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https://www.readbyqxmd.com/read/28212316/succinimide-formation-from-an-ngr-containing-cyclic-peptide-computational-evidence-for-catalytic-roles-of-phosphate-buffer-and-the-arginine-side-chain
#1
Ryota Kirikoshi, Noriyoshi Manabe, Ohgi Takahashi
The Asn-Gly-Arg (NGR) motif and its deamidation product isoAsp-Gly-Arg (isoDGR) have recently attracted considerable attention as tumor-targeting ligands. Because an NGR-containing peptide and the corresponding isoDGR-containing peptide target different receptors, the spontaneous NGR deamidation can be used in dual targeting strategies. It is well known that the Asn deamidation proceeds via a succinimide derivative. In the present study, we computationally investigated the mechanism of succinimide formation from a cyclic peptide, c[CH₂CO-NGRC]-NH₂, which has recently been shown to undergo rapid deamidation in a phosphate buffer...
February 16, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/28212052/proton-density-fat-fraction-measurements-at-1-5-and-3-t-hepatic-mr-imaging-same-day-agreement-among-readers-and-across-two-imager-manufacturers
#2
Suraj D Serai, Jonathan R Dillman, Andrew T Trout
Purpose To determine the agreement of proton density fat fraction (PDFF) measurements obtained with hepatic magnetic resonance (MR) imaging among readers, imager manufacturers, and field strengths. Materials and Methods This HIPAA-compliant study was approved by the institutional review board. After providing informed consent, 24 adult volunteers underwent imaging with one 1.5-T MR unit (Ingenia; Philips Healthcare, Best, the Netherlands) and two different 3.0-T units (750 W [GE Healthcare, Waukesha, Wis] and Ingenia) on the same day to estimate hepatic PDFF...
February 24, 2017: Radiology
https://www.readbyqxmd.com/read/28212031/bond-activation-and-hydrogen-evolution-from-water-through-reactions-with-m3s4-m-mo-w-and-w3s3-anionic-clusters
#3
Corrine A Kumar, Arjun Saha, Krishnan Raghavachari
Transition metal sulfides (TMS) are being investigated with increased frequency because of their ability to efficiently catalyze the hydrogen evolution reaction. We have studied the trimetallic TMS cluster ions, Mo3S4(-), W3S4(-), and W3S3(-), and probed their efficiency for bond activation and hydrogen evolution from water. These clusters have geometries that are related to the edge sites on bulk MoS2 surfaces that are known to play a role in hydrogen evolution. Using density functional theory, the electronic structures of these clusters and their chemical reactivity with water have been investigated...
February 17, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28211935/the-vertical-location-of-%C3%AE-tocopherol-in-phosphatidylcholine-membranes-is-not-altered-as-a-function-of-the-degree-of-unsaturation-of-the-fatty-acyl-chains
#4
Alessio Ausili, Ana M de Godos, Alejandro Torrecillas, Francisco J Aranda, Senena Corbalán-García, Juan C Gómez-Fernández
α-Tocopherol is a natural preservative that prevents free radical chain oxidations in biomembranes. We have studied the location of α-tocopherol in model membranes formed by different unsaturated phosphatidylcholines, namely 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC), 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC) and 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PDPC). Small angle X-ray diffraction revealed that α-tocopherol was well mixed with all the phospholipids...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28205347/robust-universal-nonrigid-motion-correction-framework-for-first-pass-cardiac-mr-perfusion-imaging
#5
Mitchel Benovoy, Matthew Jacobs, Farida Cheriet, Nagib Dahdah, Andrew E Arai, Li-Yueh Hsu
PURPOSE: To present and assess an automatic nonrigid image registration framework that compensates motion in cardiac magnetic resonance imaging (MRI) perfusion series and auxiliary images acquired under a wide range of conditions to facilitate myocardial perfusion quantification. MATERIALS AND METHODS: Our framework combines discrete feature matching for large displacement estimation with a dense variational optical flow formulation in a multithreaded architecture...
February 15, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28202273/lithium-recovery-with-liti2o4-ion-sieves
#6
C-W Chen, P-A Chen, C-J Wei, H-L Huang, C-J Jou, Y-L Wei, H Paul Wang
A feasibility study for the recovery of lithium from salt water with the protonated lithium titanium oxide ion-sieves was carried out in this work. Lithium ions (Li(+)) in LiTi2O4 having a similar ion density with H(+) allow repeated exchanges and regeneration with high selectivity. By Li(7) magic angle spinning solid-state magnetic resonance, it is apparent that chemical structure of lithium in the ion-sieves is not perturbed during the repeated Li(+)/H(+) exchange processes. As the dissolution of titanium is negligible (<0...
