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https://www.readbyqxmd.com/read/28102680/ionicity-of-protic-ionic-liquid-quantitative-measurement-by-spectroscopic-methods
#1
Minming Shen, Yuyang Zhang, Kaizhou Chen, Siying Che, Jia Yao, Haoran Li
The ionicity value, which is a key property of protic ionic liquids, was obtained by the attenuated total reflection Fourier transform infrared spectroscopy and nuclear magnetic resonance respectively for a protic ionic liquid: n-propylammonium acetate. The method of potentiometric titration is found not suitable for such kind of ionic liquid as the ∆pKa of the compositing acid and base is relatively small. In the IR spectrum, molecular species can be directly observed in the range 1200-1800 cm-1, and the ratio of ionic and molecular species can be quantitatively calculated by the area of characteristic absorption peaks calibrated by standard curve from NaAc/HAc solutions...
January 19, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28102396/zinc-sparks-induce-physiochemical-changes-in-the-egg-zona-pellucida-that-prevent-polyspermy
#2
Emily L Que, Francesca E Duncan, Amanda R Bayer, Steven J Philips, Eric W Roth, Reiner Bleher, Sophie C Gleber, Stefan Vogt, Teresa K Woodruff, Thomas V O'Halloran
During fertilization or chemically-induced egg activation, the mouse egg releases billions of zinc atoms in brief bursts known as 'zinc sparks.' The zona pellucida (ZP), a glycoprotein matrix surrounding the egg, is the first structure zinc ions encounter as they diffuse away from the plasma membrane. Following fertilization, the ZP undergoes changes described as 'hardening', which prevent multiple sperm from fertilizing the egg and thereby establish a block to polyspermy. A major event in zona hardening is cleavage of ZP2 proteins by ovastacin; however, the overall physiochemical changes contributing to zona hardening are not well understood...
January 19, 2017: Integrative Biology: Quantitative Biosciences From Nano to Macro
https://www.readbyqxmd.com/read/28100297/transcriptional-analysis-of-mating-and-pre-infection-stages-of-the-anther-smut-microbotryum-lychnidis-dioicae
#3
Su San Toh, Zehua Chen, David J Schultz, Christina A Cuomo, Michael H Perlin
Microbotryum lychnidis-dioicae is an obligate biotrophic parasite of the wildflower species, Silene latifolia. This dikaryotic fungus, commonly known as an anther smut, requires that haploid, yeast-like sporidia of opposite mating types fuse and differentiate into dikaryotic hyphae that penetrate host tissue as part of the fungal lifecycle. Mating occurs under conditions of cool temperatures and limited nutrients. Further development requires host cues or chemical mimics, including a variety of lipids, e.g...
January 17, 2017: Microbiology
https://www.readbyqxmd.com/read/28099024/surface-interactions-and-confinement-of-methane-a-high-pressure-magic-angle-spinning-nmr-and-computational-chemistry-study
#4
Salim Ok, David W Hoyt, Amity Andersen, Julie Sheets, Susan A Welch, David R Cole, Karl Todd Mueller, Nancy M Washton
Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nano-porous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) were observed with 13C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed non-porous, 12 nm particle size silica and a mesoporous silica with 200 nm particle size and 4 nm average pore diameter...
January 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28098463/absolute-configuration-of-native-oligomeric-proanthocyanidins-with-dentin-biomodification-potency
#5
Joo-Won Nam, Rasika S Phansalkar, David C Lankin, James B McAlpine, Ariene A Leme-Kraus, Cristina M P Vidal, Li-She Gan, Ana Bedran-Russo, Shao-Nong Chen, Guido F Pauli
The structurally complex oligomeric proanthocyanidins (OPACs) are promising biomimetic agents, capable of strengthening the macromolecular backbone of teeth via intermolecular and intermicrofibrillar cross-linking. This study establishes analytical methods capable of determining the absolute configuration of the catechin-type monomeric units of underivatized OPACs. This preserves the capacity of their biological evaluation, aimed at understanding the inevitably stereospecific interactions between the OPACs and dentin collagen...
