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https://www.readbyqxmd.com/read/28441539/a-quantum-chemical-insight-into-the-tunable-fluorescence-color-and-distinct-photoisomerization-mechanisms-between-a-novel-esipt-fluorophore-and-its-protonated-form
#1
Huijuan Yuan, Songyan Feng, Keke Wen, Qiuling Zhu, Beibei An, Xugeng Guo, Jinglai Zhang
Enol-keto proton tautomerization and cis-trans isomerization reactions of a novel excited-state intramolecular proton transfer (ESIPT) fluorophore of BTImP and its protonated form (BTImP(+)) were explored using density functional theory/time-dependent density functional theory (DFT/TD-DFT) computational methods with a B3LYP hybrid functional and the 6-31+G(d,p) basis set. In addition, the absorption and fluorescence spectra were calculated at the TD-B3LYP/6-31+G(d,p) level of theory. Our results reveal that both BTImP and BTImP(+) can undergo an ultrafast ESIPT reaction, giving rise to the single fluorescence emission with different fluorescence colors, which are nicely consistent with the experimental findings...
April 19, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28440570/mass-spectrometric-characterization-of-the-selective-androgen-receptor-modulator-sarm-yk-11-for-doping-control-purposes
#2
Mario Thevis, Thomas Piper, Josef Dib, Andreas Lagojda, Dirk Kuehne, Lars Packschies, Hans Geyer, Wilhelm Schaenzer
RATIONALE: Selective androgen receptor modulators (SARMs) represent an emerging class of therapeutics targeting inter alia conditions referred to as cachexia and sarcopenia. Due to their anabolic properties, the use of SARMs is prohibited in sports as regulated by the World Anti-Doping Agency (WADA), and doping control laboratories test for these anabolic agents in blood and urine. In order to accomplish and maintain comprehensive test methods, the characterization of new drug candidates is critical for efficient sports drug testing...
April 25, 2017: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/28435366/comparative-evaluation-of-antimicrobial-efficacy-of-triple-antibiotic-paste-calcium-hydroxide-and-a-proton-pump-inhibitor-against-resistant-root-canal-pathogens
#3
Shibha Mehta, Promila Verma, Aseem Prakash Tikku, Anil Chandra, Rhythm Bains, Gopa Banerjee
OBJECTIVE: The objective of this study is to compare the antimicrobial efficacy of triple antibiotic paste (TAP) and a proton pump inhibitor (PPI) (omeprazole) in combination with calcium hydroxide (CH) against Enterococcus faecalis and Candida albicans. MATERIALS AND METHODS: E. faecalis and C. albicans were subcultured and inoculated at 37° overnight and were treated with different dilutions of TAP, 25 μg/ml (Group 1), CH (Group 2, control), CH 16 mg/ml + omeprazole 2 mg/ml (Group 3a) (CH 16 mg/ml + omeprazole 4 mg)/ml (Group 3b) for 24, 48, and 72 h in sterile uncoated 96-well microtiter plates...
January 2017: European Journal of Dentistry
https://www.readbyqxmd.com/read/28433832/the-theoretical-study-of-excited-state-intramolecular-proton-transfer-of-2-5-bis-benzoxazol-2-yl-thiophene-3-4-diol
#4
Rui-Fang Lan, Yun-Fan Yang, Yan-Zhen Ma, Yong-Qing Li
The symmetrical structures 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol (BBTD) can take shape two intramolecular hydrogen bonds in chloroform. In order to research the molecular dynamic behavior of BBTD upon photo-induced process, we utilize density functional theory (DFT) and time-dependent density functional theory (TDDFT) to complete theoretical calculation. Through the comparison of bond length, bond angle, IR spectra, and frontier molecular orbitals between ground state (S0) and first excited state (S1), it clearly indicates that photoexcitation have slightly influence for intensity of hydrogen bond...
