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https://www.readbyqxmd.com/read/28109035/competitive-benzyl-cation-transfer-proton-transfer-collision-induced-mass-spectrometric-fragmentation-of-protonated-n-n-dibenzylaniline
#1
Ge Ma, Gongye Liu, Shanshan Shen, Yunfeng Chai, Lei Yue, Shunping Zhao, Yuanjiang Pan
Collision-induced dissociation of protonated N,N-dibenzylaniline was investigated by electrospray tandem mass spectrometry. Various fragmentation pathways were dominated by benzyl cation and proton transfer. Benzyl cation transfers from the initial site (nitrogen) to benzylic phenyl or aniline phenyl ring. The benzyl cations transfer to the two different sites and both result in the benzene loss combined with 1,3-H shift. In addition, after the benzyl cation transfers to the benzylic phenyl ring, 1,2-H shift and 1,4-H shift proceed competitively to trigger the diphenylmethane loss and aniline loss respectively...
January 21, 2017: Journal of Mass Spectrometry: JMS
https://www.readbyqxmd.com/read/28108411/production-and-characterization-of-medium-chain-length-polyhydroxyalkanoates-copolymer-from-arctic-psychrotrophic-bacterium-pseudomonas-sp-pamc-28620
#2
Ganesan Sathiyanarayanan, Shashi Kant Bhatia, Hun-Suk Song, Jong-Min Jeon, Jun-Young Kim, Yoo Kyung Lee, Yun-Gon Kim, Yung-Hun Yang
Arctic psychrotrophic bacterium Pseudomonas sp. PAMC 28620 was found to produce a distinctive medium-chain-length polyhydroxyalkanoates (MCL-PHAs) copolymer when grown on structurally unrelated carbon sources including glycerol. The maximum MCL-PHAs copolymer yield was obtained about 52.18±4.12% from 7.95±0.66g/L of biomass at 144h of fermentation when 3% glycerol was used as sole carbon and energy source during the laboratory-scale bioreactor process. Characterization of the copolymer was carried out using fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC-MS), proton ((1)H) and carbon ((13)C) nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), differential scanning calorimeter (DSC) and thermo-gravimetric analysis (TGA)...
January 17, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28108101/development-of-a-high-resolution-voxelised-head-phantom-for-medical-physics-applications
#3
REVIEW
V Giacometti, S Guatelli, M Bazalova-Carter, A B Rosenfeld, R W Schulte
Computational anthropomorphic phantoms have become an important investigation tool for medical imaging and dosimetry for radiotherapy and radiation protection. The development of computational phantoms with realistic anatomical features contribute significantly to the development of novel methods in medical physics. For many applications, it is desirable that such computational phantoms have a real-world physical counterpart in order to verify the obtained results. In this work, we report the development of a voxelised phantom, the HIGH_RES_HEAD, modelling a paediatric head based on the commercial phantom 715-HN (CIRS)...
January 17, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28107949/a-microcalorimetry-study-on-the-oxidation-of-linoleic-acid-and-the-control-of-rancidity
#4
Nabil Haman, Andrea Romano, Mohammad Asaduzzaman, Giovanna Ferrentino, Franco Biasioli, Matteo Scampicchio
The oxidative deterioration of unsaturated lipids fatty acids is a great concern for the food industry as it is associated with the development of rancid off-odors and the reduction of food quality. This work describes the potential use of isothermal microcalorimetry to monitor the oxidation of linoleic acid, an important conjugated fatty acid responsible for the development of rancidity. The heat flow signal developed during the oxidation process reflects a multistep mechanism typical of radical chain reactions...
March 1, 2017: Talanta
https://www.readbyqxmd.com/read/28107633/binding-and-proton-blockage-by-amantadine-variants-of-the-influenza-m2wt-and-m2s31n-explained
#5
Christina Tzitzoglaki, Anna K Wright, Kathrin-Maria Freudenberger, Anja Hoffmann, Ian Tietjen, Ioannis Stylianakis, Felix Kolarov, David Fedida, Michaela Schmidtke, Guenter Gauglitz, Timothy A Cross, Antonios Kolocouris
While aminoadamantanes are well-established inhibitors of the influenza A M2 proton channel, the mechanisms by which they are rendered ineffective against M2S31N are unclear. Solid state NMR, isothermal titration calorimetry, electrophysiology, anti-viral assays and molecular dynamics simulations suggest stronger binding interactions for aminoadamantanes to M2WT compared to negligible or weak binding to M2S31N. This is due to reshaping of the M2pore when N31 is present, which in contrast to WT, leads: A) to the loss of the V27 pocket for the adamantyl cage and to a predominant orientation of the ligand's ammonium group toward the N-terminus and, B) to the lack of a helical kink upon ligand binding...
