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https://www.readbyqxmd.com/read/29332280/hydrogeochemical-processes-and-influence-of-seawater-intrusion-in-coastal-aquifers-south-of-chennai-tamil-nadu-india
#1
G Kanagaraj, L Elango, S G D Sridhar, G Gowrisankar
Seawater intrusion promotes the salinity of groundwater, and it poses a great environmental impact on a global scale. The present study was carried out to determine the hydrogeochemical processes and influence of seawater intrusion in the coastal aquifers using geophysical, geochemical, and stable isotope techniques. The true resistivity value ranges from 0.5 to 8008.5 Ω-m which has been measured using vertical electrical sounding (VES) based on the Schlumberger method. About 33 groundwater samples were collected during post-monsoon (POM) (January 2012) and pre-monsoon (PRM) (June 2012) seasons from open and bore wells and were analyzed for major ions and stable isotopes...
January 14, 2018: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/29331769/source-identification-of-uranium-containing-materials-at-mine-legacy-sites-in-portugal
#2
A C Keatley, P G Martin, K R Hallam, O D Payton, R Awbery, F Carvalho, J M Oliveira, L Silva, M Malta, T B Scott
Whilst prior nuclear forensic studies have focused on identifying signatures to distinguish between different uranium deposit types, this paper focuses on providing a scientific basis for source identification of materials from different uranium mine sites within a single region, which can then be potentially used within nuclear forensics. A number of different tools, including gamma spectrometry, alpha spectrometry, mineralogy and major and minor elemental analysis, have been utilised to determine the provenance of uranium mineral samples collected at eight mine sites, located within three different uranium provinces, in Portugal...
January 10, 2018: Journal of Environmental Radioactivity
https://www.readbyqxmd.com/read/29330778/isotopic-exchange-hplc-hrms-ms-applied-to-cyclic-proanthocyanidins-in-wine-and-cranberries
#3
Edoardo Longo, Fabrizio Rossetti, Matteo Scampicchio, Emanuele Boselli
Cyclic B-type proanthocyanidins in red wines and grapes have been discovered recently. However, proanthocyanidins of a different chemical structure (non-cyclic A-type proanthocyanidins) already known to be present in cranberries and wine possess an identical theoretical mass. As a matter of fact, the retention times and the MS/MS fragmentations found for the proposed novel cyclic B-type tetrameric proanthocyanidin in red wine and the known tetrameric proanthocyanidin in a cranberry extract are herein shown to be identical...
January 12, 2018: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/29330535/the-stoichiometry-of-coral-dinoflagellate-symbiosis-carbon-and-nitrogen-cycles-are-balanced-in-the-recycling-and-double-translocation-system
#4
Yasuaki Tanaka, Atsushi Suzuki, Kazuhiko Sakai
Symbioses between microalgae and animal hosts have the advantage of acquiring and sharing autotrophically produced organic carbon (C) as their energy source. However, the stoichiometry and turnover rates of biological elements in symbioses are not fully understood because of complicated metabolic interactions. We report the first comprehensive and simultaneous measurement of C and nitrogen (N) flows through coral-dinoflagellate symbiosis by using the unique approach of dual-isotope labeling with 13C and 15N, in situ chasing, and isotope-mixing models...
January 12, 2018: ISME Journal
https://www.readbyqxmd.com/read/29330518/spartina-alterniflora-invasion-affects-soil-carbon-in-a-c3-plant-dominated-tidal-marsh
#5
Min Wang, Qing Wang, Chenyan Sha, Jiakuan Chen
The carbon cycle is significantly affected by Spartina alterniflora invasion through its impact on blue carbon in many salt marshes. To determine the impacts on soil organic carbon (SOC), we studied the vertical and horizontal distribution of SOC. And stable carbon isotopes were used to explore the impact of the age of S. alterniflora invasion on SOC in Chongming Dongtan wetland located in the Yangtze River estuary, China. The results showed that the SOC concentration was higher in the S. alterniflora community than that in the native Phragmites australis community...