January 18, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28095496/opportunities-for-integrated-ecological-analysis-across-inland-australia-with-standardised-data-from-ausplots-rangelands
#6
Greg R Guerin, Ben Sparrow, Andrew Tokmakoff, Anita Smyth, Emrys Leitch, Zdravko Baruch, Andrew J Lowe
Australian rangelands ecosystems cover 81% of the continent but are understudied and continental-scale research has been limited in part by a lack of precise data that are standardised between jurisdictions. We present a new dataset from AusPlots Rangelands that enables integrative rangelands analysis due to its geographic scope and standardised methodology. The method provides data on vegetation and soils, enabling comparison of a suite of metrics including fractional vegetation cover, basal area, and species richness, diversity, and composition...
2017: PloS One
https://www.readbyqxmd.com/read/28095036/differentiation-of-clear-cell-renal-cell-carcinoma-from-other-renal-cortical-tumors-by-use-of-a-quantitative-multiparametric-mri-approach
#7
Andreas M Hötker, Yousef Mazaheri, Andreas Wibmer, Christoph A Karlo, Junting Zheng, Chaya S Moskowitz, Satish K Tickoo, Paul Russo, Hedvig Hricak, Oguz Akin
OBJECTIVE: The purpose of this study was to develop a quantitative multiparametric MRI approach to differentiating clear cell renal cell carcinoma (RCC) from other renal cortical tumors. MATERIALS AND METHODS: This retrospective study included 119 patients with 124 histopathologically confirmed renal cortical tumors who underwent preoperative MRI including DWI, contrast-enhanced, and chemical-shift sequences before nephrectomy. Two radiologists independently assessed each tumor volumetrically, and apparent diffusion coefficient values, parameters from multiphasic contrast-enhanced MRI (peak enhancement, upslope, downslope, AUC), and chemical-shift indexes were calculated...
January 17, 2017: AJR. American Journal of Roentgenology
https://www.readbyqxmd.com/read/28094816/methylation-specific-targeting-of-a-chromatin-remodeling-complex-from-sponges-to-humans
#8
Jason M Cramer, Deborah Pohlmann, Fernando Gomez, Leslie Mark, Benjamin Kornegay, Chelsea Hall, Edhriz Siraliev-Perez, Ninad M Walavalkar, M Jeannette Sperlazza, Stephanie Bilinovich, Jeremy W Prokop, April L Hill, David C Williams
DNA cytosine methylation and methyl-cytosine binding domain (MBD) containing proteins are found throughout all vertebrate species studied to date. However, both the presence of DNA methylation and pattern of methylation varies among invertebrate species. Invertebrates generally have only a single MBD protein, MBD2/3, that does not always contain appropriate residues for selectively binding methylated DNA. Therefore, we sought to determine whether sponges, one of the most ancient extant metazoan lineages, possess an MBD2/3 capable of recognizing methylated DNA and recruiting the associated nucleosome remodeling and deacetylase (NuRD) complex...
January 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28093910/structural-and-spectral-properties-of-photochromic-diarylethenes-the-size-effect-of-the-ethene-bridge
#9
Andrey G Lvov, Alexey M Kavun, Vadim V Kachala, Yulia V Nelyubina, Anatoly V Metelitsa, Valerii Z Shirinian
The effect of the size of the ethene bridge on the structural and spectral properties of photochromic diarylethenes, which remains a poorly understood phenomenon, was studied as applied to diarylethenes containing unsymmetrical (cyclohexenone and cyclopentenone) and symmetrical (cyclohexene and cyclopentene) ethene bridges. Thiophene, oxazole, and imidazole derivatives were used as aryl moieties. An increase in the size of the ethene bridge in the cycloalkenone series was found to be accompanied by a hypsochromic shift of the absorption maximum of the photoinduced form, whereas no difference was found for cycloalkenes...
January 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28093831/light-controlled-reversible-modulation-of-frontier-molecular-orbital-energy-levels-in-trifluoromethylated-diarylethenes
#10
Martin Herder, Fabian Eisenreich, Aurelio Bonasera, Anna Grafl, Lutz Grubert, Michael Pätzel, Jutta Schwarz, Stefan Hecht
Among bistable photochromic molecules diarylethenes (DAEs) possess the distinct feature that upon photoisomerization they undergo a large modulation of their π-electronic system, accompanied by a marked shift of the HOMO/LUMO energies and hence oxidation/reduction potentials. In order to exploit such photoswitchable systems it is important to precisely adjust the absolute position of their HOMO and LUMO levels and to maximize the extent of the photoinduced shifts of these energy levels. Here, we present a comprehensive study detailing how variation of the substitution pattern of DAE compounds, in particular using strongly electron-accepting and chemically stable trifluoromethyl groups either in the periphery or at the reactive carbon atoms, allows for the precise tuning of frontier molecular orbital levels over a broad energy range and the generation of photoinduced shifts of more than 1 eV...