January 20, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28107554/inclusion-of-a-variable-rbe-into-proton-and-photon-plan-comparison-for-various-fractionation-schedules-in-prostate-radiation-therapy
#6
Jakob Ödén, Kjell Eriksson, Iuliana Toma-Dasu
PURPOSE: A constant relative biological effectiveness (RBE) of 1.1 is currently used in proton radiation therapy to account for the increased biological effectiveness compared to photon therapy. However, there is increasing evidence that proton RBE vary with the linear energy transfer (LET), the dose per fraction and the type of the tissue. Therefore, this study aims to evaluate the impact of disregarding variations in RBE when comparing proton and photon dose plans for prostate treatments for various fractionation schedules using published RBE models and several α/β assumptions...
January 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28107435/peptide-targeted-by-human-antibodies-associated-with-hiv-vaccine-associated-protection-assumes-a-dynamic-%C3%AE-helical-structure
#7
Mohammed S Aiyegbo, Evgeny Shmelkov, Lorenzo Dominguez, Michael Goger, Shibani Battacharya, Allan C deCamp, Peter B Gilbert, Phillip W Berman, Timothy Cardozo
The only evidence of vaccine-induced protection from HIV acquisition in humans was obtained in the RV144 HIV vaccine clinical trial. One immune correlate of risk in RV144 was observed to be higher titers of vaccine-induced antibodies (Abs) reacting with a 23-mer non-glycosylated peptide with the same amino acid sequence as a segment in the second variable (V2) loop of the MN strain of HIV. We used NMR to analyze the dynamic 3D structure of this peptide. Distance restraints between spatially proximate inter-residue protons were calculated from NOE cross peak intensities and used to constrain a thorough search of all possible conformations of the peptide...
2017: PloS One
https://www.readbyqxmd.com/read/28107257/perceived-stress-as-a-risk-factor-for-dyspepsia-a-register-based-cohort-study
#8
Ulrik Deding, Christian Torp-Pedersen, Henrik Bøggild
OBJECTIVE: Dyspepsia is a common condition and has a huge impact on quality of life and working capacity, but its causes are not well understood. An association between stress and dyspepsia has been debated for decades, but the issue has not been resolved. We examined the 3-year risk of redeeming a proton-pump inhibitor or an H2-receptor antagonist as a proxy of dyspepsia according to the level of perceived stress. PARTICIPANTS AND METHODS: Perceived stress was measured in a general health survey of 16 124 Danes aged older than 16 years of age in 2010 using Cohen's Perceived Stress Scale...
January 19, 2017: European Journal of Gastroenterology & Hepatology
https://www.readbyqxmd.com/read/28107011/delocalization-of-coherent-triplet-excitons-in-linear-rigid-rod-conjugated-oligomers
#9
Christian Hintze, Patrick Korf, Frank Degen, Friederike Schütze, Stefan Mecking, Ulrich E Steiner, Malte Drescher
In this work, the triplet state delocalization in a series of monodisperse oligo(p-phenyleneethynylene)s (OPEs) is studied by pulsed electron paramagnetic resonance (EPR) and pulsed electron nuclear double resonance (ENDOR) determining zero-field splitting, optical spin polarization, and proton hyperfine couplings. Neither the zero-field splitting parameters nor the optical spin polarization change significantly with OPE chain length, in contrast to the hyperfine coupling constants, which showed a systematic decrease with chain length n according to a 2/(1+n) decay law...
January 20, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28107009/nmr-and-computation-reveal-a-pressure-sensitive-folded-conformation-of-trp-cage
#10
Soichiro Kitazawa, Martin J Fossat, Scott A McCallum, Angel E Garcia, Catherine Ann Royer
Beyond defining the structure and stability of folded states of proteins, primary amino acid sequences determine all of the features of their conformational landscapes. Characterizing how sequence modulates the population of protein excited states or folding pathways requires atomic level detailed structural and energetic information. Such insight is essential for improving protein design strategies, as well as for interpreting protein evolution. Here, high pressure NMR and molecular dynamics simulations were combined to probe the conformational landscape of a small model protein, the tryptophan cage variant, Tc5b...
