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https://www.readbyqxmd.com/read/28432929/performance-testing-of-the-neutron-flux-monitors-from-10kev-to-1mev-developed-for-bnct-a-preliminary-study
#1
Xingcai Guan, Masanobu Manabe, Shingo Tamaki, Fuminobu Sato, Isao Murata, Tieshan Wang
The neutron flux monitors from 10keV to 1MeV designed for boron neutron capture therapy (BNCT) were experimentally tested with prototype monitors in an appropriate neutron field produced at the intense deuterium-tritium neutron source facility OKTAVIAN of Osaka University, Japan. The experimental test results and related analysis indicated that the performance of the monitors was good and the neutron fluxes from 10keV to 1MeV of practical BNCT neutron sources can be measured within 10% by the monitors.
April 12, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28431337/a-possible-approach-to-14mev-neutron-moderation-a-preliminary-study-case
#2
D Flammini, R Pilotti, A Pietropaolo
Deuterium-Tritium (D-T) interactions produce almost monochromatic neutrons with about 14MeV energy. These neutrons are used in benchmark experiments as well as for neutron cross sections assessment in fusion reactors technology. The possibility to moderate 14MeV neutrons for purposes beyond fusion is worth to be studied in relation to projects of intense D-T sources. In this preliminary study, carried out using the MCNP Monte Carlo code, the moderation of 14MeV neutrons is approached foreseeing the use of combination of metallic materials as pre-moderator and reflectors coupled to standard water moderators...
April 12, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28431336/beam-induced-back-streaming-electron-suppression-analysis-for-an-accelerator-type-neutron-generator-designed-for-40-ar-39-ar-geochronology
#3
Cory Waltz, Mauricio Ayllon, Tim Becker, Lee Bernstein, Ka-Ngo Leung, Leo Kirsch, Paul Renne, Karl Van Bibber
A facility based on a next-generation, high-flux D-D neutron generator has been commissioned and it is now operational at the University of California, Berkeley. The current generator designed for (40)Ar/(39)Ar dating of geological materials produces nearly monoenergetic 2.45MeV neutrons at outputs of 10(8)n/s. The narrow energy range is advantageous relative to the (235)U fission spectrum neutrons due to (i) reduced (39)Ar recoil energy, (ii) minimized production of interfering argon isotopes from K, Ca, and Cl, and (iii) reduced total activity for radiological safety and waste generation...
April 13, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28431242/structural-and-functional-analysis-of-a-%C3%AE-2-adrenergic-receptor-complex-with-grk5
#4
Konstantin E Komolov, Yang Du, Nguyen Minh Duc, Robin M Betz, João P G L M Rodrigues, Ryan D Leib, Dhabaleswar Patra, Georgios Skiniotis, Christopher M Adams, Ron O Dror, Ka Young Chung, Brian K Kobilka, Jeffrey L Benovic
The phosphorylation of agonist-occupied G-protein-coupled receptors (GPCRs) by GPCR kinases (GRKs) functions to turn off G-protein signaling and turn on arrestin-mediated signaling. While a structural understanding of GPCR/G-protein and GPCR/arrestin complexes has emerged in recent years, the molecular architecture of a GPCR/GRK complex remains poorly defined. We used a comprehensive integrated approach of cross-linking, hydrogen-deuterium exchange mass spectrometry (MS), electron microscopy, mutagenesis, molecular dynamics simulations, and computational docking to analyze GRK5 interaction with the β2-adrenergic receptor (β2AR)...
April 20, 2017: Cell
https://www.readbyqxmd.com/read/28430483/infrared-peak-splitting-from-phonon-localization-in-solid-hydrogen
#5
Ioan B Magdău, Graeme J Ackland
We show that the isotope effect leads to a completely different spectroscopic signal in hydrogen-deuterium mixtures, compared to pure elements that have the same crystal structure. This is particularly true for molecular vibrations, which are the main source of information about the structure of high-pressure hydrogen. Mass disorder breaks translational symmetry, meaning that vibrations are localized almost to single molecules, and are not zone-center phonons. In mixtures, each observable infrared (IR) peak corresponds to a collection of many such molecular vibrations, which have a distribution of frequencies depending on local environment...
