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https://www.readbyqxmd.com/read/28222392/endor-with-band-selective-shaped-inversion-pulses
#1
Claudia E Tait, Stefan Stoll
Electron Nuclear DOuble Resonance (ENDOR) is based on the measurement of nuclear transition frequencies through detection of changes in the polarization of electron transitions. In Davies ENDOR, the initial polarization is generated by a selective microwave inversion pulse. The rectangular inversion pulses typically used are characterized by a relatively low selectivity, with full inversion achieved only for a limited number of spin packets with small resonance offsets. With the introduction of pulse shaping to EPR, the rectangular inversion pulses can be replaced with shaped pulses with increased selectivity...
February 12, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28222324/graph-based-segmentation-of-abnormal-nuclei-in-cervical-cytology
#2
Ling Zhang, Hui Kong, Shaoxiong Liu, Tianfu Wang, Siping Chen, Milan Sonka
A general method is reported for improving the segmentation of abnormal cell nuclei in cervical cytology images. In automation-assisted reading of cervical cytology, one of the essential steps is the segmentation of nuclei. Despite some progress, there is a need to improve the sensitivity, particularly the segmentation of abnormal nuclei. Our method starts with pre-segmenting the nucleus to define the coarse center and size of nucleus, which is used to construct a graph by image unfolding that maps ellipse-like border in the Cartesian coordinate system to lines in the polar coordinate system...
January 31, 2017: Computerized Medical Imaging and Graphics: the Official Journal of the Computerized Medical Imaging Society
https://www.readbyqxmd.com/read/28222298/vascular-morphogenesis-an-integrin-and-fibronectin-highway
#3
Hellyeh Hamidi, Johanna Ivaska
A new study shows that endothelial cells use synaptic-like machinery to control polarized secretion and deposition of newly synthesised fibronectin. This process is coupled to active integrin recycling to the same locations and is fundamental for vascular development in zebrafish.
February 20, 2017: Current Biology: CB
https://www.readbyqxmd.com/read/28222261/enhanced-release-of-molecules-upon-uv-light-irradiation-from-photoresponsive-hydrogels-prepared-from-bifunctional-azobenzene-and-four-arm-poly-ethylene-glycol
#4
Shiva Kumar Rastogi, Hailee E Anderson, Joseph Lamas, Scott L Barrett, Travis Cantu, Stefan Zauscher, William J Brittain, Tania Betancourt
Advances in biosensors and drug delivery depend on hydrogels that respond to external stimuli. In this work we de-scribe the preparation and characterization of photoresponsive hydrogels prepared by crosslinking of di-NHS ester of azobenzoic acid and four-armed, amine-terminated poly(ethylene glycol). The porous structure and composition of the hydrogels were confirmed by scanning electron microscopy and Fourier transform infrared (FTIR) spectroscopy. The reversible photoisomerization of the azobenzene-containing hydrogel crosslinkers in the gels was confirmed by ab-sorption spectroscopy...
February 21, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28222136/cardiac-strength-interval-curves-calculated-using-a-bidomain-tissue-with-a-parsimonious-ionic-current
#5
Suran K Galappaththige, Richard A Gray, Bradley J Roth
The strength-interval curve plays a major role in understanding how cardiac tissue responds to an electrical stimulus. This complex behavior has been studied previously using the bidomain formulation incorporating the Beeler-Reuter and Luo-Rudy dynamic ionic current models. The complexity of these models renders the interpretation and extrapolation of simulation results problematic. Here we utilize a recently developed parsimonious ionic current model with only two currents-a sodium current that activates rapidly upon depolarization INa and a time-independent inwardly rectifying repolarization current IK-which reproduces many experimentally measured action potential waveforms...