January 20, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28106985/transparent-window-vibrational-probes-for-the-characterization-of-proteins-with-high-structural-and-temporal-resolution
#11
Ramkrishna Adhikary, Jörg Zimmermann, Floyd E Romesberg
Vibrational spectroscopy provides a direct route to the physicochemical characterization of molecules. While both IR and Raman spectroscopy have been used for decades to provide detailed characterizations of small molecules, similar studies with proteins are largely precluded due to spectral congestion. However, the vibrational spectra of proteins do include a "transparent window", between ∼1800 and ∼2500 cm(-1), and progress is now being made to develop site-specifically incorporated carbon-deuterium (C-D), cyano (CN), thiocyanate (SCN), and azide (N3) "transparent window vibrational probes" that absorb within this window and report on their environment to facilitate the characterization of proteins with small molecule-like detail...
January 20, 2017: Chemical Reviews
https://www.readbyqxmd.com/read/28106933/carbatriphyrin-3-1-1-displays-distinct-coordination-approach-of-biii-to-generate-organoborane-and-weak-c-h%C3%A2-b-interactions
#12
Alagar Srinivasan, B Adinarayana, Ajesh P Thomas, Prerna Yadav, Vanga Mukundam
The carbatriphyrin(3.1.1) is the structural isomer of biphenylcorrole and achieved by switching the bonding mode of biphenyl unit from 3,3' to 2,3' which turns the corrole into triphyrin analogue. The presence of m-arene unit in the framework restricts the overall conjugation, thus leads to non-aromatic macrocycle. The protonation experiments afford trifluoroacetate ion complex. The coordination chemistry reveals that the bottom approach of boron(III) ion forms weak C-H...B interactions, however top approach stabilizes the organoborane complex and the product distribution relies on the basicity of the proton scavengers...
January 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28106930/local-proton-source-in-the-electrocatalytic-co2-reduction-by-mn-bpy-r-co-3br-complexes
#13
Carlo Nervi, Federico Franco, Claudio Cometto, Luca Nencini, Claudia Barolo, Fabrizio Sordello, Claudio Minero, Jan Fiedler, Marc Robert, Roberto Gobetto
The electrochemical behavior of fac-[Mn(pdbpy)(CO)3Br] (pdbpy = 4-phenyl-6-(phenyl-2,6-diol)-2,2'-bipyridine), 1, in acetonitrile under Ar and its catalytic performances for CO2 reduction with added water, 2,2',2''-trifluoroethanol (TFE) and phenol are discussed in detail. Preparative-scale electrolysis experiments, carried out at -1.5 V vs. SCE in CO2-saturated acetonitrile solutions, reveal that the process selectivity is extremely sensitive to the acid strength, providing CO and formate in different faradaic yields...
January 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28106900/vesicle-formation-by-proton-transfer-driven-short-tailed-fatty-acids-of-c4-c8-chain-length-in-water
#14
Li-Chun Chen, Hong-Peng Wang, Yu-Hao Deng, Shao-Ping Deng
Ultrashort single-chain fatty acids self-assemble to form vesicles under certain proton-driven conditions. The protonation provides a larger charge area around the hydrophilic carbonyl headgroups, and proton shift as the key driving parameter was studied. The ultrashort fatty acids (C4-C8) formed stable unilamellar vesicles predominantly through out the whole range of tested pH levels (6.5-9.5). A proton-driven self-assembly process and effects on the phase transition were characterized by dynamic light scattering, transmission electron microscopy and cryo-transmission electron microscopy...
January 20, 2017: Soft Matter
https://www.readbyqxmd.com/read/28106855/pharmacomodulation-of-the-antimalarial-plasmodione-synthesis-of-biaryl-and-n-arylalkylamine-analogues-antimalarial-activities-and-physicochemical-properties
#15
Karène Urgin, Mouhamad Jida, Katharina Ehrhardt, Tobias Müller, Michael Lanzer, Louis Maes, Mourad Elhabiri, Elisabeth Davioud-Charvet
With the aim of increasing the structural diversity on the early antimalarial drug plasmodione, an efficient and versatile procedure to prepare a series of biaryl- and N-arylalkylamines as plasmodione analogues is described. Using the naturally occurring and commercially available menadione as starting material, a 2-step sequence using a Kochi-Anderson reaction and subsequent Pd-catalyzed Suzuki-Miyaura coupling was developed to prepare three representative biphenyl derivatives in good yields for antimalarial evaluation...