January 12, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29329228/current-nmr-techniques-for-structure-based-drug-discovery
#6
REVIEW
Toshihiko Sugiki, Kyoko Furuita, Toshimichi Fujiwara, Chojiro Kojima
A variety of nuclear magnetic resonance (NMR) applications have been developed for structure-based drug discovery (SBDD). NMR provides many advantages over other methods, such as the ability to directly observe chemical compounds and target biomolecules, and to be used for ligand-based and protein-based approaches. NMR can also provide important information about the interactions in a protein-ligand complex, such as structure, dynamics, and affinity, even when the interaction is too weak to be detected by ELISA or fluorescence resonance energy transfer (FRET)-based high-throughput screening (HTS) or to be crystalized...
January 12, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29329084/sources-of-polychlorinated-dibenzo-p-dioxins-and-dibenzofurans-and-biphenyls-in-chinese-mitten-crabs
#7
Ying Han, Wenbin Liu, Wen Zhu, Kaifeng Rao, Ke Xiao, Lirong Gao, Guijin Su, Guorui Liu
Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in Chinese mitten crabs from several areas were determined. The toxic equivalents (TEQs) for the mean PCDD/F and total PCDD/F and dioxin-like PCBs were 2.9 ± 2.7 and 5.7 ± 4.0 pg TEQ g-1, respectively. The mean concentrations of PCBs and dl-PCBs were 282 and 59 times the concentrations of PCDD/Fs, respectively. PCDD/F and PCB sources in the crab food web were assessed. The total TEQ of PCDD/F and PCB supplied by crab compound feed was 2...
January 6, 2018: Chemosphere
https://www.readbyqxmd.com/read/29328712/recoil-effect-on-the-g-factor-of-li-like-ions
#8
V M Shabaev, D A Glazov, A V Malyshev, I I Tupitsyn
The nuclear recoil effect on the g factor of Li-like ions is evaluated. The one-electron recoil contribution is treated within the framework of the rigorous QED approach to the first order in the electron-to-nucleus mass ratio m/M and to all orders in the parameter αZ. These calculations are performed in a range Z=3-92. The two-electron recoil term is calculated for low- and middle-Z ions within the Breit approximation using a four-component approach. The results for the two-electron recoil part obtained in the Letter strongly disagree with the previous calculations performed using an effective two-component Hamiltonian...
December 29, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29328674/new-insights-on-ecosystem-mercury-cycling-revealed-by-stable-isotopes-of-mercury-in-water-flowing-from-a-headwater-peatland-catchment
#9
Glenn Woerndle, Martin Tsz-Ki Tsui, Stephen Sebestyen, Joel D Blum, Xiangping Nie, Randall K Kolka
Stable isotope compositions of mercury (Hg) were measured in the outlet stream and in soil cores at different landscape positions in a 9.7-ha boreal upland-peatland catchment in northern Minnesota. An acidic permanganate/persulfate digestion procedure was validated for water samples with high dissolved organic matter (DOM) concentrations and we verified the complete breakdown of DOM through Hg spike addition analysis. We report a relatively large variation in mass-dependent fractionation (δ202Hg; from -2.12 to -1...
January 12, 2018: Environmental Science & Technology
https://www.readbyqxmd.com/read/29328626/polystyrene-core-silica-shell-scintillant-nanoparticles-for-low-energy-radionuclide-quantification-in-aqueous-media
#10
Colleen M Janczak, Isen A C Calderon, Zeinab Mokhtari, Craig Alan Aspinwall
β-particle emitting radionuclides are useful molecular labels due to their abundance in biomolecules. Detection of -emission from 3H, 35S, and 33P, important biological isotopes, is challenging due to the low energies (Emax ≤ 300 keV) and short penetration depths (≤ 0.6 mm) in aqueous media. The activity of biologically relevant β-emitters is usually measured in liquid scintillation cocktail (LSC), a mixture of energy-absorbing organic solvents, surfactants, and scintillant fluorophores, which places significant limitations on the ability to acquire time-resolved measurements directly in aqueous biological systems...
