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https://www.readbyqxmd.com/read/28731616/inversion-recovery-ultrashort-echo-time-imaging-of-ultrashort-t2-tissue-components-in-ovine-brain-at-3%C3%A2-t-a-sequential-d2-o-exchange-study
#1
Shu-Juan Fan, Yajun Ma, Eric Y Chang, Graeme M Bydder, Jiang Du
Inversion recovery ultrashort echo time (IR-UTE) imaging holds the potential to directly characterize MR signals from ultrashort T2 tissue components (STCs), such as collagen in cartilage and myelin in brain. The application of IR-UTE for myelin imaging has been challenging because of the high water content in brain and the possibility that the ultrashort T2 * signals are contaminated by water protons, including those associated with myelin sheaths. This study investigated such a possibility in an ovine brain D2 O exchange model and explored the potential of IR-UTE imaging for the quantification of ultrashort T2 * signals in both white and gray matter at 3 T...
July 21, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28726909/lysine-based-amino-functionalized-lipids-for-gene-transfection-the-protonation-state-in-monolayers-at-the-air-liquid-interface
#2
Stephanie Tassler, Christian Wölk, Christopher Janich, Bodo Dobner, Gerald Brezesinski
Cationic lipids are considered as non-viral carriers for genetic material used in gene therapy. They have no carcinogenic potential and cause low immune response compared to existing viral systems. The protonation degree of these cationic lipids is a crucial parameter for the binding behavior of polynucleotides (e.g., DNA). Newly synthesized peptide-mimic lysine-based amino-functionalized lipids have been investigated in 2D models as monolayers at the air-liquid interface. Standard surface pressure - area isotherms have been measured to prove the layer stability...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28724285/elucidating-potential-energy-surfaces-for-singlet-o2-reactions-with-protonated-deprotonated-and-di-deprotonated-cystine-using-a-combination-of-approximately-spin-projected-density-functional-theory-and-guided-ion-beam-mass-spectrometry
#3
Wenchao Lu, I-Hsien Midas Tsai, Yan Sun, Wenjing Zhou, Jianbo Liu
The reactivity of cystine towards electronically excited singlet O2 (a(1)Δg) has been long debated, despite the fact that most organic disulfides are susceptible to oxidation by singlet O2. We report a combined experimental and computational study on reactions of singlet O2 with gas-phase cystine at different ionization and hydration states, aimed to determine reaction outcomes, mechanisms and potential energy surfaces. Ion-molecule collisions of protonated and di-deprotonated cystine ions with (1)O2, in both the absence and the presence of a water ligand, were measured over a center-of-mass collision energy (Ecol) range from 0...
July 20, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28720222/molecular-insight-into-protein-binding-orientations-and-interaction-modes-on-hydrophobic-charge-induction-resin
#4
Hong-Fei Tong, Carlo Cavallotti, Shan-Jing Yao, Dong-Qiang Lin
Hydrophobic charge-induction chromatography (HCIC) with 4-mercaptoethyl-pyridine (MEP) as the functional ligand has been developed as a new technology for antibody purification. In the present work, molecular simulation methods were developed to investigate the interactions between the Fc fragment of IgG and a MEP ligand net. The MM/PBSA method was used to evaluate the binding energy for the MEP ligand net at different densities. It was found that ligand density had significant influence on the binding of Fc...
June 30, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28719208/quantification-of-hydrogen-bond-strength-based-on-interaction-coordinates-a-new-approach
#5
Sarvesh Kumar Kumar Pandey, Dhivya Manogaran, Sadasivam Manogaran, Henry F Schaefer
A new approach to quantify hydrogen bond strengths based on interaction coordinates (HBSBIC) is proposed and is very promising. In this research, it is assumed that the projected force field of the fictitious three atoms fragment (DHA) where D is the proton donor and A is the proton acceptor from the full molecular force field of the H-bonded complex characterizes the hydrogen bond. The "interaction coordinate (IC)" derived from the internal compliance matrix elements of this three atoms fragment measures how the DH covalent bond (its electron density) responds to constrained optimization when the HA hydrogen bond is stretched by a known amount (its electron density is perturbed by a specified amount)...