February 12, 2017: Marine Pollution Bulletin
https://www.readbyqxmd.com/read/28197928/enhanced-reactivity-in-nucleophilic-acyl-substitution-ion-ion-reactions-using-triazole-ester-reagents
#7
Jiexun Bu, Zhou Peng, Feifei Zhao, Scott A McLuckey
The acyl substitution reactions between 1-hydroxy-7-aza-benzotriazole (HOAt)/1-hydroxy-benzotriazole (HOBt) ester reagents and nucleophilic side chains on peptides have been demonstrated in the gas phase via ion/ion reactions. The HOAt/HOBt ester reagents were synthesized in solution and ionized via negative nano-electrospray ionization. The anionic reagents were then reacted with doubly protonated model peptides containing amines, guanidines, and imidazoles in the gas phase. The complexes formed in the reaction cell were further probed with ion trap collision induced dissociation (CID) yielding either a covalently modified analyte ion or a proton transfer product ion...
February 14, 2017: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/28197402/suicide-inhibition-of-cytochrome-p450-enzymes-by-cyclopropylamines-via-a-ring-opening-mechanism-proton-coupled-electron-transfer-makes-a-difference
#8
Xiaoqian Zhang, Xiao-Xi Li, Yufang Liu, Yong Wang
N-benzyl-N-cyclopropylamine (BCA) has been attracting great interests for decades for its partial suicide inactivation role to cytochrome P450 (P450) via a ring-opening mechanism besides acting as a role of normal substrates. Understanding the mechanism of such partial inactivation is vital to the clinical drug design. Thus, density functional theoretical (DFT) calculations were carried out on such P450-catalyzed reactions, not only on the metabolic pathway, but on the ring-opening inactivation one. Our theoretical results demonstrated that, in the metabolic pathway, besides the normal carbinolamine, an unexpected enamine was formed via the dual hydrogen abstraction (DHA) process, in which the competition between rotation of the H-abstracted substrate radical and the rotation of hydroxyl group of the protonated Cpd II moiety plays a significant role in product branch; In the inactivation pathway, the well-noted single electron transfer (SET) mechanism-involved process was invalidated for its high energy barrier, a proton-coupled electron transfer [PCET(ET)] mechanism plays a role...
2017: Frontiers in Chemistry
https://www.readbyqxmd.com/read/28196133/b1-insensitive-t2-mapping-of-healthy-thigh-muscles-using-a-t2-prepared-3d-tse-sequence
#9
Elisabeth Klupp, Dominik Weidlich, Sarah Schlaeger, Thomas Baum, Barbara Cervantes, Marcus Deschauer, Hendrik Kooijman, Ernst J Rummeny, Claus Zimmer, Jan S Kirschke, Dimitrios C Karampinos
PURPOSE: To propose a T2-prepared 3D turbo spin echo (T2prep 3D TSE) sequence for B1-insensitive skeletal muscle T2 mapping and compare its performance with 2D and 3D multi-echo spin echo (MESE) for T2 mapping in thigh muscles of healthy subjects. METHODS: The performance of 2D MESE, 3D MESE and the proposed T2prep 3D TSE in the presence of transmit B1 and B0 inhomogeneities was first simulated. The thigh muscles of ten young and healthy subjects were then scanned on a 3 T system and T2 mapping was performed using the three sequences...
2017: PloS One
https://www.readbyqxmd.com/read/28195725/theoretical-insight-into-the-conversion-mechanism-of-glucose-to-fructose-catalyzed-by-crcl2-in-imidazolium-chlorine-ionic-liquids
#10
Yaru Jing, Jun Gao, Chengbu Liu, Dongju Zhang
To better understand the efficient transformation of glucose to fructose catalyzed by chromium chlorides in imidazolium-based ionic liquids (ILs), density functional theory calculations have been carried out on a model system which describes the catalytic reaction by CrCl2 in 1,3-dimethylimidazolium chlorine (MMImCl) ionic liquid (IL). The reaction is shown to involve three fundamental processes: ring opening, 1,2-H migration, and ring closure. The reaction is calculated to exergonic by 3.8 kcal/mol with an overall barrier of 37...
