specifically, motions related to the concerted double proton jump and the 180° flip of the H‐bonded (–COOH)2 unit in the crystal structure were looked into, and it was found that the merging of the C=O and C–OH 17O resonances at high temperatures cannot be explained by the sole presence of one of these motions. Lastly, preliminary experiments were performed with a 2H–17O diplexer connected to the probe. Such configurations can allow, among others, 2H and 17O NMR spectra to be recorded at different temperatures without needing to tune or to change probe configurations. Overall, this work offers a few leads which could be of use in future studies of other materials using 17O and 2H NMR. [ABSTRACT FROM AUTHOR]

Water vapor, the most important greenhouse gas in the atmosphere, has four natural stable isotopologues (H216O, H217O, H218O and HD16O), and their isotopic compositions can be used as hydrological tracers. But the underlying processes and pattern-dynamics of the isotopic compositions of atmospheric water vapor and precipitation in response to various meteorological conditions during monsoon season in a tropical hot and humid region is poorly understood. Here, we present results of H and triple-O-isotopes of water in precipitation and atmospheric water vapor during monsoon season exploiting high-resolution integrated cavity output spectroscopy technique. We observed a distinct temporal variation of the isotopic compositions of water at different phases of the monsoon. The diurnal patterns of the isotopic variations were influenced by the local meteorological factors such as temperature, relative humidity and amount of precipitation. We also investigated the monsoonal dynamics of the second-order isotopic parameters, so-called d-excess and 17O-excess along with the influence of local meteorological factors on isotopic variations to improve our understanding of the underlying isotopic fractionation processes. Consequently, our results provide a unique isotopic-fingerprint dataset of rainwater and atmospheric water vapor for a tropical region and thus shed a new light on hydrological and meteorological processes in the atmosphere. [ABSTRACT FROM AUTHOR]

The procedure of calibrating in-house water standards suitable for routine analyses of triple-isotope composition of water samples using Picarro L2140-i CRDS analyser is presented and discussed. Such standards are indispensable for achieving and maintaining high quality of isotope analyses of water in terms of their precision and accuracy. A set of seven different water standards consisting of three in-house standards and four secondary standards commercially available was calibrated against VSMOW2/SLAP2 primary reference materials. The calibrated standards cover a wide range of isotopic composition, with δ values ranging from close to zero to the values comparable with SLAP2. The apparent consistency of the calibrated values of δ2H, δ18O and d-excess with corresponding certified values for commercially available USGS47-50 standards and the consistency of the calibrated values of δ17O and Δ17O with its literature values for USGS47-48 standards confirm the high quality of the performed calibration. Moreover, the calibration exercise allowed to obtain δ17O and Δ17O values for USGS49 and USGS50 standards, not reported so far. [ABSTRACT FROM AUTHOR]

In the present study we investigated the isotope effects associated with water loss from closed low-density polyethylene (LDPE) bottles via diffusion at temperatures between 4 and 60 °C. While at low temperatures (4 and 10 °C) no substantial diffusional loss of water was observed within storage time, a pronounced loss was found for the experiments at room temperature and 60 °C. The latter was associated with a substantial increase in δ18O, δ17O, and δ2Η values, and a decrease in the deuterium excess. The magnitude of the isotope effects essentially depended on the extent of water evaporation from the closed bottles through the LDPE membrane. [ABSTRACT FROM AUTHOR]

Since 1973, Kunene River water has been carried from the Calueque reservoir in Angola along a 160 km open concrete canal to the town of Oshakati in the central part of the Cuvelai-Etosha Basin and has been supplying drinking water to the most densely populated rural area of Namibia. Despite its importance for the region, intra-seasonal water quality and the technical condition of the canal are not routinely checked. Water samples were collected during four field campaigns right before the onset of the rainy season (November 2013 and 2014), and after the rainy season (June 2014 and May 2015), at 16 sites along the canal for stable water isotopes (deuterium, oxygen-17 and oxygen-18) and hydrochemical analyses. The isotope patterns and chemical composition of the canal water is discussed in comparison to local rain, Kunene source water, surface water and groundwater. Clear isotope enrichment indicates evaporative loss of water. A Craig–Gordon model was used to estimate water loss. The loss increases with distance from the source with a maximum of up to 10 %, depending on the season. The results are discussed in context of water availability, vulnerability and water resources management in this water-scarce area. [ABSTRACT FROM AUTHOR]

