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https://www.readbyqxmd.com/read/28535460/a-synchrotron-infrared-absorption-study-of-pressure-induced-polymerization-of-acrylamide
#1
Himal Bhatt, M N Deo
The hydrogen bonded dimeric structure of the model amide based molecular crystal acrylamide has been investigated under pressure using micro-spectroscopy, employing synchrotron infrared radiation up to 24GPa at room temperature. The high pressure spectra indicate systematic evolution of new features above 4GPa, which have been identified to be due to the emergence of a polymeric phase. The polymerization gets completed up to 16.8GPa and the observed changes are found to be irreversible upon the release of pressure...
May 1, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28524209/understanding-the-biomimetic-properties-of-gallium-in-pseudomonas-aeruginosa-an-xas-and-xps-study
#2
F Porcaro, C Bonchi, A Ugolini, E Frangipani, G Polzonetti, P Visca, C Meneghini, C Battocchio
Pyochelin (PCH) is a siderophore (extracellular chelator) produced by the pathogenic bacterium Pseudomonas aeruginosa (PAO). PCH is implicated in iron (Fe(3+)) transport to PAO, and is crucial for its metabolism and pathogenicity. Due to the chemical similarity with Fe(3+), gallium (Ga(3+)) interferes with vital iron-dependent processes in bacterial cells, thereby opening new perspectives for the design of specific metal-based antibacterial drugs. However, the structural basis for the Fe(3+)-mimetic properties of Ga(3+) complexed with the PCH siderophore is still lacking...
May 19, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28521096/photoionization-efficiencies-of-five-polycyclic-aromatic-hydrocarbons
#3
K Olof Johansson, Matthew F Campbell, Paolo Elvati, Paul E Schrader, Judit Zádor, Nicole K Richards-Henderson, Kevin R Wilson, Angela Violi, Hope A Michelsen
We have measured photoionization-efficiency curves for pyrene, fluoranthene, chrysene, perylene, and coronene in the photon-energy range 7.5-10.2 eV and derived their photoionization cross-section curves in this energy range. All measurements were performed using tunable vacuum ultraviolet (VUV) radiation generated at the Advanced Light Source synchrotron at Lawrence Berkeley National Laboratory. The VUV radiation was used for photoionization and detection was performed using a time-of-flight mass spectrometer...
May 18, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28512575/new-leads-for-fragment-based-design-of-rhenium-technetium-radiopharmaceutical-agents
#4
Alice Brink, John R Helliwell
Multiple possibilities for the coordination of fac-[Re(CO)3(H2O)3](+) to a protein have been determined and include binding to Asp, Glu, Arg and His amino-acid residues as well as to the C-terminal carboxylate in the vicinity of Leu and Pro. The large number of rhenium metal complex binding sites that have been identified on specific residues thereby allow increased target identification for the design of future radiopharmaceuticals. The core experimental concept involved the use of state-of-art tuneable synchrotron radiation at the Diamond Light Source to optimize the rhenium anomalous dispersion signal to a large value (f'' of 12...
May 1, 2017: IUCrJ
https://www.readbyqxmd.com/read/28511668/structural-similarities-and-functional-differences-clarify-evolutionary-relationships-between-trna-healing-enzymes-and-the-myelin-enzyme-cnpase
#5
Gopinath Muruganandam, Arne Raasakka, Matti Myllykoski, Inari Kursula, Petri Kursula
BACKGROUND: Eukaryotic tRNA splicing is an essential process in the transformation of a primary tRNA transcript into a mature functional tRNA molecule. 5'-phosphate ligation involves two steps: a healing reaction catalyzed by polynucleotide kinase (PNK) in association with cyclic phosphodiesterase (CPDase), and a sealing reaction catalyzed by an RNA ligase. The enzymes that catalyze tRNA healing in yeast and higher eukaryotes are homologous to the members of the 2H phosphoesterase superfamily, in particular to the vertebrate myelin enzyme 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase)...