July 18, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28718966/dft-studies-on-the-mechanism-of-ag2-co3-catalyzed-hydroazidation-of-unactivated-terminal-alkynes-with-tms-n3-an-insight-into-the-silver-i-activation-mode
#6
Haiyan Yuan, Pin Xiao, Yiying Zheng, Jingping Zhang
Silver-mediated hydroazidation of unactivated alkynes has been developed as a new method for the synthesis of vinyl azides. Density functional theory calculations toward this reaction reveal that terminal alkynes with TMS-N3 participated hydroazidation proceed through HN3 formation, deprotonation and silver acetylides formation, nucleophilic addition, and protonation of terminal carbon by AgHCO3 . It is also found that water molecules and activation modes of Ag (I) have a significant influence on the title reaction mechanism...
July 18, 2017: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/28715888/h-%C3%AF-landscape-of-the-phenylacetylene-hcl-system-does-this-provide-the-gateway-to-the-markovnikov-addition
#7
Ginny Karir, Kodumudi S Viswanathan
Non covalently bonded complexes of phenylacetylene-HCl were studied using matrix isolation infrared spectroscopy and ab-initio calculations. Phenylacetylene (PhAc) is an interesting hydrogen bond precursor as it has multiple sites for weak interactions and it was therefore considered worthwhile to study PhAc-HCl landscape. The interactions in PhAc-HCl were identified using the shifts in the infrared frequencies of the precursor molecules, as a result of complex formation. Our experiments unambiguously revealed spectral signatures of two types of H-π complexes, in both of which HCl was the proton donor...
July 18, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28715689/structure-and-absolute-configuration-of-some-5-chloro-2-methoxy-n-phenylbenzamide-derivatives
#8
Alaaeldin M F Galal, Elsayed M Shalaby, Ahmed Abouelsayed, Medhat A Ibrahim, Emad Al-Ashkar, Atef G Hanna
The absolute configuration of 5-chloro-2-methoxy-N-phenylbenzamide single crystal [compound (1)] and the effect of introducing -[CH2]n-, n=1,2 group adjacent to the amide group [compounds (2) and (3)], were studied. Furthermore, the replacement of the methoxy group with a hydroxy group [compound (4)] was defined. Proton and carbon-13 NMR spectrometer were used to record the structural information of the prepared compounds. X-ray single crystal diffractometer were used to elucidate the 3D structural configurations...
July 4, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28714078/ternary-porous-cobalt-phosphoselenide-nanosheets-an-efficient-electrocatalyst-for-electrocatalytic-and-photoelectrochemical-water-splitting
#9
Yang Hou, Ming Qiu, Tao Zhang, Xiaodong Zhuang, Chang-Soo Kim, Chris Yuan, Xinliang Feng
Exploring efficient and earth-abundant electrocatalysts is of great importance for electrocatalytic and photoelectrochemical hydrogen production. This study demonstrates a novel ternary electrocatalyst of porous cobalt phosphoselenide nanosheets prepared by a combined hydrogenation and phosphation strategy. Benefiting from the enhanced electric conductivity and large surface area, the ternary nanosheets supported on electrochemically exfoliated graphene electrodes exhibit excellent catalytic activity and durability toward hydrogen evolution in alkali, achieving current densities of 10 and 20 mA cm(-2) at overpotentials of 150 and 180 mV, respectively, outperforming those reported for transition metal dichalcogenides and first-row transition metal pyrites catalysts...
July 17, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28711348/impact-of-molecular-flexibility-on-the-site-energy-shift-of-chlorophylls-in-photosystem-ii
#10
Daniele Narzi, Emanuele Coccia, Marco Manzoli, Leonardo Guidoni
Light harvesting from the Sun by antenna complexes surrounding the reaction center of Photosystem II represents the first step of the natural oxygenic photosynthesis performed by plants, algae and cyanobacteria. The excitation energy derived from the sunlight is absorbed by the chlorophylls of the antenna and subsequently conveyed to the reaction center of Photosystem II through resonant energy transfer mechanisms. In the special pair of chlorophylls of the reaction center the charge separation occurs, eventually leading to the oxidation of water molecules into protons, electrons and molecular oxygen...
