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https://www.readbyqxmd.com/read/29052995/b-c6f5-3-catalyzed-regioselective-deuteration-of-electron-rich-aromatic-and-heteroaromatic-compounds
#1
Wu Li, Ming-Ming Wang, Yuya Hu, Thomas Werner
Deuterium labeled compounds find widespread application in life science. Herein, the deuteration of electron-rich (hetero)aromatic compounds employing B(C6F5)3 as the catalyst and D2O as the deuterium source is reported. This protocol is highly efficient, simply manipulated, and successfully applied in the deuteration of 23 substrates including natural neurotransmitter-like melatonin. It is assumed that the weakening of the O-D bond ultimately results in the formation of electrophilic D(+).
October 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/29052671/quantum-confinement-of-molecular-deuterium-clusters-in-carbon-nanotubes-ab-initio-evidence-for-hexagonal-close-packing
#2
María Pilar de Lara-Castells, Andreas W Hauser, Alexander O Mitrushchenkov, Ricardo Fernández-Perea
An ab initio study of quantum confinement of deuterium clusters in carbon nanotubes is presented. First, density functional theory (DFT)-based symmetry-adapted perturbation theory is used to derive parameters for a pairwise potential model describing the adsorbate-nanotube interaction. Next, we analyze the quantum nuclear motion of N D2 molecules (N < 4) confined in carbon nanotubes using a highly accurate adsorbate-wave-function-based approach, and compare it with the motion of molecular hydrogen. We further apply an embedding approach and study zero-point energy effects on larger hexagonal and heptagonal structures of 7-8 D2 molecules...
October 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29051378/quantum-control-of-molecular-collisions-at-1-kelvin
#3
William E Perreault, Nandini Mukherjee, Richard N Zare
Measurement of vector correlations in molecular scattering is an indispensable tool for mapping out interaction potentials. In a coexpanded supersonic beam, we have studied the rotationally inelastic process wherein deuterium hydride (HD) (v = 1, j = 2) collides with molecular deuterium (D2) to form HD (v = 1, j = 1), where v and j are the vibrational and rotational quantum numbers, respectively. HD (v = 1, j = 2) was prepared by Stark-induced adiabatic Raman passage, with its bond axis aligned preferentially parallel or perpendicular to the lab-fixed relative velocity...
October 20, 2017: Science
https://www.readbyqxmd.com/read/29051376/defibrillation-of-soft-porous-metal-organic-frameworks-with-electric-fields
#4
A Knebel, B Geppert, K Volgmann, D I Kolokolov, A G Stepanov, J Twiefel, P Heitjans, D Volkmer, J Caro
Gas transport through metal-organic framework membranes (MOFs) was switched in situ by applying an external electric field (E-field). The switching of gas permeation upon E-field polarization could be explained by the structural transformation of the zeolitic imidazolate framework ZIF-8 into polymorphs with more rigid lattices. Permeation measurements under a direct-current E-field poling of 500 volts per millimeter showed reversibly controlled switching of the ZIF-8 into polar polymorphs, which was confirmed by x-ray diffraction and ab initio calculations...
October 20, 2017: Science
https://www.readbyqxmd.com/read/29051033/description-of-analytical-method-and-clinical-utility-of-measuring-serum-7-alpha-hydroxy-4-cholesten-3-one-7ac4-by-mass-spectrometry
#5
Leslie J Donato, Alan Lueke, Stacy M Kenyon, Jeffrey W Meeusen, Michael Camilleri
BACKGROUND: Imbalance of bile acids (BA) homeostasis in the gastrointestinal tract can lead to chronic diarrhea or constipation when BA in the colon are in excess or low, respectively. Since both disturbances of bowel function can result from other etiologies, identifying BA imbalance is important to tailor treatment strategies. Serum concentrations of 7-alpha-hydroxy-4-cholesten-3-one (7aC4), a precursor in bile acid synthesis, reflect BA homeostasis. Here we describe a method to accurately measure serum 7aC4 and evaluate the clinical utility in patients with diarrhea or constipation phenotypes...