April 18, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28433034/direct-1-h-nmr-evidence-of-spin-rotation-coupling-as-a-source-of-para-%C3%A2-ortho-h2-conversion-in-diamagnetic-solvents
#5
Camilla Terenzi, Sabine Bouguet-Bonnet, Daniel Canet
At ambient temperature, conversion from 100% enriched para-hydrogen (p-H2; singlet state) to ortho-hydrogen (o-H2; triplet state) leads necessarily to the thermodynamic equilibrium proportions: 75% of o-H2 and 25% of p-H2. When p-H2 is dissolved in a diamagnetic organic solvent, conversion is very slow and can be considered as arising from nuclear spin relaxation phenomena. A first relaxation mechanism, specific to the singlet state and involving a combination of auto-correlation and cross correlation spectral densities, can be retained: randomly fluctuating magnetic fields due to inter-molecular dipolar interactions...
April 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28433032/ir-spectral-assignments-for-the-hydrated-excess-proton-in-liquid-water
#6
Rajib Biswas, William Carpenter, Joseph A Fournier, Gregory A Voth, Andrei Tokmakoff
The local environmental sensitivity of infrared (IR) spectroscopy to a hydrogen-bonding structure makes it a powerful tool for investigating the structure and dynamics of excess protons in water. Although of significant interest, the line broadening that results from the ultrafast evolution of different solvated proton-water structures makes the assignment of liquid-phase IR spectra a challenging task. In this work, we apply a normal mode analysis using density functional theory of thousands of proton-water clusters taken from reactive molecular dynamics trajectories of the latest generation multistate empirical valence bond proton model (MS-EVB 3...
April 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28432857/on-the-importance-of-intramolecular-hydrogen-bond-cooperativity-in-d-glucose-an-nmr-and-qtaim-approach
#7
John S Lomas, Laurent Joubert
The idea that hydrogen bond cooperativity is responsible for the structure and reactivity of carbohydrates is examined. Density functional theory and gauge-including atomic orbital calculations on the known conformers of the α and β anomers of D-glucopyranose in the gas phase are used to compute proton NMR chemical shifts and interatomic distances, which are taken as criteria for probing intramolecular interactions. Atom-atom interaction energies are calculated by the interacting quantum atoms approach in the framework of the quantum theory of atoms in molecules...
April 22, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28432504/3t-mri-of-the-knee-with-optimised-isotropic-3d-sequences-accurate-delineation-of-intra-articular-pathology-without-prolonged-acquisition-times
#8
Osamah M Abdulaal, Louise Rainford, Peter MacMahon, Eoin Kavanagh, Marie Galligan, James Cashman, Allison McGee
OBJECTIVES: To investigate optimised isotropic 3D turbo spin echo (TSE) and gradient echo (GRE)-based pulse sequences for visualisation of articular cartilage lesions within the knee joint. METHODS: Optimisation of experimental imaging sequences was completed using healthy volunteers (n=16) with a 3-Tesla (3T) MRI scanner. Imaging of patients with knee cartilage abnormalities (n=57) was then performed. Acquired sequences included 3D proton density-weighted (PDW) TSE (SPACE) with and without fat-suppression (FS), and T2*W GRE (TrueFISP) sequences, with acquisition times of 6:51, 6:32 and 5:35 min, respectively...
April 21, 2017: European Radiology
https://www.readbyqxmd.com/read/28432403/bone-marrow-fat-content-in-70-adolescent-girls-with-anorexia-nervosa-magnetic-resonance-imaging-and-magnetic-resonance-spectroscopy-assessment
#9
Kirsten Ecklund, Sridhar Vajapeyam, Robert V Mulkern, Henry A Feldman, Jennifer M O'Donnell, Amy D DiVasta, Catherine M Gordon
BACKGROUND: Adolescents and women with anorexia nervosa have increased bone marrow fat and decreased bone formation, at least in part due to hormonal changes leading to preferential stem cell differentiation to adipocytes over osteoblasts. OBJECTIVE: The purpose of this study was to evaluate marrow fat content and correlate with age and disease severity using knee MRI with T1 relaxometry (T1-R) and MR spectroscopy (MRS) in 70 adolescents with anorexia nervosa. MATERIALS AND METHODS: We enrolled 70 girls with anorexia nervosa who underwent 3-T knee MRI with coronal T1-W images, T1-R and single-voxel proton MRS at 30 and 60 ms TE...
