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chemical shift

Jing Xie, Harrison A Neal, Jennifer Szymanowski, Peter C Burns, Todd M Alam, May Nyman, Laura Gagliardi
We obtained a kerosene-soluble form of the lithium salt [UO2 (O2 )(OH)2 ]24 phase (Li-U24 ), by adding cetyltrimethylammonium bromide surfactant to aqueous Li-U24 . Interestingly, its variable-temperature solution 7 Li NMR spectroscopy resolves two narrowly spaced resonances down to -10 °C, which shift upfield with increasing temperature, and finally coalesce at temperatures > 85 °C. Comparison with solid-state NMR demonstrates that the Li dynamics in the Li-U24 -CTA phase involves only exchange between different local encapsulated environments...
April 18, 2018: Inorganic Chemistry
Christian Köhler, Göran Carlström, Stefan Tångefjord, Tineke Papavoine, Matti Lepistö, Karl Edman, Mikael Akke
The glucocorticoid receptor (GR) is a nuclear hormone receptor that regulates key genes controlling development, metabolism, and the immune response. GR agonists are efficacious for treatment of inflammatory, allergic, and immunological disorders. Steroid hormone binding to the ligand-binding domain (LBD) of GR is known to change the structural and dynamical properties of the receptor, which in turn control its interactions with DNA and various co-regulators and drive the pharmacological response. Previous biophysical studies of the GR LBD have required the use of mutant forms to overcome issues with limited protein stability and high aggregation propensity...
April 17, 2018: Biomolecular NMR Assignments
Cyril Charlier, T Reid Alderson, Joseph M Courtney, Jinfa Ying, Philip Anfinrud, Adriaan Bax
In general, small proteins rapidly fold on the timescale of milliseconds or less. For proteins with a substantial volume difference between the folded and unfolded states, their thermodynamic equilibrium can be altered by varying the hydrostatic pressure. Using a pressure-sensitized mutant of ubiquitin, we demonstrate that rapidly switching the pressure within an NMR sample cell enables study of the unfolded protein under native conditions and, vice versa, study of the native protein under denaturing conditions...
April 16, 2018: Proceedings of the National Academy of Sciences of the United States of America
T Katherine Tamai, Yusuke Nakane, Wataru Ota, Akane Kobayashi, Masateru Ishiguro, Naoya Kadofusa, Keisuke Ikegami, Kazuhiro Yagita, Yasufumi Shigeyoshi, Masaki Sudo, Taeko Nishiwaki-Ohkawa, Ayato Sato, Takashi Yoshimura
Chronic circadian disruption due to shift work or frequent travel across time zones leads to jet-lag and an increased risk of diabetes, cardiovascular disease, and cancer. The development of new pharmaceuticals to treat circadian disorders, however, is costly and hugely time-consuming. We therefore performed a high-throughput chemical screen of existing drugs for circadian clock modulators in human U2OS cells, with the aim of repurposing known bioactive compounds. Approximately 5% of the drugs screened altered circadian period, including the period-shortening compound dehydroepiandrosterone (DHEA; also known as prasterone)...
April 17, 2018: EMBO Molecular Medicine
B Dustin Pooler, Diego Hernando, Jeannine A Ruby, Hiroshi Ishii, Ann Shimakawa, Scott B Reeder
BACKGROUND: Current chemical-shift-encoded (CSE) MRI techniques for measuring hepatic proton density fat fraction (PDFF) are sensitive to motion artifacts. PURPOSE: Initial validation of a motion-robust 2D-sequential CSE-MRI technique for quantification of hepatic PDFF. STUDY TYPE: Phantom study and prospective in vivo cohort. POPULATION: Fifty adult patients (27 women, 23 men, mean age 57.2 years). FIELD STRENGTH/SEQUENCE: 3D, 2D-interleaved, and 2D-sequential CSE-MRI acquisitions at 1...
April 17, 2018: Journal of Magnetic Resonance Imaging: JMRI
Tairan Yuwen, Lewis E Kay, Guillaume Bouvignies
Chemical exchange saturation transfer (CEST) has recently evolved into a powerful approach for studying sparsely populated, "invisible" protein states in slow exchange with a major, visible conformer. Central to the technique is the use of a weak, highly selective radio-frequency field that is applied at different frequency offsets in successive experiments, "searching" for minor state resonances. The recording of CEST profiles with enough points to ensure coverage of the entire spectrum at sufficient resolution can be time-consuming, especially for applications that require high static magnetic-fields or when small chemical shift differences between exchanging states must be quantified...