April 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28430446/piecing-together-the-allosteric-patterns-of-chaperonin-groel
#6
Jin Chen, Qian Zhang, Weitong Ren, Wenfei Li
Despite considerable effort, elucidating allostery of large macromolecular assemblies at a molecular level in solution remains technically challenging due to its structural complexity. Here we have employed an approach combining amide backbone hydrogen/deuterium exchange coupled with mass spectrometry, fluorescence spectroscopy and molecular simulations to characterize allosteric patterns of chaperonin GroEL, a ~800 kDa tetradecamer from E. coli. Using available crystal structures of GroEL, we quantitatively map out GroEL allosteric changes in solution by resolving exchange behaviors of 133 overlapping proteolytic peptides with more than 95% sequence coverage...
April 21, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28428550/structure-based-dynamic-arrays-in-regulatory-domains-of-sodium-calcium-exchanger-ncx-isoforms
#7
Moshe Giladi, Su Youn Lee, Yarden Ariely, Yotam Teldan, Rotem Granit, Roi Strulovich, Yoni Haitin, Ka Young Chung, Daniel Khananshvili
Mammalian Na(+)/Ca(2+) exchangers, NCX1 and NCX3, generate splice variants, whereas NCX2 does not. The CBD1 and CBD2 domains form a regulatory tandem (CBD12), where Ca(2+) binding to CBD1 activates and Ca(2+) binding to CBD2 (bearing the splicing segment) alleviates the Na(+)-induced inactivation. Here, the NCX2-CBD12, NCX3-CBD12-B, and NCX3-CBD12-AC proteins were analyzed by small-angle X-ray scattering (SAXS) and hydrogen-deuterium exchange mass-spectrometry (HDX-MS) to resolve regulatory variances in the NCX2 and NCX3 variants...
April 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28428354/multiplex-tandem-mass-spectrometry-enzymatic-activity-assay-for-newborn-screening-of-the-mucopolysaccharidoses-and-type-2-neuronal-ceroid-lipofuscinosis
#8
Yang Liu, Fan Yi, Arun Babu Kumar, Naveen Kumar Chennamaneni, Xinying Hong, C Ronald Scott, Michael H Gelb, Frantisek Turecek
BACKGROUND: We expanded the use of tandem mass spectrometry combined with liquid chromatography (LC-MS/MS) for multiplex newborn screening of seven lysosomal enzymes in dried blood spots (DBS). The new assays are for enzymes responsible for the mucopolysaccharidoses (MPS-I, -II, -IIIB, -IVA, -VI, and -VII) and type 2 neuronal ceroid lipofuscinosis (LINCL). METHODS: New substrates were prepared and char-acterized for tripeptidyl peptidase 1 (TPP1), α-N-acetylglucosaminidase (NAGLU), and lysosomal β-glucuronidase (GUSB)...
April 20, 2017: Clinical Chemistry
https://www.readbyqxmd.com/read/28426082/deciphering-of-interactions-between-platinated-dna-and-hmgb1-by-hydrogen-deuterium-exchange-mass-spectrometry
#9
Yuanyuan Wang, Zhifeng Du, Wei Zheng, Kui Wu, Decheng Xu, Qun Luo, Yao Zhao, Juanjuan Han, Yangzhong Liu, Fuyi Wang
A high mobility group box 1 (HMGB1) protein has been reported to recognize both 1,2-intrastrand crosslinked DNA by cisplatin (1,2-cis-Pt-DNA) and monofunctional platinated DNA using trans-[PtCl2(NH3)(thiazole)] (1-trans-PtTz-DNA). However, the molecular basis of recognition between the trans-PtTz-DNA and HMGB1 remains unclear. In the present work, we described a hydrogen/deuterium exchange mass spectrometry (HDX-MS) method in combination with docking simulation to decipher the interactions of platinated DNA with domain A of HMGB1...
April 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28425714/prehydrated-one-electron-attachment-to-azido-modified-pentafuranoses-aminyl-radical-formation-rapid-h-atom-transfer-and-subsequent-ring-opening
#10
Mukesh Mudgal, Sunny Rishi, Daniel A Lumpuy, Keaton A Curran, Kathryn Lynn Verley, Adam J Sobczak, Thao P Dang, Natasha Sulimoff, Anil Kumar, Michael D Sevilla, Stanislaw F Wnuk, Amitava Adhikary
Methyl 2-azido-2-deoxy-α-D-lyxofuranoside (1a) and methyl 2-azido-2-deoxy-β-D-ribofuranoside (2) were prepared from D-xylose or D-arabinose, respectively. Employing ESR and DFT/B3LYP/6-31G* calculations, we investigated (i) aminyl radical (RNH•) formation and (ii) reaction pathways of RNH•. Prehydrated electron attachment to 1a and 2 at 77 K produced transient azide anion radical (RN3•¯) which reacts via rapid N2 loss at 77 K, forming nitrene anion radical (RN•¯). Rapid protonation of RN•¯ at 77 K formed RNH• and ¯OH...
