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https://www.readbyqxmd.com/read/28230987/urinary-antibiotics-of-pregnant-women-in-eastern-china-and-cumulative-health-risk-assessment
#1
Hexing Wang, Na Wang, Junhua Qian, Lingyun Hu, Peixin Huang, Meifang Su, Xin Yu, Chaowei Fu, Feng Jiang, Qi Zhao, Ying Zhou, Haijiang Lin, Gengsheng He, Yue Chen, Qingwu Jiang
Exposure to antibiotics during pregnancy can pose a systematic effect on human health. A few bio-monitoring studies have demonstrated an extensive exposure of children to antibiotics, but there is still lack of data for pregnant women. To assess the exposure of pregnant women to antibiotics and potential health risk, we investigated 536 pregnant women aged 16-42 years from two geographically different study sites in Eastern China in 2015. We measured 21 antibiotics of five categories (seven fluoroquinolones, three phenicols, four tetracyclines, three macrolides, and four sulfonamides) in urines by using the isotope dilution ultra-performance liquid chromatography coupled to quadrupole time of-flight mass spectrometry...
February 23, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28230896/using-carbon-oxygen-strontium-and-lead-isotopes-in-modern-human-teeth-for-forensic-investigations-a-critical-overview-based-on-data-from-bulgaria
#2
George D Kamenov, Jason H Curtis
Isotopic data obtained from human remains can provide information about an individual's origin, migration, and diet. We evaluate the usefulness of carbon, oxygen, strontium, and lead isotopes for forensic investigations by comparing data from Bulgarian teeth with data from other regions. Geo-referencing based on oxygen or strontium isotopes can be misleading due to overlap with other countries in Europe and other continents. Carbon and lead isotopes, in combination with oxygen and strontium isotopes, provide the most useful information for identification of local vs foreigner status...
February 23, 2017: Journal of Forensic Sciences
https://www.readbyqxmd.com/read/28230781/-dose-to-mother-deuterium-oxide-dilution-technique-an-accurate-strategy-to-measure-vitamin-a-intake-in-breastfed-infants
#3
Veronica Lopez-Teros, Ana Teresa Limon-Miro, Humberto Astiazaran-Garcia, Sherry A Tanumihardjo, Orlando Tortoledo-Ortiz, Mauro E Valencia
In Mexico, infants (0-2 years old) show the highest prevalence of vitamin A deficiency (VAD), measured by serum retinol concentrations. Thus, we consider that low vitamin A (VA) intake through breast milk (BM) combined with poor weaning practices are the main factors that contribute to VAD in this group. We combined the assessment of VA status in lactating women using BM retinol and a stable isotope 'dose-to-mother' technique to measure BM production in women from urban and agricultural areas. Infants' mean BM intake was 758 ± 185 mL, and no difference was observed between both areas (p = 0...
February 21, 2017: Nutrients
https://www.readbyqxmd.com/read/28230765/metabolic-effects-of-glucose-fructose-co-ingestion-compared-to-glucose-alone-during-exercise-in-type-1-diabetes
#4
Lia Bally, Patrick Kempf, Thomas Zueger, Christian Speck, Nicola Pasi, Carlos Ciller, Katrin Feller, Hannah Loher, Robin Rosset, Matthias Wilhelm, Chris Boesch, Tania Buehler, Ayse S Dokumaci, Luc Tappy, Christoph Stettler
This paper aims to compare the metabolic effects of glucose-fructose co-ingestion (GLUFRU) with glucose alone (GLU) in exercising individuals with type 1 diabetes mellitus. Fifteen male individuals with type 1 diabetes (HbA1c 7.0% ± 0.6% (53 ± 7 mmol/mol)) underwent a 90 min iso-energetic continuous cycling session at 50% VO2max while ingesting combined glucose-fructose (GLUFRU) or glucose alone (GLU) to maintain stable glycaemia without insulin adjustment. GLUFRU and GLU were labelled with (13)C-fructose and (13)C-glucose, respectively...
February 21, 2017: Nutrients
https://www.readbyqxmd.com/read/28230365/catalytic-enantioselective-2-3-rearrangements-of-allylic-ammonium-ylides-a-mechanistic-and-computational-study
#5
Thomas H West, Daniel M Walden, James E Taylor, Alexander C Brueckner, Ryne C Johnston, Paul H-Y Cheong, Guy C Lloyd-Jones, Andrew D Smith
A mechanistic study of the isothiourea-catalysed enantioselective [2,3]-rearrangement of allylic ammonium ylides is described. Reaction kinetic analyses using 19F NMR and density functional theory computations have elucidated a reaction profile and allowed identification of the catalyst resting state and turnover-rate limiting step. A catalytically-rele- vant catalyst-substrate adduct has been observed, and its constitution elucidated unambiguously by 13C and 15N isotopic labelling. Isotopic entrainment has shown the observed catalyst-substrate adduct to be a genuine intermediate on the pro- ductive cycle towards catalysis...