Purpose: To design and build a dual‐tuned 17O/1H coil for direct brain oximetry at 3T. Methods: A dual‐tuned 17O/1H coil comprising 2 degenerate mode birdcage coils was constructed to facilitate high‐sensitivity 17O and 1H imaging. In vivo 17O brain images were acquired in a healthy volunteer using a fermat looped orthogonally encoded trajectories sequence, together with high‐resolution structural brain 1H images. Results: Natural abundance 17O images with a nominal resolution of 8 mm3 were acquired in under 20 minutes exhibiting clear delineation of the physiological 17O distribution. One‐millimeter isotropic 1H structural brain images demonstrated excellent quality and anatomical detail using routine clinical imaging sequence parameters and parallel acceleration. Conclusion: A dual‐tuned 17O/1H array was constructed to enable high‐sensitivity 17O and 1H imaging under standard clinical 3 T scanning conditions. [ABSTRACT FROM AUTHOR]

The Rhône River originates in the high Alps and drains an intensely cultivated and industrialised catchment before it discharges to the Gulf of Lion. We investigated the interaction of catchment geomorphology with nitrate sources (atmosphere, agriculture, and nitrification of soil organic matter) and removal processes in large and diverse watersheds on the basis of dual nitrate isotope signatures in river water. In March 2015, we took surface water samples along the Rhône River, including its main tributaries, and measured nutrient concentrations and the stable isotopic composition of nitrate (δ15N, δ18O and Δ17O), and water (δ18O-H2O). Results show that high altitude regions are dominated by nitrate from nitrification in pristine soils and atmospheric deposition, while nitrate in the downstream Rhône River originates mainly from nitrification of agricultural/urban sources. Parallel increases in δ15N and δ18O reflect the influence of primary production. Previous studies suggested robust correlations between land use and δ 15 N - N O 3 – . Based on our observation that nitrate δ15N values at higher altitudes are lower than expected, we assume that lower nitrate δ15N values likely reflect limited nitrate consumption and lower soil nitrogen turnover rates. We propose that correlation between land use and nitrate δ15N is sensitive to slope and geomorphology. [ABSTRACT FROM AUTHOR]

The chance of apparent isotope anomalies either in closed systems at equilibrium or during Rayleigh processes is investigated. The term 'apparent' is chosen to highlight that only mass-dependent fractionation (MDF) processes are considered. A goal is finding analytical expressions that could be used for dealing with the complexity of real systems. For example, the formula for calculating the isotopic fractionation in systems with any desired number of phases involved is identified. Terrestrial samples could exhibit artificially low MIF signatures because Δ is not invariant with the choice of the reference material. An alternative parameter Δ* only depending on β is therefore introduced. The potential transfer of sample points in a three-isotope plot to parallel lines during reversible processes is also investigated. Larger apparent anomalies are expected in systems lacking an infinite reservoir and for large enrichment factors. Pyrite is stable beyond the conditions for a reducing environment and MIF signatures from Archaean sediments could be compatible with reversible processes involving oxidised species. Isotope anomalies in pyrite from the Dresser Formation, Australia, are compatible with post-depositional incorporation of 2–5% sulphur of atmospheric origin. Overall, observed delta values could mainly be related to changes in the local absolute isotope abundances. [ABSTRACT FROM AUTHOR]

The design and implementation of a software package for the analysis of single-crystal NMR data is presented. The SCFit software can treat spectra arising from various interactions: (i) chemical shift tensor only; (ii) chemical shift tensor and quadrupolar coupling tensor; (iii) dipolar and indirect nuclear spin-spin coupling tensors; (iv) all four interactions. The software is demonstrated on recently reported 17O and 31P single-crystal NMR data for triphenylphosphine oxide and for two of its halogen-bonded cocrystals. The 17O single-crystal NMR data represent a case where all four above-mentioned interactions simultaneously affect the spectra. SCFit can fit the chemical shift and quadrupolar coupling in two ways: (i) through an unconstrained fitting process where all tensor parameters are freely optimized or (ii) through a constrained fitting process where the principal components of the tensors may be fixed to values known previously with high precision via the analysis of powder samples. The second strategy is explored in an effort to reduce the number of unknowns in the fitting process; an improvement in the precision of the resulting tensor orientations is noted in some cases. Image 1 • SCFit software for analyzing single-crystal NMR data is described. • Chemical shift, quadrupolar, and spin-spin coupling interactions are treated. • The utility of fixing tensor magnitudes to known values is explored. [ABSTRACT FROM AUTHOR]