2017: PloS One
https://www.readbyqxmd.com/read/28222105/stat3-cdc25a-dependent-cell-proliferation-promotes-embryonic-axis-extension-during-zebrafish-gastrulation
#6
Yinzi Liu, Diane S Sepich, Lilianna Solnica-Krezel
Cell proliferation has generally been considered dispensable for anteroposterior extension of embryonic axis during vertebrate gastrulation. Signal transducer and activator of transcription 3 (Stat3), a conserved controller of cell proliferation, survival and regeneration, is associated with human scoliosis, cancer and Hyper IgE Syndrome. Zebrafish Stat3 was proposed to govern convergence and extension gastrulation movements in part by promoting Wnt/Planar Cell Polarity (PCP) signaling, a conserved regulator of mediolaterally polarized cell behaviors...
February 2017: PLoS Genetics
https://www.readbyqxmd.com/read/28221812/intermicellar-interactions-and-the-viscoelasticity-of-surfactant-solutions-complementary-use-of-sans-and-saxs
#7
Viviane Lutz-Bueno, Marianne Liebi, Joachim Kohlbrecher, Peter Fischer
In ionic surfactant micelles, basic interactions among distinct parts of surfactant monomers, their counterion, and additives are fundamental to tune molecular self-assembly and enhance viscoelasticity. Here, we investigate the addition of sodium salicylate (NaSal) to hexa-decyltrimethyl ammonium chloride and bromide (CTAC and CTAB) and 1-hexa-decyl pyridinium chloride and bromide (CPyCl and CPyBr), which have distinct counterions and headgroup structures, but the same hydrophobic tail. Different contrasts are obtained from small-angle neutron scattering SANS, which probes differences between the nucleus of atoms, and X-rays SAXS, which probes differences in electron density...
February 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28221804/semiconductor-seeded-nanorods-with-graded-composition-exhibiting-high-quantum-yield-high-polarization-and-minimal-blinking
#8
Ido Hadar, John Patrick Philbin, Yossef Efraim Panfil, Shany Neyshtadt, Itai Lieberman, Hagai Eshet, Sorin Lazar, Eran Rabani, Uri Banin
Seeded semiconductor nanorods represent a unique family of quantum confined materials that manifest characteristics of mixed dimensionality. They show polarized emission with high quantum yield and fluorescence switching under an electric field, features that are desirable for use in display technologies and other optical applications. So far, their robust synthesis has been limited mainly to CdSe/CdS heterostructures, thereby constraining the spectral tunability to the red region of the visible spectrum. Herein we present a novel synthesis of CdSe/Cd1-xZnxS seeded nanorods with radially graded composition that show bright and highly polarized green emission with minimal intermittency, as confirmed by ensemble and single nanorods optical measurements...
February 21, 2017: Nano Letters
https://www.readbyqxmd.com/read/28221785/homogeneous-synthesis-and-electroluminescence-device-of-highly-luminescent-cspbbr3-perovskite-nanocrystals
#9
Song Wei, Yanchun Yang, Xiaojiao Kang, Lan Wang, Lijian Huang, Daocheng Pan
Highly luminescent CsPbBr3 perovskite nanocrystals (PNCs) are homogeneously synthesized by mixing toluene solutions of PbBr2 and cesium oleate at room temperature in open air. We found that PbBr2 can be easily dissolved in nonpolar toluene in the presence of tetraoctylammonium bromide, which allows us to homogeneously prepare CsPbBr3 perovskite quantum dots and prevents the use of harmful polar organic solvents, such as N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone. Additionally, this method can be extended to synthesize highly luminescent CH3NH3PbBr3 perovskite quantum dots...
February 21, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28221775/electrostatic-interactions-as-mediators-in-the-allosteric-activation-of-pka-ri%C3%AE
#10
Emilia Pecora de Barros, Robert D Malmstrom, Kimya Nourbakhsh, Jason Cruz Del Rio, Alexandr P Kornev, Susan S Taylor, Rommie E Amaro
Close-range electrostatic interactions that form salt bridges are key components of protein stability. Here we investigate the role of these charged interactions in modulating the allosteric activation of Protein Kinase A (PKA) via computational and experimental mutational studies on a conserved basic patch located in the regulatory subunit's B/C helix. Molecular dynamics simulations evidenced the presence of an extended network of fluctuating salt bridges spanning the helix and connecting the two cAMP binding domains in its extremities...