October 16, 2017: Clinical Biochemistry
https://www.readbyqxmd.com/read/29049865/interrogating-membrane-protein-conformational-dynamics-within-native-lipid-compositions
#6
Eamonn Reading, Zoe Hall, Chloe Martens, Tabasom Haghighi, Heather Findlay, Zainab Ahdash, Argyris Politis, Paula J Booth
Membrane protein-lipid interplay is important for cellular function, however, tools enabling the interrogation of protein dynamics within native lipid environments are scarce and often invasive. We establish that the styrene-maleic acid anhydride lipid particle (SMALP) technology can be coupled with hydrogen-deuterium exchange mass spectrometry (HDX-MS) to investigate membrane protein conformational dynamics within native lipid bilayers. We demonstrate changes in accessibility and dynamics of the rhomboid protease, GlpG, captured within three different native lipid compositions, and identify protein regions sensitive to changes in the native lipid environment...
October 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/29046335/molecular-basis-for-inner-kinetochore-configuration-through-rwd-domain-peptide-interactions
#7
Florian Schmitzberger, Magdalena M Richter, Yuliya Gordiyenko, Carol V Robinson, Michał Dadlez, Stefan Westermann
Kinetochores are dynamic cellular structures that connect chromosomes to microtubules. They form from multi-protein assemblies that are evolutionarily conserved between yeasts and humans. One of these assemblies-COMA-consists of subunits Ame1(CENP-U), Ctf19(CENP-P), Mcm21(CENP-O) and Okp1(CENP-Q) A description of COMA molecular organization has so far been missing. We defined the subunit topology of COMA, bound with inner kinetochore proteins Nkp1 and Nkp2, from the yeast Kluyveromyces lactis, with nanoflow electrospray ionization mass spectrometry, and mapped intermolecular contacts with hydrogen-deuterium exchange coupled to mass spectrometry...
October 18, 2017: EMBO Journal
https://www.readbyqxmd.com/read/29045349/male-specific-association-between-fat-free-mass-index-and-faecal-microbiota-in-2-to-3-year-old-australian-children
#8
Paula Smith-Brown, Mark Morrison, Lutz Krause, Peter S W Davies
OBJECTIVES: Maturation of the gut microbiota has been shown to influence childhood growth while alterations in microbiota composition are proposed to be causally related to the development of overweight and obesity. The objective of this study is to explore the association between microbiota profile, body size and body composition in young children. METHODS: Faecal microbiota was examined by 16S rRNA gene sequencing while body composition was assessed using the deuterium oxide dilution technique in a cohort of 37 well-nourished 2 to 3 year old Australian children...
October 17, 2017: Journal of Pediatric Gastroenterology and Nutrition
https://www.readbyqxmd.com/read/29044719/alkyl-and-aryl-thiol-addition-to-1-1-1-propellane-scope-and-limitations-of-a-fast-conjugation-reaction
#9
Robin M Bär, Stefan Kirschner, Martin Nieger, Stefan Bräse
Herein we report the addition of different thiols to the strained carbon-carbon bond of [1.1.1]propellane (1). We investigated the reaction pathway, performed the addition with substituted thiols, hydrogen sulfide and protected cysteine and verified further modifications of the products. The clean reaction proceeds probably through a radical chain process as we confirmed with different deuterium labelling experiments. It shows great functional group tolerance as halogen-, hydroxy-, methoxy-, carboxy-, amino- and nitro-substituted thiols could be added to 1 with few by-products in 16-90% yield...
October 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29043808/cobalt-catalyzed-oxidative-cyclization-of-benzamides-with-maleimides-synthesis-of-isoindolone-spirosuccinimides
#10
Ramasamy Manoharan, Masilamani Jeganmohan
The oxidative cyclization of substituted benzamides with maleimides assisted by 8-aminoquinoline in the presence of a catalytic amount of Co(OAc)2·4H2O provides isoindolone spirosuccinimides in good to excellent yields. The cyclization reaction was compatible with various substituted benzamides and maleimides. A possible reaction mechanism involving the C-H bond activation as a key step was proposed. The competition experiment and deuterium labeling studies were performed to investigate the mechanism of the reaction...
October 18, 2017: Organic Letters
https://www.readbyqxmd.com/read/29043713/bioorthogonal-chemical-imaging-of-metabolic-changes-during-epithelial-mesenchymal-transition-of-cancer-cells-by-stimulated-raman-scattering-microscopy
#11
Luyuan Zhang, Wei Min
Study of metabolic changes during epithelial-mesenchymal transition (EMT) of cancer cells is important for basic understanding and therapeutic management of cancer progression. We here used metabolic labeling and stimulated Raman scattering (SRS) microscopy, a strategy of bioorthogonal chemical imaging, to directly visualize changes in anabolic metabolism during cancer EMT at a single-cell level. MCF-7 breast cancer cell is employed as a model system. Four types of metabolites (amino acids, glucose, fatty acids, and choline) are labeled with either deuterium or alkyne (C≡C) tag...