February 14, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28195715/interfacial-interaction-of-titania-nanoparticles-and-ligated-uranyl-species-a-relativistic-dft-investigation
#11
Hong-Bo Zhao, Ming Zheng, Georg Schreckenbach, Qing-Jiang Pan
To understand interfacial behavior of actinides adsorbed onto mineral surfaces and unravel their structure-property relationship, the structures, electronic properties, and energetics of various ligated uranyl species adsorbed onto TiO2 surface nanoparticle clusters (SNCs) were examined using relativistic density functional theory. Rutile (110) and anatase (101) titania surfaces, experimentally known to be stable, were fully optimized. For the former, models studied include clean and water-free Ti27O64H20 (dry), partially hydrated (Ti27O64H20)(H2O)8 (sol) and proton-saturated [(Ti27O64H20)(H2O)8(H)2](2+) (sat), while defect-free and defected anatase SNCs involving more than 38 TiO2 units were considered...
February 14, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28195670/a-bunch-like-tertiary-amine-grafted-polysulfone-membrane-for-vrfbs-with-simultaneously-high-proton-conductivity-and-low-vanadium-ion-permeability
#12
Qinglong Tan, Shanfu Lu, Jiangju Si, Haining Wang, Chunxiao Wu, Xianfeng Li, Yan Xiang
Novel polysulfone membranes with bunch-like tertiary amine groups are synthesized with high ion selectivity and outstanding chemical stability for vanadium redox flow batteries (VRFBs). The bunch-like tertiary amine groups simultaneously act as an ionic conductor for proton hopping and vanadium ion transport obstacles. The performance of the membrane is tuned via controlling the grafting degree of the chloromethylated polysulfone. The results show that membranes show increasing proton over vanadium ion (σ/p) selectivity with increasing functional tertiary groups...
February 13, 2017: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/28193068/high-confidence-sequencing-of-phosphopeptides-by-electron-transfer-dissociation-mass-spectrometry-using-dinuclear-zinc-ii-complex
#13
Daiki Asakawa, Issey Osaka
Phosphorylation is the most abundant protein modification, and tandem mass spectrometry (MS(2)) with electron transfer dissociation (ETD) has proven to be a promising method for phosphoproteomic applications owing to its ability to determine phosphorylation sites on proteins. However, low precursor charge states hinder the ability to obtain useful information through peptide sequencing by ETD, and the presence of acidic phosphate groups contributes to a low charge state of peptide ions. In the present report, we used a dinuclear zinc complex, (Zn2L)(3+) (L = alkoxide form of 1,3-bis[bis(pyridin-2-ylmethyl)amino]propan-2-ol) for electrospray ionization (ESI), followed by ETD-MS(2) analysis...
December 20, 2016: Analytical Chemistry
https://www.readbyqxmd.com/read/28192921/topotactic-conversion-of-%C3%AE-fe2o3-nanowires-into-fep-as-a-superior-fluorosensor-for-nucleic-acid-detection-insights-from-experiment-and-theory
#14
Li Yang, Danni Liu, Shuai Hao, Fengli Qu, Ruixiang Ge, Yongjun Ma, Gu Du, Abdullah M Asiri, Liang Chen, Xuping Sun
Nanostructures possess distinct quenching ability toward fluorophores with different emission frequencies and have been intensively used as nanoquenchers for homogeneous nucleic acid detection. Complete understanding of such a sensing system will provide significant guidance for the design of superior sensing materials, which is still lacking. In this Letter, we demonstrate the development of FeP nanowires as a nanoquencher for high-performance fluorescent nucleic acid detection with much superior performance to α-Fe2O3 counterparts...
February 1, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28190853/high-snr-acquisitions-improve-the-repeatability-of-liver-fat-quantification-using-confounder-corrected-chemical-shift-encoded-mr-imaging
#15
Utaroh Motosugi, Diego Hernando, Curtis Wiens, Peter Bannas, Scott B Reeder
PURPOSE: To determine whether high signal-to-noise ratio (SNR) acquisitions improve the repeatability of liver proton density fat fraction (PDFF) measurements using confounder-corrected chemical shift-encoded magnetic resonance (MR) imaging (CSE-MRI). MATERIALS AND METHODS: Eleven fat-water phantoms were scanned with 8 different protocols with varying SNR. After repositioning the phantoms, the same scans were repeated to evaluate the test-retest repeatability. Next, an in vivo study was performed with 20 volunteers and 28 patients scheduled for liver magnetic resonance imaging (MRI)...