July 8, 2017: Biophysical Chemistry
https://www.readbyqxmd.com/read/28710385/electron-transfer-chain-in-respiratory-complex-i
#11
Daniel R Martin, Dmitry V Matyushov
Complex I is a part of the respiration energy chain converting the redox energy into the cross-membrane proton gradient. The electron-transfer chain of iron-sulfur cofactors within the water-soluble peripheral part of the complex is responsible for the delivery of electrons to the proton pumping subunit. The protein is porous to water penetration and the hydration level of the cofactors changes when the electron is transferred along the chain. High reaction barriers and trapping of the electrons at the iron-sulfur cofactors are prevented by the combination of intense electrostatic noise produced by the protein-water interface with the high density of quantum states in the iron-sulfur clusters caused by spin interactions between paramagnetic iron atoms...
July 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28707382/neutron-crystallographic-studies-of-t4-lysozyme-at-cryogenic-temperature
#12
Le Li, Shantanu Shukla, Flora Meilleur, Robert F Standaert, Josh Pierce, Dean A A Myles, Matthew J Cuneo
Bacteriophage T4 lysozyme (T4L) has been used as a paradigm for seminal biophysical studies on protein structure, dynamics and stability. Approximately 700 mutants of this protein and their complexes have been characterized by X-ray crystallography; however, despite the high resolution diffraction limits attained in several studies, no hydrogen atoms were reported being visualized in the electron density maps. To address this, a 2.2 Å-resolution neutron data set was collected at 80 K from a crystal of perdeuterated T4L pseudo-wild type...
July 13, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28705058/standardized-approach-for-roi-based-measurements-of-proton-density-fat-fraction-and-r2-in-the-liver
#13
Camilo A Campo, Diego Hernando, Tilman Schubert, Candice A Bookwalter, Andrew J Van Pay, Scott B Reeder
OBJECTIVE: The purpose of this study was to evaluate the reproducibility (interreviewer agreement) and repeatability (intrareviewer agreement) of ROI sampling strategies to measure chemical shift-encoded (CSE) MRI-based liver proton density fat fraction (PDFF) and R2* (1 / T2*). A secondary purpose was to standardize ROI-based liver PDFF and R2* measurements by providing a compromise between measurement reproducibility and repeatability and time burden for image analysts. MATERIALS AND METHODS: CSE data from two cohorts were retrospectively analyzed...
July 13, 2017: AJR. American Journal of Roentgenology
https://www.readbyqxmd.com/read/28702799/greater-occipital-nerve-infiltration-under-mr-guidance-feasibility-study-and-preliminary-results
#14
Adrian Kastler, Romain Perolat, Bruno Kastler, Caroline Maindet-Dominici, Jan Fritz, Alim Louis Benabid, Stephan Chabardes, Alexandre Krainik
OBJECTIVE: To assess the feasibility of greater occipital nerve (GON) intermediate site infiltration with MRI guidance. METHODS: Eleven consecutive patients suffering from chronic refractory cranio-facial pain who underwent 16 GON infiltrations were included in this prospective study. All of the procedures were performed on an outpatient basis in the research facility of our institution, with a 1.5 T scanner. The fatty space between inferior obliquus and semispinalis muscles at C1-C2 level was defined as the target...
July 12, 2017: European Radiology
https://www.readbyqxmd.com/read/28700203/mechanisms-of-atmospherically-relevant-cluster-growth
#15
Bryan R Bzdek, Joseph W DePalma, Murray V Johnston
Atmospheric aerosols impact global climate either directly by scattering solar radiation or indirectly by serving as cloud condensation nuclei, which influence cloud albedo and precipitation patterns. Our scientific understanding of these impacts is poor relative to that of, for instance, greenhouse gases, in part because it is difficult to predict particle number concentrations. One important pathway by which particles are added to the atmosphere is new particle formation, where gas phase precursors form molecular clusters that subsequently grow to the climatically relevant size range (50-100 nm diameter)...