February 23, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28230101/a-novel-role-for-methyl-cysteinate-a-cysteine-derivative-in-cesium-accumulation-in-arabidopsis-thaliana
#6
Eri Adams, Takae Miyazaki, Aya Hayaishi-Satoh, Minwoo Han, Miyako Kusano, Himanshu Khandelia, Kazuki Saito, Ryoung Shin
Phytoaccumulation is a technique to extract metals from soil utilising ability of plants. Cesium is a valuable metal while radioactive isotopes of cesium can be hazardous. In order to establish a more efficient phytoaccumulation system, small molecules which promote plants to accumulate cesium were investigated. Through chemical library screening, 14 chemicals were isolated as 'cesium accumulators' in Arabidopsis thaliana. Of those, methyl cysteinate, a derivative of cysteine, was found to function within the plant to accumulate externally supplemented cesium...
February 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28229340/theoretical-calculation-of-polarizability-isotope-effects
#7
Félix Moncada, Roberto Flores-Moreno, Andrés Reyes
We propose a scheme to estimate hydrogen isotope effects on molecular polarizabilities. This approach combines the any-particle molecular orbital method, in which both electrons and H/D nuclei are described as quantum waves, with the auxiliary density perturbation theory, to calculate analytically the polarizability tensor. We assess the performance of method by calculating the polarizability isotope effect for 20 molecules. A good correlation between theoretical and experimental data is found. Further analysis of the results reveals that the change in the polarizability of a X-H bond upon deuteration decreases as the electronegativity of X increases...
March 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28228627/orthodontic-archwire-composition-and-phase-analyses-by-neutron-spectroscopy
#8
Kun V Tian, Giulia Festa, Francesco Basoli, Giuseppina Laganà, Antonella Scherillo, Carla Andreani, Patrizio Bollero, Silvia Licoccia, Roberto Senesi, Paola Cozza
Quantitative metallurgical and phase analyses employing neutron diffraction technique were conducted on two as-received commercial rectangular austenitic stainless steel orthodontic archwires, G&H and Azdent, 0.43×0.64 mm (0.017×0.025 inch). Results showed a bi-phase structure containing martensitic phase (45.67% for G&H and 6.62% for Azdent) in addition to the expected metastable austenite. The former may be a strain-induced phase-transformation arising during the cold working process of wire fabrication...
February 22, 2017: Dental Materials Journal
https://www.readbyqxmd.com/read/28228237/groundwater-nitrate-reduction-versus-dissolved-gas-production-a-tale-of-two-catchments
#9
E B McAleer, C E Coxon, K G Richards, M M R Jahangir, J Grant, Per E Mellander
At the catchment scale, a complex mosaic of environmental, hydrogeological and physicochemical characteristics combine to regulate the distribution of groundwater and stream nitrate (NO3(-)). The efficiency of NO3(-) removal (via denitrification) versus the ratio of accumulated reaction products, dinitrogen (excess N2) & nitrous oxide (N2O), remains poorly understood. Groundwater was investigated in two well drained agricultural catchments (10km(2)) in Ireland with contrasting subsurface lithologies (sandstone vs...
February 19, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28228167/atomic-scale-analytical-tomography
#10
Thomas F Kelly
The concept of atomic-scale tomography has been proposed in the past decade as a technique that could deliver the position of all atoms with high precision and their elemental (isotopic) identity. The technique was never intended to be limited to merely structural information and there is clearly a rich array of additional analytical information that can be brought to bear on such tomographs. In this paper, some of these types of information are considered and the implications are explored. The fuller realm of this analytical and structural information may be called atomic-scale analytical tomography...
February 2017: Microscopy and Microanalysis
https://www.readbyqxmd.com/read/28228011/spectroscopic-definition-of-the-cuz-o-intermediate-in-turnover-of-nitrous-oxide-reductase-and-molecular-insight-into-the-catalytic-mechanism
#11
Esther M Johnston, Cíntia Carreira, Simone Dell'Acqua, Somdatta Ghosh Dey, Sofia R Pauleta, Isabel Moura, Edward I Solomon
Spectroscopic methods and density functional theory (DFT) calculations are used to determine the geometric and electronic structure of CuZ(o), an intermediate form of the Cu4S active site of nitrous oxide reductase (N2OR) that is observed in single turnover of fully reduced N2OR with N2O. Electron paramagnetic resonance (EPR), absorption, and magnetic circular dichroism (MCD) spectroscopies show that CuZ(o) is a 1-hole (i.e. 3Cu(I)Cu(II)) state with spin density delocalized evenly over CuI and CuIV. Resonance Raman spectroscopy shows two Cu-S vibrations at 425 and 413 cm(-1), the latter with a -3 cm(-1) O(18) solvent isotope shift...