February 13, 2017: Magnetic Resonance in Medical Sciences: MRMS
https://www.readbyqxmd.com/read/28186779/gas-phase-ion-molecule-reactions-of-copper-hydride-anions-cuh2-and-cu2h3
#16
Athanasios Zavras, Hossein Ghari, Alireza Ariafard, Allan J Canty, Richard A J O'Hair
Gas-phase reactivity of the copper hydride anions [CuH2](-) and [Cu2H3](-) toward a range of neutral reagents has been examined via multistage mass spectrometry experiments in a linear ion trap mass spectrometer in conjunction with isotope labeling studies and Density Functional Theory (DFT) calculations. [CuH2](-) is more reactive than [Cu2H3](-), consistent with DFT calculations, which show it has a higher energy HOMO. Experimentally, [CuH2](-) was found to react with CS2 via hydride transfer to give thioformate (HCS2(-)) in competition with the formation of the organometallic [CuCS2](-) ion via liberation of hydrogen; CO2 via insertion to produce [HCuO2CH](-); methyl iodide and allyl iodide to give I(-) and [CuHI](-); and 2,2,2-trifluoroethanol and 1-butanethiol via protonation to give hydrogen and the product anions [CuH(OCH2CF3)](-) and [CuH(SBu)](-)...
February 10, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28182581/application-of-single-and-dual-energy-ct-brain-tissue-segmentation-to-pet-monitoring-of-proton-therapy
#17
Bianca Berndt, Guillaume Landry, Florian Schwarz, Thomas Tessonnier, Florian Kamp, Georgios Dedes, Christian Thieke, Matthias Wuerl, Christopher Kurz, Ute Ganswindt, Frank Verhaegen, Juergen Debus, Claus Belka, Wieland Sommer, Maximilian Reiser, Julia Bauer, Katia Parodi
The purpose of this work was to evaluate the ability of single and dual energy computed tomography (SECT, DECT) to estimate tissue composition and density for usage in Monte Carlo (MC) simulations of irradiation induced β<sup>+</sup> activity distributions. This was done to assess the impact on positron emission tomography (PET) range verification in proton therapy. A DECT-based brain tissue segmentation method was developed for white matter (WM), grey matter (GM) and cerebrospinal fluid (CSF)...
February 9, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28182418/translation-of-ligand-centered-hydrogen-evolution-reaction-activity-and-mechanism-of-a-rhenium-thiolate-from-solution-to-modified-electrodes-a-combined-experimental-and-density-functional-theory-study
#18
Wuyu Zhang, Andrew Z Haddad, Brady D Garabato, Pawel M Kozlowski, Robert M Buchanan, Craig A Grapperhaus
The homogeneous, nonaqueous catalytic activity of the rhenium-thiolate complex ReL3 (L = diphenylphosphinobenzenethiolate) for the hydrogen evolution reaction (HER) has been transferred from nonaqueous homogeneous to aqueous heterogeneous conditions by immobilization on a glassy carbon electrode surface. A series of modified electrodes based on ReL3 and its oxidized precursor [ReL3][PF6] were fabricated by drop-cast methods, yielding catalytically active species with HER overpotentials for a current density of 10 mA/cm(2), ranging from 357 to 919 mV...
February 9, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28182409/electrochemical-reduction-of-co2-at-functionalized-au-electrodes
#19
Yuxin Fang, John C Flake
Electrochemical reduction of CO2 provides an opportunity to store renewable energy as fuels with much greater energy densities than batteries. Product selectivity of the reduction reaction is known to be a function of the electrolyte and electrode; however, electrodes modified with functional ligands may offer new methods to control selectivity. Here, we report the electrochemical reduction of CO2 at functionalized Au surfaces with thiol-tethered ligands including: 2-mercaptopropionic acid, 4-pyridinylethanemercaptan and cysteamine...
February 9, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28179169/vertebral-bone-marrow-fat-bone-mineral-density-and-diabetes-the-osteoporotic-fractures-in-men-mros-study
#20
Yahtyng Sheu, Francesca Amati, Ann V Schwartz, Michelle E Danielson, Xiaojuan Li, Robert Boudreau, Jane A Cauley
Elevated vertebral bone marrow fat (BMF) among individuals with osteoporosis has been established in histomorphometric studies. Several studies have found a negative correlation between BMF and bone mineral density (BMD) at the spine in men and women across different age groups. Animal studies have also observed bone loss with increased BMF in mice with induced diabetes. Our study objective was to test the hypothesis that the association between BMF and BMD varies by diabetic status. We performed a cross-sectional study of 156 men aged 74-96years from the Osteoporotic Fractures in Men (MrOS) study at the Pittsburgh clinical site...
February 4, 2017: Bone
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