18O‐labeled water (Water‐18O) is a widely used starting material of 18F‐labeled diagnostic agents in positron emission tomography (PET). Conventionally, Water‐18O has been separated from other stable oxygen isotope species (16O, 17O) by water distillation or nitric oxide distillation. However, conventional methods are costly and may have safety issues. In 2004, we developed the first unit of our novel oxygen isotope separation process by cryogenic oxygen distillation to overcome these issues. To meet the needs of the market, we built a second unit in 2013 and a third in 2016. We are now operating three commercially viable separation units with a total capacity of 600 kg of Water‐18O per year. [ABSTRACT FROM AUTHOR]

A thorough evaluation of measurement uncertainty together with control of short-term and long-term precision of measurements should be a basis of any successful quality assurance/quality control (QA/QC) strategy aimed at maintaining a high quality of the analytical process. Here we present the results of a comprehensive assessment of the analytical performance of a Picarro L2140-i CRDS laser spectrometer analysing δ2H, δ18O and δ17O in water. The assessment is based on results obtained during 15 months of continuous operation of this instrument (February 2017 to May 2018). The short-term precision of measured and derived quantities was 0.11, 0.036, 0.028, 0.23 ‰ and 11 per meg, for δ2H, δ18O, δ17O, d-excess and Δ17O, respectively, and is comparable to the precision reported by the manufacturer. The long-term precision of the L2140-i, defined as standard uncertainty of the time series of 153 analyses of a laboratory standard conducted throughout 15 months, was roughly two times lower (0.24, 0.053, 0.038, 0.37 ‰ and 21 per meg, for δ2H, δ18O, δ17O, d-excess and Δ17O). In-depth assessment of the measurement uncertainty of a single analysis revealed that assigned uncertainty of the calibration standards is an important component of the uncertainty budget, especially in case of δ2H analysis. [ABSTRACT FROM AUTHOR]

Oxygen is a key atom that maintains biomolecular structures, regulates various physiological processes, and mediates various biomolecular interactions. Oxygen-17 (17O), therefore, has been proposed as a useful probe that can provide detailed information about various physicochemical features of proteins. This is attributed to the facts that (1) 17O is an active isotope for nuclear magnetic resonance (NMR) spectroscopic approaches; (2) NMR spectroscopy is one of the most suitable tools for characterizing the structural and dynamical features of biomolecules under native-like conditions; and (3) oxygen atoms are frequently involved in essential hydrogen bonds for the structural and functional integrity of proteins or related biomolecules. Although 17O NMR spectroscopic investigations of biomolecules have been considerably hampered due to low natural abundance and the quadruple characteristics of the 17O nucleus, recent theoretical and technical developments have revolutionized this methodology to be optimally poised as a unique and widely applicable tool for determining protein structure and dynamics. In this review, we recapitulate recent developments in 17O NMR spectroscopy to characterize protein structure and folding. In addition, we discuss the highly promising advantages of this methodology over other techniques and explain why further technical and experimental advancements are highly desired.

The cerebral metabolic rate of oxygen consumption (CMRO2) is a key metric to investigate the mechanisms involved in neurodegeneration in animal models and evaluate potential new therapies. CMRO2 can be measured by direct 17O magnetic resonance imaging (17O-MRI) of H217O signal changes during inhalation of 17O-labeled oxygen gas. In this study, we built a simple gas distribution system and used 3D zero echo time (ZTE-)MRI at 11.7 T to measure CMRO2 in the APPswe/PS1dE9 mouse model of amyloidosis. We found that CMRO2 was significantly lower in the APPswe/PS1dE9 brain than in wild-type at 12–14 months. We also estimated cerebral blood flow (CBF) from the post-inhalation washout curve and found no difference between groups. These results suggest that the lower CMRO2 observed in APPswe/PS1dE9 is likely due to metabolism impairment rather than to reduced blood flow. Analysis of the 17O-MRI data using different quantification models (linear and 3-phase model) showed that the choice of the model does not affect group comparison results. However, the simplified linear model significantly underestimated the absolute CMRO2 values compared to a 3-phase model. This may become of importance when combining several metabolic fluxes measurements to study neuro-metabolic coupling.