May 16, 2017: BMC Biochemistry
https://www.readbyqxmd.com/read/28511007/thicker-lamellae-and-higher-crystallinity-of-poly-lactic-acid-via-applying-shear-flow-and-pressure-and-adding-poly-ethylene-glycol
#6
Jia-Feng Ru, Shu-Gui Yang, Jun Lei, Zhong-Ming Li
In this work, we explored the crystallization of Poly(lactic acid) (PLA) blended with poly(ethylene glycol) (PEG) under two inevitable processing fields (i.e., flow and pressure) that coexist in almost all processing for the first time. Here, the PEG was incorporated into PLA as a molecular chain activity promoter to induce PLA crystallization. A home-made pressuring and shearing device (PSD) was utilized to prepare samples and necessary characterization methods, such as differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and synchrotron radiation, were used to investigated the joint effects of PEG, pressure and shear flow on the crystallization behaviors and morphologies of PLA/PEG samples...
May 16, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28508574/isomer-selective-generation-and-spectroscopic-characterization-of-picolyl-radicals
#7
Engelbert Reusch, Fabian Holzmeier, Philipp Constantinidis, Patrick Hemberger, Ingo Fischer
Nitrogen-containing resonance-stabilized radicals like picolyl are important in combustion chemistry and astrochemistry. They have only been scarcely studied, because an isomer-selective generation is often difficult. Here we present threshold photoelectron spectra of three picolyl radical isomers, C6H6N, using synchrotron radiation. The radicals were selectively generated by flash pyrolysis from aminomethylpyridine precursors via deamination. Ionization energies of 7.70 eV, 7.59 eV and 8.01 eV are determined for 2-, 3- and 4-picolyl, respectively...
May 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28504798/a-vacuum-ultraviolet-photoionization-study-on-high-temperature-decomposition-of-jp-10-exo-tetrahydrodicyclopentadiene
#8
Long Zhao, Tao Yang, Ralf I Kaiser, Tyler P Troy, Bo Xu, Musahid Ahmed, Juan Alarcon, Daniel Belisario-Lara, Alexander M Mebel, Yan Zhang, Chuangchuang Cao, Jiabiao Zou
Two sets of experiments were performed to unravel the high-temperature pyrolysis of tricyclo[5.2.1.0(2,6)] decane (JP-10) exploiting high-temperature reactors over a temperature range of 1100 K to 1600 K, Advanced Light Source (ALS), and 927 K to 1083 K, National Synchrotron Radiation Laboratory (NSRL), with residence times of a few tens of microseconds (ALS) to typically 144 ms (NSRL). The products were identified in situ in supersonic molecular beams via single photon vacuum ultraviolet (VUV) photoionization coupled with mass spectroscopic detection in a reflectron time-of-flight mass spectrometer (ReTOF)...
May 15, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28504761/high-reflectance-magnetron-sputtered-scandium-based-x-ray-multilayer-mirrors-for-the-water-window
#9
C Burcklen, S de Rossi, E Meltchakov, D Dennetière, B Capitanio, F Polack, F Delmotte
We present an experimental comparison of several Sc-based short period multilayer mirrors including Cr/Sc with B<sub>4</sub>C barrier layers and CrN<sub>x</sub>/Sc, and we propose a new material combination that provides high reflectance in the water window domain. Multilayer samples with period thickness in the range 1.5-1.7 nm have been deposited by magnetron sputtering and characterized by x-ray reflectometry with a Cu-Kα source and with synchrotron radiation near the Sc-L<sub>2,3</sub> edge...
May 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28504758/pulse-picker-for-synchrotron-radiation-driven-by-a-surface-acoustic-wave
#10
Simone Vadilonga, Ivo Zizak, Dmitry Roshchupkin, Andrei Petsiuk, Igor Dolbnya, Kawal Sawhney, Alexei Erko
A functional test for a pulse picker for synchrotron radiation was performed at Diamond Light Source. The purpose of a pulse picker is to select which pulse from the synchrotron hybrid-mode bunch pattern reaches the experiment. In the present work, the Bragg reflection on a Si/B<sub>4</sub>C multilayer was modified using surface acoustic wave (SAW) trains. Diffraction on the SAW alters the direction of the x rays and it can be used to modulate the intensity of the x rays that reach the experimental chamber...