February 22, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28225829/inhibition-of-arabidopsis-chloroplast-%C3%AE-amylase-bam3-by-maltotriose-suggests-a-mechanism-for-the-control-of-transitory-leaf-starch-mobilisation
#12
Jing Li, Wenxu Zhou, Perigio Francisco, Russell Wong, Dongke Zhang, Steven M Smith
Starch breakdown in leaves at night is tightly matched to the duration of the dark period, but the mechanism by which this regulation is achieved is unknown. In Arabidopsis chloroplasts, β-amylase BAM3 hydrolyses transitory starch, producing maltose and residual maltotriose. The aim of the current research was to investigate the regulatory and kinetic properties of BAM3. The BAM3 protein was expressed in Escherichia coli and first assayed using a model substrate. Enzyme activity was stimulated by treatment with dithiothreitol and was increased 40% by 2-10 μM Ca2+ but did not require Mg2+...
2017: PloS One
https://www.readbyqxmd.com/read/28225599/cubic-sr2scgao5-perovskite-structural-stability-oxygen-defect-structure-and-ion-conductivity-explored-on-single-crystals
#13
Serena Corallini, Monica Ceretti, Alain Cousson, Clemens Ritter, Marco Longhin, Philippe Papet, Werner Paulus
Oxygen-deficient Sr2ScGaO5 single crystals with a cubic perovskite structure were grown by the floating-zone technique. The transparent crystals of this pure 3D oxygen electrolyte are metastable at ambient temperature, showing one-sixth of all oxygen positions vacant. While neutron single-crystal diffraction, followed by maximum entropy analysis, revealed a strong anharmonic displacements for the oxygen atoms, a predominant formation of ScO6 octahedra and GaO4 tetrahedra is indicated by Raman spectroscopic studies, resulting in a complex oxygen defect structure with short-range order...
February 22, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28225594/mass-spectral-feature-list-optimizer-ms-flo-a-tool-to-minimize-false-positive-peak-reports-in-untargeted-lc-ms-data-processing
#14
Brian C Defelice, Sajjan Singh Mehta, Stephanie Samra, Tomas Cajka, Benjamin Wancewicz, Johannes F Fahrmann, Oliver Fiehn
Untargeted metabolomics by liquid chromatography-mass spectrometry generates data rich chromatograms in form of m/z-retention time features. Managing such datasets is a bottleneck. Many popular data processing tools, including XCMS-online and MZmine2, yield numerous false positive peak detections. Flagging and removing such false peaks manually is a time consuming task and prone to human error. We present a web application, MS Feature List Optimizer (MS-FLO), to improve the quality of feature lists after initial processing to expedite the process of data curation...
February 22, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28225553/correlations-among-mercury-concentration-and-stable-isotope-ratios-of-carbon-and-nitrogen-of-amino-acids-in-scalp-hair-from-whale-meat-eaters-and-heavy-fish-eaters
#15
Tetsuya Endo, Hideki Ogasawara, Moriaki Hayasaka, Yohei Hotta, Osamu Kimura, Klaus J Petzke
RATIONALE: As Hg accumulation in marine animals generally increases with increased trophic level (δ(15) N values) through the food web, predators accumulate higher levels of Hg. The main source of human Hg intake is the consumption of fish and other marine animals, and Hg concentration in scalp hair is the preferred marker for evaluating consumption of marine animals. Difference of δ(15) N values between trophic and source amino acids of human consumers could enable us to estimate the trophic level of consumer without knowing the bulk δ(15) N value of their prey...
February 22, 2017: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/28224993/dynamical-barrier-and-isotope-effects-in-the-simplest-substitution-reaction-via-walden-inversion-mechanism
#16
Zhiqiang Zhao, Zhaojun Zhang, Shu Liu, Dong H Zhang
Reactions occurring at a carbon atom through the Walden inversion mechanism are one of the most important and useful classes of reactions in chemistry. Here we report an accurate theoretical study of the simplest reaction of that type: the H+CH4 substitution reaction and its isotope analogues. It is found that the reaction threshold versus collision energy is considerably higher than the barrier height. The reaction exhibits a strong normal secondary isotope effect on the cross-sections measured above the reaction threshold, and a small but reverse secondary kinetic isotope effect at room temperature...