April 17, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Antonio Togni, Carl Philipp Rosenau, Benson J Jelier, Alvar D Gossert
Fluorine chemistry has taken a pivotal role in chemical reaction discovery, drug development, and chemical biology. NMR spectroscopy, arguably the most important technique for characterization of fluorinated compounds, is rife with highly inconsistent referencing of fluorine NMR chemical shifts, producing deviations larger than 1 ppm. Herein, we provide unprecedented evidence that both spectrometer design and the current unified scale system underpinning the calibration of heteronuclear NMR spectra has unintentionally led to widespread variation in the standardization of 19F NMR spectral data...
April 16, 2018: Angewandte Chemie
Yoon-Hui Sung, David Eliezer
The Parkinson's protein alpha-synuclein binds to synaptic vesicles in vivo and adopts a highly extended helical conformation when binding to lipid vesicles in vitro. High-resolution structural analysis of alpha-synuclein bound to small lipid or detergent micelles revealed two helices connected by a non-helical linker, but corresponding studies of the vesicle-bound extended-helix state are hampered by the size and heterogeneity of the protein-vesicle complex. Here we employ fluorinated alcohols (FAs) to induce a highly helical aggregation-resistant state of alpha-synuclein in solution that resembles the vesicle-bound extended-helix state but is amenable to characterization using high-resolution solution-state NMR...
April 16, 2018: Protein Science: a Publication of the Protein Society
Tomaz Cendak, Lisa Sequeira, Mariana Sardo, Anabela Valente, Moisés Pinto, Luís Mafra
The wealth of site-selective structural information on CO2 speciation, obtained by spectroscopic techniques, is often hampered by the lack of easy-to-control synthetic routes. Herein, an alternative experimental protocol that relies on the high sensitivity of 13C chemical shift anisotropy (CSA) tensors to proton-transfer, is presented to unambiguously distinguish between ionic/charged and neutral CO2 species, formed upon adsorption of 13CO2 in amine-modified porous materials. Control of the surface amine spacing was achieved through the use of amine protecting groups during functionalization prior to CO2 adsorption...
April 16, 2018: Chemistry: a European Journal
Sujoy Ghosh, Niazul I Khan, John G Tsavalas, Edward Song
Selective and rapid detection of biomarkers is of utmost importance in modern day health care for early stage diagnosis to prevent fatal diseases and infections. Among several protein biomarkers, the role of lysozyme has been found to be especially important in human immune system to prevent several bacterial infections and other chronic disease such as bronchopulmonary dysplasia. Thus, real-time monitoring of lysozyme concentration in a human body can pave a facile route for early warning for potential bacterial infections...
2018: Frontiers in Bioengineering and Biotechnology
Tom Aharoni, Amir Goldbourt
The capsid dynamics of filamentous bacteriophages is related to their function, stability and interactions with the genome, and can be assessed by measuring the chemical shift anisotropy (CSA) of 15N-amides, which are sensitive to large amplitude motions. In this study, we used CSA recoupling experiments under magic-angle spinning NMR in order to probe the dynamics of the y21m capsid mutant of fd bacteriophage. We show, based on fitting those generated CSA lineshapes, that residues located in the N-terminus undergo increased motional amplitudes suggesting its global motion, while other backbone residues are rigid, and imply on a tight hydrophobic packing of the phage...
April 16, 2018: Chemistry: a European Journal
Shila Shirdel Ghadikolaei, Abdollah Omrani, Morteza Ehsani
The BCNs were chemically modified using acetic anhydride with the aim of improving its dispersion and interfacial adhesion. Acetylation of BCNs was confirmed by FT-IR spectroscopy. Morphology studies using TEM and SEM revealed that a reasonable dispersion of the modified BCNs in the EVA matrix was accomplished. The DSC data displayed a little shift in the Tg to higher temperatures with the incorporation of both modified and unmodified BCNs. Increased thermal stability of the nanocomposites consisting acetylated BCNs was confirmed by TGA technique...
April 13, 2018: International Journal of Biological Macromolecules
Ina Oestroem, Alexandre Osmar Ortolan, Felipe Silveira de Souza Schneider, Giovanni Finoto Caramori, Renato Luis Tame Parreira
Molecular iron maidens are a strained type of cyclophane in which a methine hydrogen, by the action of the bridges, is placed closer to the center of an aromatic ring. Such constrained molecular frameworks are in fact a noteworthy synthetic chal- lenge. The present study provides a comprehensible theoretical analysis that elucidates unique structural and energetic aspects of this class of molecules, evaluating, in the light of quantum chemistry, both the influence of the aromatic moiety, from π-basic to π-acid, and the nature of the heteroatoms located at the bridges...
April 16, 2018: Journal of Organic Chemistry
Connie L Engel, M Sharima Rasanayagam, Janet M Gray, Jeanne Rizzo
The authors undertook a scoping review to assess the literature from 2002 to 2017 on the relationship between occupation and female breast cancer. Case-control, cohort, and meta-analytic studies suggest that women working as flight attendants, in medical professions, some production positions, sales and retail, and scientific technical staff are likely to have elevated risk of breast cancer. In addition, occupational exposures to night-shift work, ionizing radiation, some chemicals, job stress, and sedentary work may increase risk of breast cancer...