Evaporation of water from the oceans and terrestrial environment governs the global water cycle and climate. Heavy isotope ( 2 H, 18 O, 17 O) enrichment during evaporation led to the development of the well-known Craig-Gordon (C-G) model for quantifying evaporation. Several variables control the H and O isotopic composition of evaporating water including; the isotopic composition of the water, temperature, relative humidity, ambient vapor isotopic composition, diffusion and/or mixing at the water-air interface, and the thermodynamic activity (salinity) of water. Previous C-G modeling efforts considered these controlling variables separately; here we propose a newly unified C-G analytical model that allows for simultaneous quantification of all controlling variables in the evaporation of fresh and saline waters. Our unified model accurately predicted the results of laboratory water evaporation experiments conducted under a variety of molecular diffusion and turbulent diffusion conditions. We demonstrate the general applicability of the model by successfully predicting historical O and H isotope data for fresh and saltwater evaporation obtained from the scientific literature. The unified C-G model allows for improved estimates environmental parameters controlling the H and O isotope fractionation during water evaporation under natural conditions and can be used to better inform modeling efforts in regional and large-scale water balance studies. [ABSTRACT FROM AUTHOR]

Variations in isotopic ratios of water samples collected from three plants functioning on two different desalination processes were evaluated by comparing their measured δ18O, δ17O and the δ2H isotopic ratios before and after desalination using a system based on tunable off-axis integrated-cavity-output diode laser spectroscopy (OA-ICOS). The δ18O, δ17O and the δ2H isotopic ratio measurements for water samples collected before desalination are compared against their peers of desalinated water from two desalination plants on the Arabian Gulf that are operating under the Multistage Flash (MSF) process. Also, variations in the δ18O, δ17O and the δ2H isotopic ratio measurements due to desalination from a Reversal Osmosis (RO) facility in Dhahran, Saudi Arabia were also reported and compared against variations in isotopic composition of water desalinated in two MSF plants. [ABSTRACT FROM AUTHOR]

Abstract: We report a solid‐state 17O (I = 5/2) NMR study of the nitrite ion dynamics in crystalline NaNO2. Variable temperature (VT) 17O NMR spectra were recorded at 3 magnetic fields, 11.7, 14.1, and 21.1 T. The VT 17O NMR data suggest that the NO 2 − ion in the ferroelectric phase of NaNO2 undergoes 2‐fold flip motion about the crystallographic b axis and the corresponding rotational barrier is 68 ± 5 kJ mol−1. We also obtained a 2D 17O EXSY spectrum for a stationary sample of NaNO2 at 250 K, which, in combination with 1D 17O NMR spectral analyses, allowed precise determination of the relative orientation between the 17O quadrupolar coupling and chemical shift tensors in the molecular frame of reference. The experimentally determined 17O NMR tensors for NaNO2 were in agreement with quantum chemical calculations produced by a periodic DFT code BAND. [ABSTRACT FROM AUTHOR]

NMR active nuclei, H, C and N, are usually used for determination of protein structure. However, solution O-NMR application to proteins is extremely limited although oxygen is an essential element in biomolecules. Proteins are oxidized through cysteine residues by two types of oxidation. One is reversible oxidation such as disulphide bonding (Cys-S-S-Cys) and the other is irreversible oxidation to cysteine sulfinic acid (Cys-SO H) and cysteine sulfonic acid (Cys-SO H). Copper,Zinc-superoxide dismutase (SOD1) is a key enzyme in the protection of cells from the superoxide anion radical. The SH group at Cys residue in human SOD1 is selectively oxidized to -SO H and -SO H with atmospheric oxygen, and this oxidized human SOD1 is also suggested to play an important role in the pathophysiology of various neurodegenerative diseases, probably mainly via protein aggregation. Therefore, information on the structural and the dynamics of the oxidized cysteine residue would be crucial for the understanding of protein aggregation mechanism. Although the -SO H group on proteins cannot be directly detected by conventional NMR techniques, we successfully performed the site-specific O-labeling of Cys in SOD1 using $^{17}\textit {O}_{2}$ gas and the O-NMR analysis for the first time. We observed clear O signal derived from a protein molecule and show that O-NMR is a sensitive probe for studying the structure and dynamics of the O-labeled protein molecule. This novel and unique strategy can have great impact on many research fields in biology and chemistry. [ABSTRACT FROM AUTHOR]

This Trends article highlights the recent advances published between 2012 and 2015 in solid-state 17 O NMR for organic and biological molecules. New developments in the following areas are described: (1) new oxygen-containing functional groups, (2) metal organic frameworks, (3) pharmaceuticals, (4) probing molecular motion in organic solids, (5) dynamic nuclear polarization, and (6) paramagnetic coordination compounds. For each of these areas, the author offers his personal views on important problems to be solved and possible future directions. [ABSTRACT FROM AUTHOR]