February 22, 2017: Nature Communications
https://www.readbyqxmd.com/read/28224987/towards-high-resolution-laser-ionization-spectroscopy-of-the-heaviest-elements-in-supersonic-gas-jet-expansion
#17
R Ferrer, A Barzakh, B Bastin, R Beerwerth, M Block, P Creemers, H Grawe, R de Groote, P Delahaye, X Fléchard, S Franchoo, S Fritzsche, L P Gaffney, L Ghys, W Gins, C Granados, R Heinke, L Hijazi, M Huyse, T Kron, Yu Kudryavtsev, M Laatiaoui, N Lecesne, M Loiselet, F Lutton, I D Moore, Y Martínez, E Mogilevskiy, P Naubereit, J Piot, S Raeder, S Rothe, H Savajols, S Sels, V Sonnenschein, J-C Thomas, E Traykov, C Van Beveren, P Van den Bergh, P Van Duppen, K Wendt, A Zadvornaya
Resonant laser ionization and spectroscopy are widely used techniques at radioactive ion beam facilities to produce pure beams of exotic nuclei and measure the shape, size, spin and electromagnetic multipole moments of these nuclei. However, in such measurements it is difficult to combine a high efficiency with a high spectral resolution. Here we demonstrate the on-line application of atomic laser ionization spectroscopy in a supersonic gas jet, a technique suited for high-precision studies of the ground- and isomeric-state properties of nuclei located at the extremes of stability...
February 22, 2017: Nature Communications
https://www.readbyqxmd.com/read/28224912/high-throughput-screening-and-quantitation-of-guanidino-and-ureido-compounds-using-liquid-chromatography-drift-tube-ion-mobility-spectrometry-mass-spectrometry
#18
Ruo-Jing Fan, Fang Zhang, Xiu-Ping Chen, Wan-Shu Qi, Qing Guan, Tuan-Qi Sun, Yin-Long Guo
The present work focused on the high-throughput screening and quantitation of guanidino compounds (GCs) and ureido compounds (UCs) in human thyroid tissues. The strategy employed benzylic rearrangement stable isotope labeling (BRSIL) for the sample preparation and then detection using liquid chromatography-drift tube ion mobility spectrometry-quadrupole time of flight mass spectrometry (LC-DTIMS-QTOF MS). A short reversed-phase LC realized an on-line desalting and a measurement cycle of 5.0 min. DTIMS separation enhanced the better specificity and selectivity for the benzil labeled GCs and UCs...
April 8, 2017: Analytica Chimica Acta
https://www.readbyqxmd.com/read/28224911/determination-of-total-cyanide-in-soil-by-isotope-dilution-gc-ms-following-pentafluorobenzyl-derivatization
#19
Beatrice Campanella, Lorenzo Biancalana, Lucia D'Ulivo, Massimo Onor, Emilia Bramanti, Zoltan Mester, Enea Pagliano
The high toxicity of cyanide, along with its widespread industrial use, has fuelled interest in the development of analytical methods for its determination in complex matrices. In this study, we propose a novel approach for the measurement of total cyanide in soil samples based on single-step derivatization with pentafluorobenzyl bromide (F5Bn-Br) followed by quantitation with gas chromatography mass spectrometry in negative chemical ionization mode. The reaction between CN(-) and F5Bn-Br resulted in the identification of several derivatives such as F5Bn-CN, (F5Bn)(F5Ph)CH-CN, and (F5Bn)2(F5Ph)C-CN...
April 8, 2017: Analytica Chimica Acta
https://www.readbyqxmd.com/read/28224906/a-comparative-study-of-sample-dissolution-techniques-and-plasma-based-instruments-for-the-precise-and-accurate-quantification-of-rees-in-mineral-matrices
#20
Laurence Whitty-Léveillé, Keven Turgeon, Claude Bazin, Dominic Larivière
The recent commercialisation of inductively coupled plasma tandem mass spectrometric (ICP-MS/MS) instruments has provided analytical chemists with a new tool to properly quantify atomic composition in a variety of matrices with minimal sample preparation. In this article, we report on our assessment of the compatibility of 3 sample preparation techniques (open-vessel acid digestion, microwave digestion and alkaline fusion) for the quantification of rare earth elements (REEs) in mineral matrices. The combination of the high digestion temperatures (1050 °C) and using LiBO2 as a flux was the most effective strategy for the digestion of all rare earth elements in mineral matrices and was compatible with ICP-MS/MS measurements...
April 8, 2017: Analytica Chimica Acta
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