January 12, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29327743/the-unexpected-racemization-and-hydrogen-deuterium-exchange-of-the-hydrogen-at-the-%C3%AE-carbon-of-proline-analogs-containing-the-5-azoniaspiro-4-4-nonyl-group
#11
B Setner, M Wierzbicka, L Jerzykiewicz, M Lisowski, Z Szewczuk
Recently, we developed a novel non-fragmenting quaternary ammonium ionization tag for the mass spectrometric sensitive sequencing of peptides, based on the N-spiro proline residue (5-azoniaspiro[4.4.]nonyl-carbonyl). Herein, we present an unexpected racemization and the hydrogen-deuterium exchange (HDX) at the α-C atom of the proline derivative under basic aqueous conditions (1% water solution of triethylamine). The deuterium atom, substituted for the α-C atom, does not undergo back-exchange under acidic aqueous conditions which makes the deuterated isotopologue a promising stabile isotope-coded internal standard for quantitative analysis by mass spectrometry...
January 12, 2018: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29327466/analysis-of-trace-levels-of-impurities-and-hydrogen-isotopes-in-helium-purge-gas-using-gas-chromatography-for-tritium-extraction-system-of-an-indian-lead-lithium-ceramic-breeder-test-blanket-module
#12
V Gayathri Devi, Amit Sircar, Deepak Yadav, Jayraj Parmar
In the fusion fuel cycle, the accurate analysis and understanding of the chemical composition of any gas mixture is of great importance for the efficient design of a tritium extraction and purification system or any tritium handling system. Methods like laser Raman spectroscopy and gas chromatography with thermal conductivity detector have been considered for hydrogen isotopes analyses in fuel cycles. Gas chromatography with a cryogenic separation column has been used for the analysis of hydrogen isotopes gas mixtures in general due to its high reliability and ease of operation...
January 12, 2018: Journal of Separation Science
https://www.readbyqxmd.com/read/29327354/a-validated-liquid-chromatography-high-resolution-tandem-mass-spectrometry-method-for-the-simultaneous-quantitation-of-tryptophan-kynurenine-kynurenic-acid-and-quinolinic-acid-in-human-plasma
#13
Kathrin Arnhard, Florian Pitterl, Barbara Sperner-Unterweger, Dietmar Fuchs, Therese Koal, Herbert Oberacher
Tryptophan (TRP) catabolism via the kynurenine pathway is considered to represent a major link between inflammation and various diseases, including neurodegenerative disorders, depression, schizophrenia, multiple sclerosis, cardiovascular disease, and cancer. The kynurenine pathway and levels of TRP and its metabolites kynurenine (KYN), kynurenic acid (KYNA) and quinolinic acid (QUIN) are well regulated under physiological conditions but may be altered as part of the activated immune response. A simple, sensitive and specific liquid chromatography-time of flight mass spectrometry method was developed for determining levels of the four compounds in human plasma samples...
January 12, 2018: Electrophoresis
https://www.readbyqxmd.com/read/29325415/recrystallization-of-manganite-%C3%AE-mnooh-and-implications-for-trace-element-cycling
#14
Tobias Hens, Joël Brugger, Susan Cumberland, Barbara Etschmann, Andrew J Frierdich
The recrystallization of Mn(III,IV) oxides is catalyzed by aqueous Mn(II) (Mn(II)aq) during (bio)geochemical Mn redox cycling. It is poorly understood how trace metals associated with Mn oxides (e.g., Ni) are cycled during such recrystallization. Here, we use X-ray absorption spectroscopy (XAS) to examine the speciation of Ni associated with manganite (γ-Mn(III)OOH) suspensions in the presence or absence of Mn(II)aq under variable pH conditions (pH 5.5 and 7.5). In a second set of experiments, we used a 62Ni isotope tracer to quantify the amount of dissolved Ni that exchanges with Ni incorporated in the manganite crystal structure during reactions in 1 mM Mn(II)aq and in Mn(II)-free solutions...
January 11, 2018: Environmental Science & Technology
https://www.readbyqxmd.com/read/29325413/direct-detection-of-hardly-detectable-hidden-chirality-of-hydrocarbons-and-deuterated-isotopomers-by-a-helical-polyacetylene-through-chiral-amplification-and-memory
#15
Katsuhiro Maeda, Daisuke Hirose, Natsuki Okoshi, Kouhei Shimomura, Yuya Wada, Tomoyuki Ikai, Shigeyoshi Kanoh, Eiji Yashima
We report the first direct chirality sensing of a series of chiral hydrocarbons and isotopically-chiral compounds (deuterated isotopomers), which are almost impossible to detect by conventional optical spectroscopic methods, by a stereoregular polyacetylene bearing 2,2'-biphenol-derived pendants. The polyacetylene showed a circular dichroism due to a preferred-handed helix formation in response to the hardly detectable hidden chirality of saturated tertiary or chiroptical quaternary hydrocarbons, and deuterated isotopomers...