October 2017: Journal of Biomedical Optics
https://www.readbyqxmd.com/read/29042625/radiation-resistance-of-silicon-carbide-schottky-diode-detectors-in-d-t-fusion-neutron-detection
#12
Linyue Liu, Ao Liu, Song Bai, Ling Lv, Peng Jin, Xiaoping Ouyang
Silicon carbide (SiC) is a wide band-gap semiconductor material with many excellent properties, showing great potential in fusion neutron detection. The radiation resistance of 4H-SiC Schottky diode detectors was studied experimentally by carefully analyzing the detectors' properties before and after deuterium-tritium fusion neutron irradiation with the total fluence of 1.31 × 10(14) n/cm(2) and 7.29 × 10(14) n/cm(2) at room temperature. Significant degradation has been observed after neutron irradiation: reverse current increased greatly, over three to thirty fold; Schottky junction was broken down; significant lattice damage was observed at low temperature photoluminescence measurements; the peaks of alpha particle response spectra shifted to lower channels and became wider; the charge collection efficiency (CCE) decreased by about 7...
October 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29042591/diffusion-and-distribution-of-deuterium-in-scandium-deuteride-thin-films-under-irradiation-of-deuterium-ion-beam
#13
Tao Wang, Jidong Long, Shiwei Wang, Zhen Yang, Jie Li, Gang Huang, Linwen Zhang, Allen Jian Yang, Xiao Renshaw Wang
Scandium deuteride (ScDx) thin films, as an alternative target for deuterium-deuterium (D-D) reaction, are a very important candidate for detection and diagnostic applications. Albeit with their superior thermal stability, the ignorance of the stability of ScDx under irradiation of deuterium ion beam hinders the realization of their full potential. In this report, we characterize ScDx thin films with scanning electron microscopy (SEM) and X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS) and elastic recoil detection analysis (ERDA)...
October 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29040768/overview-of-neutron-measurements-in-jet-fusion-device
#14
P Batistoni, R Villari, B Obryk, L W Packer, I E Stamatelatos, S Popovichev, A Colangeli, B Colling, N Fonnesu, S Loreti, A Klix, M Klosowski, K Malik, J Naish, M Pillon, T Vasilopoulou, P De Felice, M Pimpinella, L Quintieri
The design and operation of ITER experimental fusion reactor requires the development of neutron measurement techniques and numerical tools to derive the fusion power and the radiation field in the device and in the surrounding areas. Nuclear analyses provide essential input to the conceptual design, optimisation, engineering and safety case in ITER and power plant studies. The required radiation transport calculations are extremely challenging because of the large physical extent of the reactor plant, the complexity of the geometry, and the combination of deep penetration and streaming paths...
October 5, 2017: Radiation Protection Dosimetry
https://www.readbyqxmd.com/read/29038582/direct-visualization-of-critical-hydrogen-atoms-in-a-pyridoxal-5-phosphate-enzyme
#15
Steven Dajnowicz, Ryne C Johnston, Jerry M Parks, Matthew P Blakeley, David A Keen, Kevin L Weiss, Oksana Gerlits, Andrey Kovalevsky, Timothy C Mueser
Enzymes dependent on pyridoxal 5'-phosphate (PLP, the active form of vitamin B6) perform a myriad of diverse chemical transformations. They promote various reactions by modulating the electronic states of PLP through weak interactions in the active site. Neutron crystallography has the unique ability of visualizing the nuclear positions of hydrogen atoms in macromolecules. Here we present a room-temperature neutron structure of a homodimeric PLP-dependent enzyme, aspartate aminotransferase, which was reacted in situ with α-methylaspartate...
October 16, 2017: Nature Communications
https://www.readbyqxmd.com/read/29035497/conformational-dynamics-of-dna-binding-and-cas3-recruitment-by-the-crispr-rna-guide-cascade-complex
#16
Paul B G van Erp, Angela Patterson, Ravi Kant, Luke Berry, Sarah M Golden, Brittney L Forsman, Joshua Carter, Ryan N Jackson, Brian Bothner, Blake Wiedenheft
Bacteria and archaea rely on CRISPR (clustered regularly interspaced short palindromic repeats) RNA-guided adaptive immune systems for sequence specific elimination of foreign nucleic acids. In Escherichia coli, short CRISPR-derived RNAs (crRNAs) assemble with Cas (CRISPR-associated) proteins into a 405-kilodalton multi-subunit surveillance complex called Cascade (CRISPR-associated complex for antiviral defense). Cascade binds foreign DNA complementary to the crRNA guide and recruits Cas3, a trans-acting nuclease-helicase required for target degradation...
