| 1. |
- Cordova, M., et al.
(författare)
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Atomic-level structure determination of amorphous molecular solids by NMR
- 2023
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Ingår i: Nature Communications. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Structure determination of amorphous materials remains challenging, owing to the disorder inherent to these materials. Nuclear magnetic resonance (NMR) powder crystallography is a powerful method to determine the structure of molecular solids, but disorder leads to a high degree of overlap between measured signals, and prevents the unambiguous identification of a single modeled periodic structure as representative of the whole material. Here, we determine the atomic-level ensemble structure of the amorphous form of the drug AZD4625 by combining solid-state NMR experiments with molecular dynamics (MD) simulations and machine-learned chemical shifts. By considering the combined shifts of all 1H and 13C atomic sites in the molecule, we determine the structure of the amorphous form by identifying an ensemble of local molecular environments that are in agreement with experiment. We then extract and analyze preferred conformations and intermolecular interactions in the amorphous sample in terms of the stabilization of the amorphous form of the drug.
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| 2. |
- Quétel, C. R., et al.
(författare)
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Methylmercury in tuna: demonstrating measurement capabilities and evaluating comparability of results worldwide from the CCQM P-39 comparison
- 2005
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 20, s. 1058-66
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Tidskriftsartikel (refereegranskat)abstract
- Six metrology institutes (NMIs) representing at the Comité International des Poids et Mesures (CIPM) 4 Member States of the Metre Convention and 2 international organisations, and 8 expert laboratories selected outside CIPM have compared their capabilities to quantitatively measure methylmercury (MeHg) in a prepared tuna material containing approximately 4.3 mg kg–1 Hg. This comparison was the object of the CIPM–Comité Consultatif pour la Quantité de Matière (CCQM) Pilot Study 39, organised by the Institute for Reference Materials and Measurements (IRMM), from the European Commission—Joint Research Centre. Beside the test material itself, a bottle of the BCR-464 tuna Certified Reference Material (CRM) and an ampoule of IRMM-670, a 202Hg isotope enriched MeHg candidate isotopic CRM, were distributed to all participants, who were free to apply the measurement strategy of their choice. Four, including 1 NMI, relied on external calibration or the method of standard additions, whereas the other 10 implemented an isotope dilution mass spectrometry (IDMS) approach and chose to use the IRMM-670 for their measurements. Alkaline digestion at room temperature (with manual shaking) or high temperature (under sonication, oven or hot plate conditions) was employed by most participants, with hydrochloric acid leaching the second most popular choice. Alkylation (4 phenylations, 4 ethylations and 3 propylations) in the aqueous phase was preferred by a large majority over butylation by the Grignard reaction. All participants were requested to estimate the uncertainty associated with their results and 9 out of 14 stated relative combined uncertainties below 6%(k= 2). Despite this apparent consensus, the perception of which factor caused the largest contribution to this estimation differed among participants because of the differences in the analytical methodologies deployed but also because of wide differences of the concepts of uncertainty estimation. The mixture mode(MM) median, calculated also from the measurement uncertainties stated by the participants, was 1.967 ± 0.204 × 10–5 mol kg–1(95% confidence). Twelve of the results were re-grouped within a range of less than 0.3 × 10–5 mol kg–1(MM median = 1.967 ± 0.162 × 10–5 mol kg–1, 95% confidence): they nearly all (1 exception) overlapped with each other within k= 2 stated uncertainties. For the other 2 results the uncertainty seemed to have been particularly underestimated as they lay, respectively, at more than 20% above and less than –40% below the overall average. The relative standard deviation of the results of 9 laboratories out of the 10 that applied IDMS was about 2.6%. It can be assumed from the degree of equivalence shown by 12 out of 14 study participants that, at present, laboratories worldwide are potentially able to supply accurate results for MeHg in fish-type matrices (containing about 2 × 10–5 mol kg–1) within ±10% uncertainty. This encouraging outcome permitted scheduling of a follow-up CCQM-K43 key comparison for a lower MeHg content level in salmon tissues.
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| 3. |
- Bennett, Deborah, et al.