February 21, 2017: Biochemistry
https://www.readbyqxmd.com/read/28221726/how-the-molecular-packing-affects-the-room-temperature-phosphorescence-in-pure-organic-compounds-ingenious-molecular-design-detailed-crystal-analysis-and-rational-theoretical-calculations
#11
Yujun Xie, Yuwei Ge, Qian Peng, Conggang Li, Qianqian Li, Zhen Li
Long-lived phosphorescence at room temperature (RTP) from pure organic molecules is rare. Recent research reveals various crystalline organic molecules can realize RTP with lifetimes extending to the magnitude of second. There is little research on how molecular packing affecting RTP. Three compounds are designed with similar optical properties in solution, but tremendously different solid emission characteristics. By investigating the molecular packing arrangement in single crystals, it is found that the packing style of the compact face to face favors of long phosphorescence lifetime and high photoluminescence efficiency, with the lifetime up to 748 ms observed in the crystal of CPM ((9H-carbazol-9-yl)(phenyl)methanone)...
February 21, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28221678/validated-capillary-electrophoretic-method-for-the-enantiomeric-quality-control-of-r-praziquantel
#12
Zoltán-István Szabó, Réka Gál, Levente Szőcs, Róbert Ludmerczki, Daniela-Lucia Muntean, Béla Noszál, Gergő Tóth
The enantiomers of praziquantel, the drug of choice in schistosomiasis, were separated by electrokinetic chromatography with cyclodextrins. Nine anionic cyclodextrins were screened for their ability to discriminate between the uncharged enantiomers. Seven investigated selectors presented chiral interactions with the enantiomers, these cases being interpreted in terms of stability constants and complex mobilities. The best results were delivered by sulfated-β-cyclodextrin, where quasi-equal stability constants were accompanied by extreme selectivity values and was explained on the basis of highly different mobilities of the transient diastereomeric complexes...
February 21, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28221388/synthesis-of-c6-modified-%C3%AE-c-galcer-analogues-as-mouse-and-human-inkt-cell-agonists
#13
Joren Guillaume, Toshiyuki Seki, Tine Decruy, Koen Venken, Dirk Elewaut, Moriya Tsuji, Serge Van Calenbergh
α-GalCer analogues that combine known Th1 polarizing C6''-modifications with a C-glycosidic linkage were synthesized. We employed a protecting group strategy that allowed the preparation of both saturated and unsaturated derivatives with variable C6''-substituents. Selected analogues demonstrate promising activity in mice. Interestingly, the introduction of a 6''-O-pyridinylcarbamoyl substituent to α-C-GalCer restores its antigenicity in human iNKT cells.
February 21, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28221385/ir-spectroscopic-investigations-of-chemical-and-photochemical-reactions-on-metal-oxides-bridging-the-materials-gap
#14
REVIEW
Yuemin Wang, Christof Wöll
In this review, we highlight recent progress (2008-2016) in infrared reflection absorption spectroscopy (IRRAS) studies on oxide powders achieved by using different types of metal oxide single crystals as reference systems. Precise polarization- and azimuth-dependent IRRAS data recorded for single crystal substrates has allowed for fundamental insights into the surface chemistry and photochemistry of numerous probe molecules on various surfaces exposed by three very important metal oxides (ZnO, TiO2, and CeO2)...
February 21, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28221358/ionic-solutions-of-two-dimensional-materials
#15
Patrick L Cullen, Kathleen M Cox, Mohammed K Bin Subhan, Loren Picco, Oliver D Payton, David J Buckley, Thomas S Miller, Stephen A Hodge, Neal T Skipper, Vasiliki Tileli, Christopher A Howard
Strategies for forming liquid dispersions of nanomaterials typically focus on retarding reaggregation, for example via surface modification, as opposed to promoting the thermodynamically driven dissolution common for molecule-sized species. Here we demonstrate the true dissolution of a wide range of important 2D nanomaterials by forming layered material salts that spontaneously dissolve in polar solvents yielding ionic solutions. The benign dissolution advantageously maintains the morphology of the starting material, is stable against reaggregation and can achieve solutions containing exclusively individualized monolayers...