October 16, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/29034914/local-water-sensing-water-exchange-in-bacterial-photosynthetic-reaction-centers-embedded-in-a-trehalose-glass-studied-using-multiresonance-epr
#17
Anna Nalepa, Marco Malferrari, Wolfgang Lubitz, Giovanni Venturoli, Klaus Möbius, Anton Savitsky
Using isotope labeled water (D2O and H2(17)O) and pulsed W-band (94 GHz) high-field multiresonance EPR spectroscopies, such as ELDOR-detected NMR and ENDOR, the biologically important question of detection and quantification of local water in proteins is addressed. A bacterial reaction center (bRC) from Rhodobacter sphaeroides R26 embedded into a trehalose glass matrix is used as a model system. The bRC hosts the two native radical cofactor ions (primary electron donor) and (primary electron acceptor) as well as an artificial nitroxide spin label site-specifically attached to the surface of the H-protein domain...
October 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29030693/funaria-hygrometrica-hedw-elevated-tolerance-to-d2o-its-use-for-the-production-of-highly-deuterated-metabolites
#18
Fredd Vergara, Misao Itouga, Roberto Gamboa Becerra, Masami Hirai, José Juan Ordaz-Ortiz, Robert Winkler
The method introduced here to grow F. hygrometrica in high concentrations of D 2 O is an excellent alternative to produce highly deuterated metabolites with broad applications in metabolic studies. Our mass spectrometry experiments strongly indicate the successful incorporation of deuterium into organic compounds. Deuterated metabolites are useful tracers for metabolic studies, yet their wide utilization in research is limited by the multi-step total synthesis required to produce them in the laboratory. Alternatively, deuterated metabolites can be obtained from organisms grown in D2O or deuterated nutrients...
October 13, 2017: Planta
https://www.readbyqxmd.com/read/29030638/uhplc-ms-ms-determination-of-varietal-thiol-precursors-in-sauvignon-blanc-grapes
#19
Andreja Vanzo, Lucija Janeš, Franc Požgan, Špela Velikonja Bolta, Paolo Sivilotti, Klemen Lisjak
Varietal thiol precursors in grapes are subject to metabolic changes during post-harvest treatments. Metabolic activity should therefore be limited after sampling to understand their biosynthesis in the berry and genetic regulation. In this study, berries were frozen in liquid nitrogen immediately after harvesting, transported in dry ice, stored briefly at -80 °C, cryo-milled and extracted without being thawed in cold methanol in a ratio of 1:4 (w/v). A UHPLC-MS/MS method for quantitative determination of the thiol precursors 3-S-glutathionylhexan-1-ol (G3MH), 3-S-cysteinylhexan-1-ol (Cys3MH), 4-S-glutathionyl-4-methylpentan-2-one (G4MMP) and 4-S-cysteinyl-4-methylpentan-2-one (Cys4MMP), glutathione, oxidized glutathione and L-methionine in grapes was developed...
October 13, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29030554/hdx-reveals-the-conformational-dynamics-of-dna-sequence-specific-vdr-co-activator-interactions
#20
Jie Zheng, Mi Ra Chang, Ryan E Stites, Yong Wang, John B Bruning, Bruce D Pascal, Scott J Novick, Ruben D Garcia-Ordonez, Keith R Stayrook, Michael J Chalmers, Jeffrey A Dodge, Patrick R Griffin
The vitamin D receptor/retinoid X receptor-α heterodimer (VDRRXRα) regulates bone mineralization via transcriptional control of osteocalcin (BGLAP) gene and is the receptor for 1α,25-dihydroxyvitamin D3 (1,25D3). However, supra-physiological levels of 1,25D3 activates the calcium-regulating gene TRPV6 leading to hypercalcemia. An approach to attenuate this adverse effect is to develop selective VDR modulators (VDRMs) that differentially activate BGLAP but not TRPV6. Here we present structural insight for the action of a VDRM compared with agonists by employing hydrogen/deuterium exchange...
October 13, 2017: Nature Communications
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