January 19, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28106743/design-synthesis-and-antifungal-activity-evaluation-of-new-thiazolin-4-ones-as-potential-lanosterol-14%C3%AE-demethylase-inhibitors
#16
Anca Stana, Dan C Vodnar, Radu Tamaian, Adrian Pîrnău, Laurian Vlase, Ioana Ionuț, Ovidiu Oniga, Brînduşa Tiperciuc
Twenty-three thiazolin-4-ones were synthesized starting from phenylthioamide or thiourea derivatives by condensation with α-monochloroacetic acid or ethyl α-bromoacetate, followed by substitution in position 5 with various arylidene moieties. All the synthesized compounds were physico-chemically characterized and the IR (infrared spectra), ¹H NMR (proton nuclear magnetic resonance), (13)C NMR (carbon nuclear magnetic resonance) and MS (mass spectrometry) data were consistent with the assigned structures...
January 17, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/28106383/synthesis-chemistry-and-electronic-structures-of-group-9-metallaboranes
#17
Rosmita Borthakur, Sourav Kar, Subrat Kumar Barik, Somnath Bhattacharya, Gargi Kundu, Babu Varghese, Sundargopal Ghosh
Dimetallaoctaborane(12) of Ru, Co, and Rh have been well-characterized by a range of spectroscopic techniques and X-ray diffraction studies. Thus, reinvestigation of the Ir-system became of interest. As a result, a slight modification in the reaction conditions enabled us to isolate the missing Ir analogue of octaborane(12), [(Cp*Ir)2B6H10], 1. Compound 1 adapts a geometry similar to that of its parent octaborane(12) and Ru, Co, and Rh analogues. In [M2B6H10+x](M = Ru, x = 2; M = Co and Rh, x = 0), there exist two M-H-B protons...
January 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28106371/enhancement-of-electrode-stability-using-platinum-cobalt-nanocrystals-on-a-novel-composite-sictic-support
#18
María Millán, Hector Zamora, Manuel Andrés Rodrigo, Justo Lobato
PtCo alloy catalysts for high temperature PEMFCs (Protonic Exchange Membrane Fuel Cells) were synthesized on a novel non-carbonaceous support (SiCTiC) using the impregnation method with NaBH4 as the reducing agent at different synthesis temperatures to evaluate the effect of this variable on their physicochemical and electrochemical properties. The catalysts were characterized by inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), transmission electron microscope-energy dispersive X-ray (TEM) and temperature programmed reduction (TPR)...
January 20, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28106370/redox-active-cation-intercalation-deintercalation-in-two-dimensional-layered-mno2-nanostructures-for-high-rate-electrochemical-energy-storage
#19
Pan Xiong, Renzhi Ma, Nobuyuki Sakai, Xueyin Bai, Shen Li, Takayoshi Sasaki
Two-dimensional (2D) layered materials with high intercalation pseudocapacitance have long been investigated for Li+-ion-based electrochemical energy storage. By contrast, the exploration of guest ions other than Li+ has been limited, although promising. The present study investigate the intercalation/deintercalation behaviors of various metal ions in 2D layered MnO2 with various interlayer distances, K-birnessite nanobelt (K-MnO2), its protonated form (H-MnO2), and a freeze-dried sample of exfoliated nanosheets...
January 20, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28106328/on-the-influence-of-the-protonation-states-of-active-site-residues-on-ache-reactivation-a-qm-mm-approach
#20
Thomas Driant, Florian Nachon, Cyril Ollivier, Pierre-Yves Renard, Etienne Derat
Acetylcholinesterase (AChE) is an enzyme of the serine hydrolase superfamily and a mediator of the signal transmission at cholinergic synapses catalysing acetylcholine cleavage into an acetate and a choline. This enzyme is vulnerable to covalent inhibition by organophosphate compounds (like VX). The covalent inhibition of AChE does not revert spontaneously and in order to restore catalytic activity known reactivator compounds have limited action. Simulations of VX-inhibited AChE reactivation by pralidoxime, a classical reactivator, were performed by QM/MM...
January 19, 2017: Chembiochem: a European Journal of Chemical Biology
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