April 20, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28425699/synthesis-of-npn-coordinated-tantalum-alkyl-complexes-and-their-hydrogenolysis-isolation-of-a-terminal-tantalum-hydride-incorporating-a-doubly-cyclometalated-npn-scaffold
#11
Sonja Batke, Malte Sietzen, Hubert Wadepohl, Joachim Ballmann
The closely related benzylene-linked diaminophosphines PhP(CH2C6H4-o-NHPh)2 (AH2) and PhP(C6H4-o-CH2NHXyl)2 (BH2 with Xyl = 3,5-Me2C6H3) were employed for the synthesis of tantalum(V) alkyls, which were then studied with respect to hydrogenolysis. In the case of AH2, the tantalum trimethyl complex [Ta(A)Me3] (1) and the tantalum hydrocarbyl complex [Ta(A)(CH2SiMe3)(η(2)-EtC≡CEt)] (2) were prepared from the ligand's dilithium salt (A)Li2(diox). Upon hydrogenolysis of 1 and 2, the formation of methane and SiMe4, respectively, was observed, but well-defined tantalum hydrides could not be detected...
April 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28424515/structure-and-allosteric-inhibition-of-excitatory-amino-acid-transporter-1
#12
Juan C Canul-Tec, Reda Assal, Erica Cirri, Pierre Legrand, Sébastien Brier, Julia Chamot-Rooke, Nicolas Reyes
Human members of the solute carrier 1 (SLC1) family of transporters take up excitatory neurotransmitters in the brain and amino acids in peripheral organs. Dysregulation of the function of SLC1 transporters is associated with neurodegenerative disorders and cancer. Here we present crystal structures of a thermostabilized human SLC1 transporter, the excitatory amino acid transporter 1 (EAAT1), with and without allosteric and competitive inhibitors bound. The structures reveal architectural features of the human transporters, such as intra- and extracellular domains that have potential roles in transport function, regulation by lipids and post-translational modifications...
April 19, 2017: Nature
https://www.readbyqxmd.com/read/28421218/catalytic-c-h-amination-driven-by-intramolecular-ligand-to-nitrene-one-electron-transfer-through-a-rhodium-iii-centre
#13
Daiki Fujita, Hideki Sugimoto, Yoshihito Shiota, Yuma Morimoto, Kazunari Yoshizawa, Shinobu Itoh
Werner type six-coordinate rhodium(iii) complexes coordinated by a planar trianionic ligand and two axial aniline ligands are synthesised. The trianionic ligand behaves as a redox-active ligand to form a ligand radical species upon one-electron oxidation of the complex. The rhodium(iii) complexes catalyse C-H amination of external substrates such as xanthene with tosylazide as the nitrene source. DFT-calculation and kinetic deuterium isotope effects indicate that a di-radical rhodium(iii) complex formed by one-electron transfer from the redox-active ligand to the nitrene group works as a reactive intermediate to induce aliphatic C-H activation...
April 19, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28418026/the-cac2-subunit-is-essential-for-productive-histone-binding-and-nucleosome-assembly-in-caf-1
#14
Francesca Mattiroli, Yajie Gu, Jeremy L Balsbaugh, Natalie G Ahn, Karolin Luger
Nucleosome assembly following DNA replication controls epigenome maintenance and genome integrity. Chromatin assembly factor 1 (CAF-1) is the histone chaperone responsible for histone (H3-H4)2 deposition following DNA synthesis. Structural and functional details for this chaperone complex and its interaction with histones are slowly emerging. Using hydrogen-deuterium exchange coupled to mass spectrometry, combined with in vitro and in vivo mutagenesis studies, we identified the regions involved in the direct interaction between the yeast CAF-1 subunits, and mapped the CAF-1 domains responsible for H3-H4 binding...
April 18, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28415839/enantioselective-synthesis-of-anti-syn-trihalides-and-anti-syn-anti-tetrahalides-via-asymmetric-%C3%AE-elimination
#15
Yu Tan, Shilong Luo, Dongmei Li, Nan Zhang, Shiqi Jia, Yidong Liu, Wenling Qin, Choong Eui Song, Hailong Yan
Contiguous stereogenic halides are common in natural products as well as bioactive molecules. Unlike the well-known asymmetric vicinal dihalogenation of alkenes for accessing dihalogenated products, a new generation method of contiguous stereogenic halides α,β,γ,δ relative to carbonyl group in excellent enantioselectivity by utilizing a Song's oligoEG catalyst-catalyzed asymmetric β-elimination is proposed in this report. According to this methodology, a wide range of anti-syn-trihalides and anti-syn-anti-tetrahalides with high levels of enantioselectivity were synthesized...