March 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28221353/from-helical-to-planar-chirality-by-on-surface-chemistry
#16
Oleksandr Stetsovych, Martin Švec, Jaroslav Vacek, Jana Vacek Chocholoušová, Andrej Jančařík, Jiří Rybáček, Krzysztof Kosmider, Irena G Stará, Pavel Jelínek, Ivo Starý
The chirality of molecular structures is paramount in many phenomena, including enantioselective reactions, molecular self-assembly, biological processes and light or electron-spin polarization. Flat prochiral molecules, which are achiral in the gas phase or solution, can exhibit adsorption-induced chirality when deposited on surfaces. The whole array of such molecular adsorbates is naturally racemic as spontaneous global mirror-symmetry breaking is disfavoured. Here we demonstrate a chemical method of obtaining flat prochiral molecules adsorbed on the solid achiral surface in such a way that a specific adsorbate handedness globally dominates...
March 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28221344/chemoproteomic-profiling-and-discovery-of-protein-electrophiles-in-human-cells
#17
Megan L Matthews, Lin He, Benjamin D Horning, Erika J Olson, Bruno E Correia, John R Yates, Philip E Dawson, Benjamin F Cravatt
Activity-based protein profiling (ABPP) serves as a chemical proteomic platform to discover and characterize functional amino acids in proteins on the basis of their enhanced reactivity towards small-molecule probes. This approach, to date, has mainly targeted nucleophilic functional groups, such as the side chains of serine and cysteine, using electrophilic probes. Here we show that 'reverse-polarity' (RP)-ABPP using clickable, nucleophilic hydrazine probes can capture and identify protein-bound electrophiles in cells...
March 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28221162/antiferromagnetic-spin-cantings-as-a-driving-force-of-ferroelectricity-in-multiferroic-cu-sub-2-sub-oseo-sub-3-sub
#18
Viacheslav Chizhikov, V Dmitrienko
Ferroelectric properties of cubic chiral magnet Cu<sub>2</sub>OSeO<sub>3</sub> can emerge due to the spin noncollinearity induced by antiferromagnetic cantings. The cantings are the result of the Dzyaloshinskii-Moriya interaction and in many ways similar to the ferromagnetic cantings in weak ferromagnets. An expression for the local electric polarization is derived, including terms with gradients of magnetization <b>M</b>(<b>r</b>). When averaged over the crystal the electric polarization has a non-vanishing part associated with the anisotropy of the crystal point group 23...
February 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28221047/excited-state-proton-transfer-in-indigo
#19
Joao Pina, Daniela Santos Sarmento, Marco Accoto, Pier Luigi Gentili, Luigi Vaccaro, Adelino M Galvão, J Sérgio Seixas de Melo
Excited state proton transfer (ESPT) in Indigo (Ind) and its mono hexyl-substituted derivative (NHxInd) in solution was investigated experimentally as a function of solvent viscosity, polarity and temperature, and theoretically by time-dependent DFT (TDDFT) calculations. Although a single emission band is observed, the fluorescence decays (collected at different wavelengths along the emission band using time-correlated single photon counting (TCSPC)) are bi-exponential, with two identical decay times but different pre-exponential factors, consistent with the existence of excited state keto and enol species...
February 21, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28221022/quantitative-13c-traces-of-glucose-fate-in-hepatitis-b-virus-infected-hepatocytes
#20
Qianfen Wan, Yulan Wang, Huiru Tang
Quantitative characterization of 13C-labeled metabolites is an important part of the stable isotope tracing method widely used in metabolic flux analysis. Due to long relaxation time and low sensitivity of 13C nuclei, direct measurement of 13C labeled metabolites using one dimensional 13C NMR often fails to meet the demand of metabolomics studies especially with large number of samples and metabolites having low abundance. Although HSQC-based 2D NMR methods have improved sensitivity with inversion detection, they are time-consuming thus unsuitable for high-throughput absolute quantification of 13C-labeled metabolites...
February 21, 2017: Analytical Chemistry
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