The element oxygen has three stable isotopes: 16O, 17O, and 18O. For a defined process, a change in 18O/16O scales with the corresponding change in 17O/16O, or the fractionation factors 18α and 17α have a relationship of θ = ln17α/ln18α, in which the triple oxygen isotope exponent θ is relatively fixed but does vary with reaction path, temperature, and species involved. When the small variation is of interest, the distinction of three concepts-θ, S (a slope through data points in δ17O-δ18O space), and C (an arbitrary referencing number for the degree of 17O deviation)-becomes important. Triple oxygen isotope variations can be measured by modern instruments and thus offer an additional line of information on the underlying reaction processes and conditions. Analytical methods and Earth science applications have recently been developed for air oxygen, carbon dioxide, water, silicates, oxides, sulfates, carbonates, and phosphates. [ABSTRACT FROM AUTHOR]

We report synthesis and solid-state NMR characterization of two 17O-labeled platinum anticancer drugs: cis-diammine(1,1-cyclobutane-[17O4]dicarboxylato)platinum(II) (carboplatin) and ([17O4]oxalato)[(1R, 2R)-(-)-1,2-cyclohexanediamine)]platinum(II) (oxaliplatin). Both 17O chemical shift (CS) and quadrupolar coupling (QC) tensors were measured for the carboxylate groups in these two compounds. With the aid of plane wave DFT computations, the 17O CS and QC tensor orientations were determined in the molecular frame of reference. Significant changes in the 17O CS and QC tensors were observed for the carboxylate oxygen atom upon its coordination to Pt(II). In particular, the 17O isotropic chemical shifts for the oxygen atoms directly bonded to Pt(II) are found to be smaller (more shielded) by 200 ppm than those for the non-Pt-coordinated oxygen atoms within the same carboxylate group. Examination of the 17O CS tensor components reveals that such a large 17O coordination shift is primarily due to the shielding increase along the direction that is within the O=C-O-Pt plane and perpendicular to the O-Pt bond. This result is interpreted as due to the σ donation from the oxygen nonbonding orbital (electron lone pair) to the Pt(II) empty dyz orbital, which results in large energy gaps between σ(Pt-O) and unoccupied molecular orbitals, thus reducing the paramagnetic shielding contribution along the direction perpendicular to the O-Pt bond. We found that the 17O QC tensor of the carboxylate oxygen is also sensitive to Pt(II) coordination, and that 17O CS and QC tensors provide complementary information about the O-Pt bonding. [ABSTRACT FROM AUTHOR]

Nitrate is a key component of synthetic fertilizers that can be beneficial to crop production in agro-ecosystems, but can also cause damage to natural ecosystems if it is exported in large amounts. Stable isotopes, both oxygen and nitrogen, have been used to trace the sources and fate of nitrate in various ecosystems. However, the oxygen isotope composition of synthetic and organic nitrates is poorly constrained. Here, we present a study on the N and O isotope composition of nitrate-based fertilizers. Theδ15N values of synthetic and natural nitrates were 0 ± 2 ‰ similar to the air N2from which they are derived. Theδ18O values of synthetic nitrates were 23 ± 3 ‰, similar to air O2, and natural nitrate fertilizerδ18O values (55 ± 5 ‰) were similar to those observed in atmospheric nitrate. The Δ17O values of synthetic fertilizer nitrate were approximately zero following a mass-dependent isotope relationship, while natural nitrate fertilizers had Δ17O values of 18 ± 2 ‰ similar to nitrate produced photochemically in the atmosphere. These narrow ranges of values can be used to assess the amount of nitrate arising from fertilizers in mixed systems where more than one nitrate source exists (soil, rivers, and lakes) using simple isotope mixing models. [ABSTRACT FROM AUTHOR]

The use of 17O enriched samples of alcohols to measure the correlation time of the OH internuclear vector works well when the hydroxyl proton exchanges rapidly. For alcohols such as methanol and ethanol the hydroxyl exchange rate for neat samples is relatively slow even at room temperature and significant systematic errors result if slow exchange effects are not considered. For slow exchange the hydroxyl proton, 17OH, signal is a relatively complex function of the chemical exchange rate of the hydroxyl proton, the OH spin coupling (about 80 Hz for alcohols and water) and the relaxation time for the oxygen. The OH linewidth can become so large due to scalar relaxation with the rapidly relaxing oxygen nucleus that the signal becomes very difficult to detect. For neat 17O enriched ethanol at room temperature the oxygen relaxation time is about 3.0 ms and the hydroxyl proton linewidth is over 1000 Hz.