April 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28412025/the-influence-of-chronic-il-6-exposure-in-vivo-on-rat-achilles-tendon-extracellular-matrix
#16
Mark S Katsma, Shivam H Patel, Erica Eldon, Kathryn A Corbell, Kevin L Shimkus, James D Fluckey, Chad C Carroll
When compared to placebo, acetaminophen (APAP) reduces tendon stiffness and collagen cross-linking. APAP also enhances the exercise-induced increase in peritendinous levels of IL-6. Elevated levels of IL-6 are associated with tendinopathy, thus we hypothesized that chronic, elevated peritendinous IL-6 would alter tendon extracellular matrix (ECM). IL-6 (∼3000pgml(-1)) was injected (3dwk(-1) for 8-wks) into the Achilles peritendinous region of male Wistar rats (n=16) with the opposite leg serving as a sham...
April 13, 2017: Cytokine
https://www.readbyqxmd.com/read/28406535/burgess-iridium-i-catalyst-for-selective-hydrogen-isotope-exchange
#17
Annina Burhop, Raphail Prohaska, Remo Weck, Jens Atzrodt, Volker Derdau
We have evaluated the commercially available Burgess catalyst in Hydrogen Isotope Exchange (HIE) reactions with several substrates bearing different directing group functionalities and have obtained moderate to high (50-97%D) deuterium incorporations. The broad applicability in HIE reactions makes the Burgess catalyst a possible alternative compared to other commercially available iridium(I)catalysts.
April 12, 2017: Journal of Labelled Compounds & Radiopharmaceuticals
https://www.readbyqxmd.com/read/28404847/characterization-of-pre-f-gcn4t-a-modified-human-respiratory-syncytial-virus-fusion-protein-stabilized-in-a-non-cleaved-pre-fusion-conformation
#18
Normand Blais, Martin Gagné, Yoshitomo Hamuro, Patrick Rheault, Martine Boyer, Ann-Muriel Steff, Guy Baudoux, Vincent Dewar, Josée Demers, Jean-Louis Ruelle, Denis Martin
Human respiratory syncytial virus (hRSV) fusion protein (F) is considered a major target of the neutralizing antibody response to hRSV. This glycoprotein undergoes a major structural shift from pre- (pre-F) to post-fusion (post-F) state at the time of virus-host cell membrane fusion. Recent evidences suggest that the pre-F state may be a superior target for neutralizing antibodies than post-F. Therefore, for vaccine purposes, we have designed and characterized a recombinant hRSV F protein, called Pre-F-GCN4t, stabilized in a pre-F conformation...
April 12, 2017: Journal of Virology
https://www.readbyqxmd.com/read/28402104/hydrogen-deuterium-exchange-mass-spectrometry-of-human-green-opsin-reveals-a-conserved-pro-pro-motif-in-extracellular-loop-2-of-monostable-visual-g-protein-coupled-receptors
#19
Lukas Hofmann, Nathan S Alexander, Wenyu Sun, Jianye Zhang, Tivadar Orban, Krzysztof Palczewski
Opsins comprise the protein component of light sensitive G protein-coupled receptors (GPCRs) in the retina of the eye that are responsible for the transduction of light into a biochemical signal. Here, we used hydrogen/deuterium (H/D) exchange coupled with mass spectrometry to map conformational changes in green cone opsin upon light activation. We then compared these findings with those reported for rhodopsin. The extent of H/D exchange in green cone opsin was greater than in rhodopsin in the dark and bleached states, suggesting a higher structural heterogeneity for green cone opsin...
April 21, 2017: Biochemistry
https://www.readbyqxmd.com/read/28399628/an-examination-of-mixtures-containing-sphingomyelin-and-cholesterol-by-molecular-dynamics-simulations
#20
Eric Wang, Jeffery B Klauda
The all-atom CHARMM36 (C36) force field is used to simulate bilayers of pure palmitoylsphingomyelin (PSM) as well as binary mixtures of PSM and stearoylsphingomyelin (SSM) at various cholesterol concentrations (XC) and temperatures. C36 simulation data is in good agreement with experimental deuterium order parameters and previous computational results, providing evidence of the utility of the force field for potentially studying more complex membranes. The area compressibility modulus is shown to achieve a large value of 2...
April 11, 2017: Journal of Physical Chemistry. B
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