May 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/28503692/time-resolved-measurements-of-product-formation-in-the-low-temperature-550-675-k-oxidation-of-neopentane-a-probe-to-investigate-chain-branching-mechanism
#11
Arkke J Eskola, Ivan O Antonov, Leonid Sheps, John D Savee, David L Osborn, Craig A Taatjes
Product formation, in particular ketohydroperoxide formation and decomposition, were investigated in time-resolved, Cl-atom initiated neopentane oxidation experiments in the temperature range 550-675 K using a photoionization time-of-flight mass spectrometer. Ionization light was provided either by Advanced Light Source tunable synchrotron radiation or ∼10.2 eV fixed energy radiation from a H2-discharge lamp. Experiments were performed both at 1-2 atm pressure using a high-pressure reactor and also at ∼9 Torr pressure employing a low-pressure reactor for comparison...
May 15, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28501721/cortical-bone-elasticity-measured-by-resonant-ultrasound-spectroscopy-is-not-altered-by-defatting-and-synchrotron-x-ray-imaging
#12
X Cai, L Peralta, A Giron, L Helfen, C Olivier, F Peyrin, P Laugier, Q Grimal
In the study of mechanical properties of human bone, specimens may be defatted before experiments to prevent contamination and the risk of infections. High energy synchrotron radiation micro-computed tomography (SR-μCT) is a popular technique to study bone microstructure. However, little is known about the effects of defatting or irradiation during SR-μCT imaging on different elastic coefficients including shear and longitudinal moduli in different anatomical directions. In this work, these effects are evaluated on a set of 24 samples using resonant ultrasound spectroscopy (RUS), which allows one to accurately measure the complete set of elastic coefficients of cortical bone non destructively...
May 6, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28501440/classification-of-microcrystalline-celluloses-via-structures-of-individual-particles-measured-by-synchrotron-radiation-x-ray-micro-computed-tomography
#13
Longwei Fang, Xianzhen Yin, Li Wu, Yaping He, Yuanzhi He, Wei Qin, Fanyue Meng, Peter York, Xu Xu, Jiwen Zhang
Microcrystalline cellulose (MCC) is one of the most important excipients due to its outstanding binding and tableting properties. Owing to the absence of high resolution characterization techniques at the single particle scale, 3D (three dimension) microstructure of MCC and its effects on formulation performance remain unexamined. The aim of this work was to establish a methodology for single particles of MCC type 102 based on synchrotron radiation X-ray micro computed tomography (SR-μCT), principal component analysis (PCA) and partial least square discriminant analysis (PLSDA)...
May 10, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28500280/visualization-of-a-mammalian-mitochondrion-by-coherent-x-ray-diffractive-imaging
#14
Yoonhee Kim, Chan Kim, Ou Young Kwon, Daewoong Nam, Sang Soo Kim, Jae Hyun Park, Sunam Kim, Marcus Gallagher-Jones, Yoshiki Kohmura, Tetsuya Ishikawa, Changyong Song, Giyoong Tae, Do Young Noh
We report a three dimensional (3D) quantitative visualization of a mammalian mitochondrion by coherent x-ray diffractive imaging (CXDI) using synchrotron radiation. The internal structures of a mitochondrion from a mouse embryonic fibroblast cell line (NIH3T3) were visualized by tomographic imaging at approximately 60 nm resolution without the need for sectioning or staining. The overall structure consisted of a high electron density region, composed of the outer and inner membranes and the cristae cluster, which enclosed the lower density mitochondrial matrix...
May 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28497291/two-early-eudicot-fossil-flowers-from-the-kamikitaba-assemblage-coniacian-late-cretaceous-in-northeastern-japan
#15
Masamichi Takahashi, Patrick S Herendeen, Xianghui Xiao
Two new fossil taxa referable to the basal eudicot grade are described from the Kamikitaba locality (ca. 89 MYBP, early Coniacian: Late Cretaceous) of the Futaba Group in Japan. These charcoalified mesofossils exhibit well-preserved three-dimensional structure and were analyzed using synchrotron-radiation X-ray microtomography to document their composition and internal structure. Cathiaria japonica sp. nov. is represented by infructescence segments that consist of an axis bearing three to four fruits. The capsular fruits are sessile and dehiscent and consist of a gynoecium subtended by a bract...