January 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28093471/interactions-studies-between-periplasmic-cytochromes-provide-insights-on-extracellular-electron-transfer-pathways-of-geobacter-sulfurreducens
#11
Ana P Fernandes, Tiago C Nunes, Catarina M Paquete, Carlos A Salgueiro
Geobacter bacteria usually prevail among other microorganisms in soils and sediments where Fe(III) reduction has a central role. This reduction is achieved by extracellular electron transfer, where the electrons are exported from the interior of the cell to the surrounding environment. Periplasmic cytochromes play an important role in establishing an interface between inner and outer membrane electron transfer components. In addition, periplasmic cytochromes, in particular nanowire cytochromes that contain at least 12 haem groups, have been proposed to play a role in electron storage in conditions of environmental lack of electron acceptors...
January 16, 2017: Biochemical Journal
https://www.readbyqxmd.com/read/28092409/quantification-of-brown-and-white-adipose-tissue-based-on-gaussian-mixture-model-using-water-fat-and-t2-mri-in-adolescents
#12
Steve C N Hui, Jacky K L Ko, Teng Zhang, Lin Shi, David K W Yeung, Defeng Wang, Queenie Chan, Winnie C W Chu
PURPOSE: To develop a technique for the separation and quantification of brown adipose tissue (BAT) and white adipose tissue (WAT) using fat fraction and T2* intensity based on the Gaussian mixture model (GMM). MATERIALS AND METHODS: Chemical-shift water-fat and T2* images were acquired at the neck, supraclavicular, interscapular, and paravertebral regions in 24 volunteers (Obese: n = 12, female/male = 6/6, body mass index [BMI] = 31.3 ± 2.3 kg/m(2) , age = 16...
January 16, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28092038/nmr-chemical-shift-mapping-of-sh2-peptide-interactions
#13
Marissa A McKercher, Deborah S Wuttke
Heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) experiments offer a rapid and high resolution approach to gaining binding and conformational insights into a protein-peptide interaction. By tracking (1)H and (15)N chemical shift changes over the course of a peptide titration into isotopically labeled protein, amide NH pairs of amino acids whose chemical environment changes upon peptide binding can be identified. When mapped onto a structure of the protein, this approach can identify the peptide-binding interface or regions undergoing conformation changes within a protein upon ligand binding...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28091999/porous-nano-cerium-oxide-wood-chip-biochar-composites-for-aqueous-levofloxacin-removal-and-sorption-mechanism-insights
#14
Shengze Yi, Yuanyuan Sun, Xin Hu, Hongxia Xu, Bin Gao, Jichun Wu
The adsorption removal of levofloxacin (LEV), a widely used fluoroquinolone antibiotic, by using the biochars derived from the pyrolysis of pine wood chip pretreated with cerium trichloride was investigated through batch sorption experiments and multiple characterization techniques. The differences in the basic physicochemical properties between Ce-impregnated biochars and the pristine biochars were confirmed by the analysis of elemental compositions, specific surface areas, energy dispersive spectrometry, X-ray diffraction, and thermo-gravimetry...
January 14, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28091672/a-rapid-way-to-discover-nonstandard-macrocyclic-peptide-modulators-of-drug-targets
#15
Toby Passioura, Hiroaki Suga
Studies of the fundamental nature of RNA catalysis and the potential mechanism of a shift from the "RNA world" to proteinaceous life lead us to identify a set of ribozymes (flexizymes) capable of promiscuous tRNA acylation. Whilst theoretically and mechanistically interesting in their own right, flexizymes have turned out to have immense practical value for the simple synthesis of tRNAs acylated with unusual amino acids, which in turn can be used for the ribosomal synthesis of peptides containing non-canonical residues...