(författare)
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Project TENDR : Targeting Environmental Neuro-Developmental Risks. The TENDR Consensus Statement
- 2016
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Ingår i: Journal of Environmental Health Perspectives. - : National Institute of Environmental Health Science. - 0091-6765 .- 1552-9924. ; 124:7, s. A118-A122
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Tidskriftsartikel (refereegranskat)abstract
- Children in America today are at an unacceptably high risk of developing neurodevelopmental disorders that affect the brain and nervous system including autism, attention deficit hyperactivity disorder, intellectual disabilities, and other learning and behavioral disabilities. These are complex disorders with multiple causes-genetic, social, and environmental. The contribution of toxic chemicals to these disorders can be prevented. Approach: Leading scientific and medical experts, along with children's health advocates, came together in 2015 under the auspices of Project TENDR: Targeting Environmental Neuro-Developmental Risks to issue a call to action to reduce widespread exposures to chemicals that interfere with fetal and children's brain development. Based on the available scientific evidence, the TENDR authors have identified prime examples of toxic chemicals and pollutants that increase children's risks for neurodevelopmental disorders. These include chemicals that are used extensively in consumer products and that have become widespread in the environment. Some are chemicals to which children and pregnant women are regularly exposed, and they are detected in the bodies of virtually all Americans in national surveys conducted by the U.S. Centers for Disease Control and Prevention. The vast majority of chemicals in industrial and consumer products undergo almost no testing for developmental neurotoxicity or other health effects. Conclusion: Based on these findings, we assert that the current system in the United States for evaluating scientific evidence and making health-based decisions about environmental chemicals is fundamentally broken. To help reduce the unacceptably high prevalence of neurodevelopmental disorders in our children, we must eliminate or significantly reduce exposures to chemicals that contribute to these conditions. We must adopt a new framework for assessing chemicals that have the potential to disrupt brain development and prevent the use of those that may pose a risk. This consensus statement lays the foundation for developing recommendations to monitor, assess, and reduce exposures to neurotoxic chemicals. These measures are urgently needed if we are to protect healthy brain development so that current and future generations can reach their fullest potential.
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| 4. |
- Boissier, Catherine, 1972, et al.
(författare)
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Water-based latex dispersions: 4. Exchange dynamics and residence times of nonylphenol ethoxylate in concentrated latex dispersions
- 2005
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 292:1, s. 63-70
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium residence times of the nonionic surfactant nonylphenol ethoxylate (NP100) in a latex dispersion were determined using NMR diffusometry. At 16% w/w particle concentration and 0.12, 0.43 and 0.81% w/w NP100, the residence times of the surfactant were 0.16, 1.02 and 4.73 s in solution (τA) and 0.3, 0.37 and 0.61 s on the surface of the particles (τB), respectively. At even higher particle concentration (>45% w/w), τA and τB were 1.47 and 2.2 s. Calculating the number of collisions that ought to result in adsorbed species, at 16% w/w, only 2, 5 and 2‰ (corresponding to 0.12, 0.43 and 0.81% w/w NP100) resulted in adsorption, whereas at >45% w/w, only 12‰ resulted in adsorption, which suggested that the surfactant was irreversibly adsorbed on the particles. The small increase in collision frequency with increased particle concentration could be a result of a diffusion controlled adsorption, while an energy barrier for desorption controlled the overall exchange dynamics in the dispersion. The slow dynamics in the dispersion was controlled, mainly by the nonylphenol group, which gave NP100 a strong preference to surfaces. In addition, the chain length of the poly(ethylene glycol) (PEG) group changed the solution behavior from being that of a typical surfactant to that of a polymer.
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| 5. |
- Eklind, H, et al.
(författare)
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Characterization of the interphase in PPO/PMMA blends compatibilized by P(S-g-EO)
- 1996
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 29:3, s. 984-992
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Tidskriftsartikel (refereegranskat)abstract
- The influence of a poly(styrene-graft-ethylene oxide) (P(S-g-EO)) copolymer on poly(2,6-dimethyl-p-phenylene oxide)/poly(methyl methacrylate) (PPO/PMMA) blends was studied by a number of different techniques in order to characterize the properties of the interphase. Scanning electron microscopy shows that the copolymer reduces the dispersed phase size, and dynamic mechanical spectroscopy (DMS) reveals a new micromechanical transition in the ternary blends. These effects are shown to be caused by a copolymer-rich interphase with a certain volume fraction and with its own characteristic properties. Solid-state nuclear magnetic resonance (NMR) relaxation times indicate that the poly(ethylene oxide) side chains of the copolymer are partially miscible with PMMA in the ternary blends, which suggests that the interphase does not only consist of pure copolymer.