May 2018: New Solutions: a Journal of Environmental and Occupational Health Policy: NS
Antonis Matakos, James M Balter, Yue Cao
We developed an optimized and robust method to estimate liver B0 field inhomogeneity for monitoring and correcting susceptibility-induced geometric distortion in magnetic resonance images for precision therapy. A triple-gradient-echo acquisition was optimized for the whole liver B0 field estimation within a single-exhale breath-hold scan on a 3 T scanner. To eliminate chemical-shift artifacts, fat signals were chosen in-phase between 2 echoes with an echo time difference (ΔTE) of 2.3 milliseconds. To avoid phase-wrapping, other 2 echoes provided a large field dynamic range (1/ΔTE) to cover the B0 field inhomogeneity...
June 2017: Tomography: a Journal for Imaging Research
Hans W Paerl, Timothy G Otten, Raphael Kudela
Anthropogenic nutrient over-enrichment, coupled with rising temperatures and an increasing frequency of extreme hydrologic events (storms and droughts) are accelerating eutrophication and promoting the expansion of harmful algal blooms (HABs) across the freshwater-to-marine continuum. All HABs-with a focus here on cyanobacterial blooms-pose serious consequences for water supplies, fisheries, recreational uses, tourism and property values. As nutrient loads grow in watersheds, they begin to compound the effects of legacy stores...
April 16, 2018: Environmental Science & Technology
Marion Pupier, Jean-Marc Nuzillard, Julien Wist, Nils E Schlörer, Stefan Kuhn, Mate Erdelyi, Christoph Steinbeck, Antony J Williams, Craig Butts, Tim D W Claridge, Bozhana Mikhova, Wolfgang Robien, Hesam Dashti, Hamid R Eghbalnia, Christophe Farès, Christian Adam, Kessler Pavel, Fabrice Moriaud, Mikhail Elyashberg, Dimitris Argyropoulos, Manuel Pérez, Patrick Giraudeau, Roberto R Gil, Paul Trevorrow, Damien Jeannerat
Even though NMR has found countless applications in the field of small molecule characterization, there is no standard file format available for the NMR data relevant to structure characterization of small molecules. A new format is therefore introduced to associate the NMR parameters extracted from 1D and 2D spectra of organic compounds to the proposed chemical structure. These NMR parameters, which we shall call NMReDATA (for nuclear magnetic resonance extracted data), include chemical shift values, signal integrals, intensities, multiplicities, scalar coupling constants, lists of 2D correlations, relaxation times and diffusion rates...
April 14, 2018: Magnetic Resonance in Chemistry: MRC
John D Persons, Shahid N Khan, Rieko Ishima
This manuscript presents an NMR strategy to investigate conformational differences in protein-inhibitor complexes, when the inhibitors tightly bind to a protein at sub-nanomolar dissociation constants and are highly analogous to each other. Using HIV-1 protease (PR), we previously evaluated amide chemical shift differences, ΔCSPs, of PR bound to darunavir (DRV) compared to PR bound to several DRV analogue inhibitors, to investigate subtle but significant long-distance conformation changes caused by the inhibitor's chemical moiety variation [Khan, S...
April 12, 2018: Methods: a Companion to Methods in Enzymology
Peter O Coe, Steve R Williams, David M Morris, Ed Parkin, Michelle Harvie, Andrew G Renehan, Derek A O'Reilly
BACKGROUND: Excess body adiposity is associated with increased risk of pancreatic cancer, and in animal models excess intra-pancreatic fat is a driver of pancreatic carcinogenesis. Within a programme to evaluate pancreatic fat and PC risk in humans, we assessed whether MR-quantified pancreatic fat fraction (PFF) was 'fit for purpose' as an imaging biomarker. METHODS: We determined PFF using MR spectroscopy (MRS) and MR chemical shift imaging (CS-MR), in two groups...
April 3, 2018: Pancreatology: Official Journal of the International Association of Pancreatology (IAP) ... [et Al.]
Dymytrii Listunov, Carine Duhayon, Albert Poater, Serge Mazères, Alix Saquet, Valérie Maraval, Remi Chauvin
Hexa-tert-butyl-carbo-benzene C18tBu6 and three phenylated counterparts C18tBumPh6-m (m = 4, 2) have been synthesized. The peralkylated version (m = 6) provides experimental access to intrinsic features of the insulated C18 core independently from the influence of π-conjugated substituent. Over the series, structural, spectroscopical and electrochemical properties are compared with those of the hexaphenylated reference (m = 0). Anchoring tBu substituents at the C18 macrocycle is shown to enhance stability and solubility, and to dramatically modify UV-vis absorption and redox properties...
April 13, 2018: Chemistry: a European Journal
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