January 16, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28091517/unraveling-the-enhanced-oxygen-vacancy-formation-in-complex-oxides-during-annealing-and-growth
#16
Felix V E Hensling, Chencheng Xu, Felix Gunkel, Regina Dittmann
The reduction of oxides during annealing and growth in low pressure processes is a widely known problem. We hence investigate the influence of mere annealing and of growth in vacuum systems to shed light on the reasons behind the reduction of perovskites. When comparing the existing literature regarding the reduction of the perovskite model material SrTiO3 it is conspicuous that one finds different oxygen pressures required to achieve reduction for vacuum annealing and for chemically controlled reducing atmospheres...
January 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28090435/-13-c-metabolomics-nmr-and-iroa-for-unknown-identification
#17
Chaevien S Clendinen, Gregory S Stupp, Bing Wang, Timothy J Garrett, Arthur S Edison
ABSTRACT BACKGROUND: Isotopic Ratio Outlier Analysis (IROA) is an untargeted metabolomics method that uses stable isotopic labeling and LC-HRMS for identification and relative quantification of metabolites in a biological sample under varying experimental conditions. OBJECTIVE: We demonstrate a method using high-sensitivity (13)C NMR to identify an unknown metabolite isolated from fractionated material from an IROA LC-HRMS experiment. METHODS: IROA samples from the nematode Caenorhabditis elegans were fractionated using LC-HRMS using 5 repeated injections and collecting 30 sec fractions...
August 2016: Current Metabolomics
https://www.readbyqxmd.com/read/28088866/a-combined-experimental-and-computational-study-on-the-unimolecular-decomposition-of-jp-8-jet-fuel-surrogates-ii-n-dodecane-n-c12h26
#18
Long Zhao, Tao Yang, Ralf I Kaiser, Tyler Patrick Troy, Musahid Ahmed, Joao Marcelo Ribeiro, Daniel Belisario-Lara, Alexander Moiseevich Mebel
We investigated temperature-dependent products in the pyrolysis of helium-seeded n-dodecane, which represents a surrogate of the n-alkane fraction of Jet Propellant-8 (JP-8) aviation fuel. The experiments were performed in a high temperature chemical reactor over a temperature range of 1,200 K to 1,600 K at a pressure of 600 Torr, with in situ identification of the nascent products in a supersonic molecular beam using single photon vacuum ultraviolet (VUV) photoionization coupled with the analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF)...
January 16, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28088860/a-combined-experimental-and-computational-study-on-the-unimolecular-decomposition-of-jp-8-jet-fuel-surrogates-i-n-decane-n-c10h22
#19
Long Zhao, Tao Yang, Ralf I Kaiser, Tyler Patrick Troy, Musahid Ahmed, Daniel Belisario-Lara, Joao Marcelo Ribeiro, Alexander Moiseevich Mebel
Exploiting a high temperature chemical reactor, we explored the pyrolysis of helium-seeded n-decane as a surrogate of the n-alkane fraction of Jet Propellant-8 (JP-8) over a temperature range of 1,100 K to 1,600 K at a pressure of 600 Torr. The nascent products were identified in situ in a supersonic molecular beam via single photon vacuum ultraviolet (VUV) photoionization coupled with a mass spectroscopic analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF). Our studies probe, for the first time, the initial reaction products formed in the decomposition of n-decane - including radicals and thermally labile closed-shell species effectively excluding mass growth processes...
January 16, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28079219/internal-dynamics-in-helical-molecules-studied-by-x-ray-diffraction-nmr-spectroscopy-and-dft-calculations
#20
Martin Dračínský, Jan Storch, Vladimír Církva, Ivana Císařová, Jan Sýkora
The conformational behaviour of a prototype helical molecule, [6]helicene, and its derivatives was studied in solution and the solid state. Available crystal structures of [6]helicene revealed surprisingly large flexibility of this molecule and variable-temperature NMR experiments provided unusual temperature dependence of chemical shifts of hydrogen, carbon and fluorine atoms in the peripheral aromatic rings of [6]helicene and tetrafluoro[6]helicene. These chemical shift changes were interpreted as a consequence of the helicene 'pitch' opening with elevated temperature, and the experimental data were corroborated by DFT calculations of the chemical shift dependence on the helicene conformation and by variable-temperature DFT molecular dynamics simulations...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
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