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| 6. |
- Erlinge, S, et al.
(författare)
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Predation on brown hare and ring-necked pheasant populations on southern Sweden
- 1984
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Ingår i: Holarctic Ecology. ; 7:3, s. 300-304
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Tidskriftsartikel (refereegranskat)abstract
- in an open field area in southern Sweden. Biomass and numbers of hares and pheasants eaten by the predators were calculated from data on food habits, food requirements, and numbers of the mammalian and avian predators present (11 species). At the same time estimates of numbers and production of hares and pheasants were obtained. At least 40% of the estimated annual production of hares and almost 60% of subadult-adultp heasants in autumn were consumed by the predators. Estimated numbers of hares and pheasants taken by the predators greatly exceeded shootinga nd road mortality.F oxes and cats were the predominantp reda-tors on hares( about9 0%o f total harec onsumption). Foxesa ccountedf or aboutt wo-thirds of predation on pheasants; cats and goshawks were of secondary importance. Pheasant nests were preyed upon by hooded crows and also by badgers. Hares and pheasantsc ontributedo nly about 3 and 1%, respectively,o f the food of the predators.
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| 7. |
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| 8. |
- Karlsson, Stina, 1975, et al.
(författare)
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Characterization and mathematical modelling of single fluidised particle coating
- 2011
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 207:1-3, s. 245-256
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Tidskriftsartikel (refereegranskat)abstract
- A study was made of coating single particles with water-based dispersions under realistic fluid dynamic and well-defined operating conditions. The surfaces of the coated particles were observed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM was used to study the latex particle packing and the colloid particle coalescence at the nanoscale, while SEM was used to study the film at the droplet size level. The influence of temperature, moisture content and spray rate were investigated. The experiments showed a coating layer built up of rings of colloid particles for all cases studied except for high spray rate. A variation in the degree of coalescence between colloid particles with different glass transition temperatures, T-g, was shown in AFM. Cracks in the coating layer were observed when the temperature was lower than T-g. Mechanism evaluation using dimensionless numbers showed that a droplet will spread to the equilibrium angle without splashing; the colloid particles accumulate at the interface between the liquid and the air for all cases studied except air with 90% RH and 20 degrees C and a wet-bulb temperature in the coating layer. The evaluation indicated that no skin forms in any of the cases. A model of the drying of a single droplet was developed to describe the experimental results with rings of colloid particles. The simulation of the shape and height of the dried droplet agrees well with the experimental results. (C) 2010 Elsevier B.V. All rights reserved.
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| 9. |
- Ohlin, Mats, et al.
(författare)
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Crystallization, neutron data collection, initial structure refinement and analysis of a xyloglucan heptamer bound to an engineered carbohydrate-binding module from xylanase.
- 2015
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Ingår i: Acta crystallographica. Section F, Structural biology communications. - 2053-230X. ; 71:Pt 8, s. 1072-1077
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Tidskriftsartikel (refereegranskat)abstract
- Carbohydrate-binding modules (CBMs) are discrete parts of carbohydrate-hydrolyzing enzymes that bind specific types of carbohydrates. Ultra high-resolution X-ray crystallographic studies of CBMs have helped to decipher the basis for specificity in carbohydrate-protein interactions. However, additional studies are needed to better understand which structural determinants confer which carbohydrate-binding properties. To address these issues, neutron crystallographic studies were initiated on one experimentally engineered CBM derived from a xylanase, X-2 L110F, a protein that is able to bind several different plant carbohydrates such as xylan, β-glucan and xyloglucan. This protein evolved from a CBM present in xylanase Xyn10A of Rhodothermus marinus. The protein was complexed with a branched xyloglucan heptasaccharide. Large single crystals of hydrogenous protein (∼1.6 mm(3)) were grown at room temperature and subjected to H/D exchange. Both neutron and X-ray diffraction data sets were collected to 1.6 Å resolution. Joint neutron and X-ray refinement using phenix.refine showed significant density for residues involved in carbohydrate binding and revealed the details of a hydrogen-bonded water network around the binding site. This is the first report of a neutron structure of a CBM and will add to the understanding of protein-carbohydrate binding interactions.
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| 10. |
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