May 11, 2017: Journal of Plant Research
https://www.readbyqxmd.com/read/28492651/the-influence-of-carbon-concentration-on-the-electronic-structure-and-magnetic-properties-of-carbon-implanted-zno-thin-films
#16
K Saravanan, G Jayalakshmi, Sharat Chandra, B K Panigrahi, R Krishnan, B Sundaravel, S Annapoorani, D K Shukla, P Rajput, D Kanjilal
The influence of carbon concentration on the electronic and magnetic properties of C-implanted ZnO thin films has been studied using synchrotron radiation based X-ray absorption spectroscopic techniques and vibrating sample magnetometer measurements. 20 keV carbon ions were implanted in ZnO films with different fluences (2 × 10(16), 4 × 10(16) and 6 × 10(16) ions per cm(2)). The pristine ZnO film shows diamagnetic behaviour while the C-implanted films exhibit room temperature ferromagnetism. Our first-principles calculations based on density functional theory show an appreciable magnetic moment only when the implanted C atom sits either in the O-site (2 μB) or in the interstitial position (1...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28490711/purification-crystallization-and-x-ray-diffraction-study-of-the-c-terminal-domain-of-human-herpesvirus-6a-immediate-early-protein-2
#17
Junjie Wang, Mitsuhiro Nishimura, Aika Wakata, Yasuko Mori
Human herpesvirus 6A (HHV-6A) starts its replication cycle following the action of immediate early proteins that transactivate viral promoters. Immediate early protein 2 (IE2) of HHV-6A is a 1500 amino acid polypeptide with a C-terminal region that is conserved among beta-herpesvirus subfamily members. In this study, a structural domain in the homologous C-terminal region was subjected to secondary structure prediction, and residues 1324-1500 were subsequently designated as the C-terminal domain of IE2 (IE2-CTD)...
April 7, 2017: Kobe Journal of Medical Sciences
https://www.readbyqxmd.com/read/28486809/crystallographic-structure-determination-of-both-5-6-and-6-6-isomers-of-lithium-ion-containing-dipheylmethano-60-fullerene
#18
Hiroshi Okada, Hiroki Kawakami, Shinobu Aoyagi, Yutaka Matsuo
Organic functionalization of lithium-ion-containing [60]fullerene, Li+@C60, was performed by using diphenyl(diazo)methane as a stable, readily available diazo compound to obtain lithium-ion-encapsulated [5,6]- and [6,6]-diphenylmethano[60]fullerenes, Li+@C61Ph2. The bis(trifluoromethanesulfonyl)imide (TFSI) salts of [5,6]- and [6,6]-Li+@C61Ph2 were successfully separated by using a cation exchange column with eluent containing LiTFSI. Improved separation protocol and high crystallinity of ionic components in less polar solvents enabled separate crystallization of each isomer...
May 10, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28474019/direct-observation-of-active-material-interactions-in-flowable-electrodes-using-x-ray-tomography
#19
Kelsey B Hatzell, Jens Eller, Samantha L Morelly, Maureen H Tang, Nicolas J Alvarez, Yury Gogotsi
Understanding electrical percolation and charging mechanisms in electrochemically active biphasic flowable electrodes is critical for enabling scalable deionization (desalination) and energy storage. Flowable electrodes are dynamic material systems which store charge (remove ions) and have the ability to flow. This flow process can induce structural changes in the underlying material arrangement and result in transient and non-uniform material properties. Carbon-based suspensions are opaque, multi-phase, and three dimensional, and thus prior characterization of the structural properties has been limited to indirect methods (electrochemical and rheology)...
May 5, 2017: Faraday Discussions
https://www.readbyqxmd.com/read/28463472/ontogenetic-constraints-on-foraminiferal-test-construction
#20
Aude G M Caromel, Daniela N Schmidt, Emily J Rayfield
Developmental processes represent one of the main constraints on the generation of adult form. Determining how constructional and energetic demands operate throughout growth is es-sential to understanding fundamental growth rules and trade-offs that define the framework within which new species originate. In organisms producing spiral shells, coiling patterns can inform on the constructional constraints acting throughout development that dictated the diversification of forms within a group. Here, we use Synchrotron radiation X-Ray tomographic microscopy (SRXTM) reconstructions of eight planktic foraminifera repre-sentative of the major morphotypic groups to determine disparity of coiling patterns by measuring Raupian parameters...
May 2017: Evolution & Development
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