Observation of Brønsted acid sites: By enhancing the solid‐state NMR signals of 17O at natural abundance with dynamic nuclear polarization (DNP), Pruski et al. were able to measure oxygen–proton distances accurately with sub‐picometer precision. The results give insight into the Brønsted acidity of a range of solid acid catalysts. [ABSTRACT FROM AUTHOR]

The second-order quadrupolar broadening of the central transition of nuclear probes with half-integer spins I is demonstrated to be useful to detect ultraslow molecular motions. On the basis of density matrix calculations explicit expressions are derived for quadrupolarly modulated sin–sin and cos–cos signals of selectively excited nuclei with I = 3/2, 5/2, 7/2, and 9/2. These correlation functions are suitable for implementation in two-dimensional exchange spectroscopy as well as for stimulated-echo experiments. As an application, 17 O measurements of the reorientational correlation function of water molecules in hexagonal ice are presented. [ABSTRACT FROM AUTHOR]

In principle, all nuclei with nonzero spin can be employed for magnetic resonance imaging (MRI). Special scanner hardware and MR sequences are required to select the nucleus-specific frequency and to enable imaging with 'sufficient' signal-to-noise ratio. This Special Issue starts with an overview of different nuclei that can be used for MRI today, followed by a review article about techniques required for imaging of quadrupolar nuclei with short relaxation times. Sequence developments to improve image quality and applications on different organs and diseases are presented for different nuclei (Na, Cl, O, and F), with a focus on imaging at natural abundance. [ABSTRACT FROM AUTHOR]

Purpose: To establish direct O-magnetic resonance imaging (MRI) for metabolic imaging at a clinical field strength of 3 T. Methods: An experimental setup including a surface coil and transmit/receive switch was constructed. Natural abundance in vivo brain images of a volunteer were acquired with a radial three-dimensional (3D) sequence in the visual cortex and in the heart with electrocardiogram (ECG)-gating. Results: In the brain, a signal-to-noise ratio of 36 was found at a nominal resolution of (5.6 mm), and a transverse relaxation time of T* = (1.9 ± 0.2) ms was obtained. In the heart O images were acquired with a temporal resolution of 200 ms. Conclusion: Cerebral and cardiac O-MRI at natural abundance is feasible at 3 T. [ABSTRACT FROM AUTHOR]

Industrial nitrogen (N) emissions in the Athabasca oil sands region (AOSR), Alberta, Canada, affect nitrate (NO3) and ammonium (NH4) deposition rates in close vicinity of industrial emitters. NO3–N and NH4–N open field and throughfall deposition rates were determined at various sites between 3 km and 113 km distance to the main oil sand operations between May 2008 and May 2009. NO3 and NH4 were analyzed for δ15N–NO3, δ18O–NO3, Δ17O–NO3 and δ15N–NH4. Marked differences in the δ18O and Δ17O values between industrial emissions and background deposition allowed for the estimation of minimum industrial contributions to atmospheric NO3 deposition. δ15N–NH4 values also allowed for estimates of industrial contributions to atmospheric NH4 deposition. Results revealed that particularly sites within ∼30 km radius from the main oil sands developments are significantly affected by industrial contributions to atmospheric NO3 and NH4 deposition. [Copyright &y& Elsevier]

Change in configuration and structure with composition are important components of thermodynamic and transport properties of most aluminosilicate melts, but the complex interactions, particularly in metaluminous and peraluminous compositions, are not yet well understood. In this paper, we present high-resolution 27Al and 17O MAS and 3QMAS NMR data on several calcium and potassium alumino silicate glasses prepared at several SiO2 isopleths, ranging from peralkaline to peraluminous compositions. In all calcium alumino silicate glasses, the VAl content increases with increasing Al content, while the NBO content decreases (in one series, below the limit of detection), consistent with other recent NMR studies of calcium alumino silicate glasses. An increase in VAl content per total Al is also observed as the glass approaches the calcia-silica binary. In the potassium aluminosilicate glasses, NBO is directly quantified for the first time in metaluminous and peraluminous compositions; VAl is below the detection limit. We discuss possible mechanisms for the incorporation of alumina into the melt structure and show how changes in the VAl content as a function of composition may be used to eliminate mechanisms that do not fit the observed data. We also explore reactions, which show the difficulty of explaining the NBO present on the metaluminous join with only the observed VAl, implying the necessity of multiple reactions producing NBO in such compositions. [ABSTRACT FROM AUTHOR]