July 12, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28698004/the-effect-of-radiotherapy-on-fat-content-and-fatty-acids-in-myxoid-liposarcomas-quantified-by-mri
#16
Mikael Skorpil, Henric Rydén, Johan Wejde, Elisabet Lidbrink, Otte Brosjö, Johan Berglund
BACKGROUND: Myxoid liposarcomas are highly radiosensitive. Consequently radiotherapy is often used pre-operatively to reduce tumor volume and lessen the post-operative deficit. In soft-tissue sarcomas therapy response is mainly evaluated using magnetic resonance imaging (MRI) and the fundamental criterion for a positive response is decreased tumor size. In myxoid liposarcomas an increased fat content is also known to occur as a response to radiotherapy. OBJECTIVE: To highlight the difficulties of MRI for therapy response evaluation in irradiated myxoid liposarcomas, by using MRI Dixon techniques enabling objective quantification of proton density fat fraction (%) and the number of double bonds (ndb; unsaturation degree) of fatty acids...
July 8, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28696765/electric-dipole-polarizability-of-48-ca-and-implications-for-the-neutron-skin
#17
J Birkhan, M Miorelli, S Bacca, S Bassauer, C A Bertulani, G Hagen, H Matsubara, P von Neumann-Cosel, T Papenbrock, N Pietralla, V Yu Ponomarev, A Richter, A Schwenk, A Tamii
The electric dipole strength distribution in ^{48}Ca between 5 and 25 MeV has been determined at RCNP, Osaka from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the first extraction of the electric dipole polarizability α_{D}(^{48}Ca)=2.07(22)  fm^{3}. Remarkably, the dipole response of ^{48}Ca is found to be very similar to that of ^{40}Ca, consistent with a small neutron skin in ^{48}Ca. The experimental results are in good agreement with ab initio calculations based on chiral effective field theory interactions and with state-of-the-art density-functional calculations, implying a neutron skin in ^{48}Ca of 0...
June 23, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28693317/osmotic-heat-engine-using-thermally-responsive-ionic-liquids
#18
Yujiang Zhong, Xinbo Wang, Xiaoshuang Feng, Selvedin Telalovic, Yves Gnanou, Kuo-Wei Huang, Xiao Matthew Hu, Zhiping Lai
The osmotic heat engine (OHE) is a promising technology for converting low grade heat to electricity. Most of the existing studies have focused on thermolytic salt systems. Herein, for the first time, we proposed to use thermally responsive ionic liquids (TRIL) that have either an upper critical solution temperature (UCST) or lower critical solution temperature (LCST) type of phase behavior as novel thermolytic osmotic agents. Closed-loop TRIL-OHEs were designed based on these unique phase behaviors to convert low grade heat to work or electricity...
July 11, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28691816/mechanism-of-excited-state-intramolecular-proton-transfer-for-1-2-dihydroxyanthraquinone-effect-of-water-on-the-esipt
#19
Yajing Peng, Yuqing Ye, Xianming Xiu, Shuang Sun
Mechanisms of excited-state intramolecular proton transfer (ESIPT) of 1,2-dihydroxyanthraquinone (ALR) in ethanol solvent and binary solvent of water and ethanol are investigated using the density functional theory (DFT) and time-dependent density functional theory (TDDFT). The intramolecular hydrogen bond is found to be reinforced in the excited state based on the bond lengths, bond angles and infrared (IR) vibrational spectra of relevant group. The reinforcement of intramolecular hydrogen bond is attributed to the charge transfer in the excited state, which leads to the ESIPT to form a keto isomer...
July 10, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28691392/metal-free-nitrogen-doped-mesoporous-carbon-for-electroreduction-of-co2-to-ethanol
#20
Yanfang Song, Wei Chen, Chengcheng Zhao, Shenggang Li, Wei Wei, Yuhan Sun
CO2 electroreduction is a promising technique for satisfying both renewable energy storage and negative carbon cycle. However, it remains a challenge to convert CO2 to C2 products with high efficiency and selectivity. Herein, we report a nitrogen-doped ordered cylindrical mesoporous carbon as a robust metal-free catalyst for CO2 electroreduction, enabling the efficient production of ethanol with nearly 100% selectivity and high faradaic efficiency of 77% at -0.56 V versus the reversible hydrogen electrode. Our experiments and density functional theory calculations demonstrate that the synergetic effect of the nitrogen heteroatoms and the cylindrical channel configurations facilitates the dimerization of key CO* intermediates and the subsequent proton-electron transfers, resulting in superior electrocatalytic performance for synthesizing ethanol from CO2...
July 9, 2017: Angewandte Chemie
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