January 11, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29324791/sediment-biomarkers-elucidate-the-holocene-ontogeny-of-a-shallow-lake
#16
T E Arnold, W F Kenney, J H Curtis, T S Bianchi, M Brenner
We carried out geochemical analyses on a sediment core from Lake Harris, Florida (USA) to identify sources of organic matter to the sediment throughout the Holocene, and relate changes in those sources to shifts in past climate and environmental conditions. We hypothesized that the sources of organic matter changed in response to regional hydrologic shifts following de-glaciation, and to human population expansion in the state during the 20th century. Hydroclimate shifts in Florida were related to: 1) a steady rise in relative sea level and the fresh water table that began in the early Holocene, 2) wetland formation and expansion ca...
2018: PloS One
https://www.readbyqxmd.com/read/29324280/effective-phospholipids-removing-microelution-solid-phase-extraction-lc-ms-ms-method-for-simultaneous-plasma-quantification-of-aripiprazole-and-dehydro-aripiprazole-application-to-human-pharmacokinetic-studies
#17
Aneta Wojnicz, Carmen Belmonte, Dora Koller, Ana Ruiz-Nuño, Manuel Román, Dolores Ochoa, Francisco Abad Santos
A simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for simultaneous quantification of aripiprazole and its active metabolite, dehydro-aripiprazole, in human plasma. Stable isotopically labeled aripiprazole, aripiprazole-D8, has been used as the internal standard (IS) for both analytes. Only 200 μl of human plasma was needed for analyte extraction, using effective phospholipids-eliminating three-step microelution-solid-phase extraction (SPE, Oasis PRiME HLB 96-well μElution Plate)...
December 28, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/29323663/multiplexed-proteome-analysis-with-neutron-encoded-stable-isotope-labeling-in-cells-and-mice
#18
Katherine A Overmyer, Stefka Tyanova, Alex S Hebert, Michael S Westphall, Jürgen Cox, Joshua J Coon
We describe a protocol for multiplexed proteomic analysis using neutron-encoded (NeuCode) stable isotope labeling of amino acids in cells (SILAC) or mice (SILAM). This method currently enables simultaneous comparison of up to nine treatment and control proteomes. Another important advantage over traditional SILAC/SILAM is that shorter labeling times are required. Exploiting the small mass differences that correspond to subtle differences in the neutron-binding energies of different isotopes, the amino acids used in NeuCode SILAC/SILAM differ in mass by just a few milliDaltons...
January 2018: Nature Protocols
https://www.readbyqxmd.com/read/29323490/activity-related-microsecond-dynamics-revealed-by-temperature-jump-f%C3%A3-rster-resonance-energy-transfer-measurements-on-thermophilic-alcohol-dehydrogenase
#19
Morgan B Vaughn, Jianyu Zhang, Thomas G Spiro, R Brian Dyer, Judith P Klinman
Previous studies of a thermophilic alcohol dehydrogenase (ht-ADH) demonstrated a range of discontinuous transitions at 30 °C that include catalysis, kinetic isotope effects, protein hydrogen-deuterium exchange rates, and intrinsic fluorescence properties. Using the Förster resonance energy transfer response from a Trp-NADH donor-acceptor pair in T-jump studies of ht-ADH, we now report microsecond protein motions that can be directly related to active site chemistry. Two distinctive transients are observed: a slow, kinetic process lacking a temperature break, together with a faster transient that is only detectable above 30 °C...
January 11, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29323418/synthesis-of-2-d-acrylamide
#20
Alexey V Salin, Rashid Z Musin
2-d-Acrylamide was synthesized via the two-step procedure starting from acrylonitrile and deuterium oxide. This procedure affords 2-d-acrylamide in 99.9% chemical purity and 98.4% isotopic enrichment.
January 11, 2018: Journal of Labelled Compounds & Radiopharmaceuticals
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