April 22, 2017: Pediatric Radiology
https://www.readbyqxmd.com/read/28432188/magnetic-resonance-neurography-visualizes-abnormalities-in-sciatic-and-tibial-nerves-in-patients-with-type-1-diabetes-and-neuropathy
#10
Michael Vaeggemose, Mirko Pham, Steffen Ringgaard, Hatice Tankisi, Niels Ejskjaer, Sabine Heiland, Per L Poulsen, Henning Andersen
This study evaluates whether diffusion-tensor-imaging MR-Neurography (DTI-MRN), T2-relaxation-time and proton-spin-density can detect and grade neuropathic abnormalities in patients with type 1 diabetes.Forty-nine patients with type 1 diabetes (11 with severe polyneuropathy (sDPN), 13 with mild polyneuropathy (mDPN) and 25 without polyneuropathy (nDPN)) and 30 healthy controls (HC) were included. Clinical examinations, nerve-conduction-studies and vibratory-perception-thresholds determined the presence and severity of DPN...
April 21, 2017: Diabetes
https://www.readbyqxmd.com/read/28430191/activating-lattice-oxygen-redox-reactions-in-metal-oxides-to-catalyse-oxygen-evolution
#11
Alexis Grimaud, Oscar Diaz-Morales, Binghong Han, Wesley T Hong, Yueh-Lin Lee, Livia Giordano, Kelsey A Stoerzinger, Marc T M Koper, Yang Shao-Horn
Understanding how materials that catalyse the oxygen evolution reaction (OER) function is essential for the development of efficient energy-storage technologies. The traditional understanding of the OER mechanism on metal oxides involves four concerted proton-electron transfer steps on metal-ion centres at their surface and product oxygen molecules derived from water. Here, using in situ (18)O isotope labelling mass spectrometry, we provide direct experimental evidence that the O2 generated during the OER on some highly active oxides can come from lattice oxygen...
May 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28429940/density-functional-theory-and-car-parrinello-molecular-dynamics-study-of-the-hydrogen-producing-mechanism-of-the-co-dmgbf2-2-and-co-dmgh-2-cobaloxime-complexes-in-the-acetonitrile-water-solvent
#12
Jinfan Chen, Patrick H-L Sit
The catalytic hydrogen-producing processes of two prototypical cobaloxime catalysts Co(dmgBF2)2 (dmgBF2=difluoroboryl-dimethylglyoxime) and Co(dmgH)2 (dmgH=dimethylglyoxime), were studied by Density Functional Theory (DFT) and Car-Parrinello molecular dynamics (CPMD) simulations in the explicit acetonitrile-water solvent. Our study demonstrates the key role of water molecules as shuttles to deliver protons to the cobalt active centers of these catalysts. However, the transfer of protons to the cobalt centers also competes with the diffusion of the proton away from the complex via the hydrogen bond network of water...
April 21, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28428209/myelin-detection-using-rapid-quantitative-mr-imaging-correlated-to-macroscopically-registered-luxol-fast-blue-stained-brain-specimens
#13
J B M Warntjes, A Persson, J Berge, W Zech
BACKGROUND AND PURPOSE: Myelin detection is of great value in monitoring diseases such as multiple sclerosis and dementia. However, most MR imaging methods to measure myelin are challenging for routine clinical use. Recently, a novel method was published, in which the presence of myelin is inferred by using its effect on the intra- and extracellular water relaxation rates and proton density, observable by rapid quantitative MR imaging. The purpose of this work was to validate this method further on the brains of 12 fresh, intact cadavers...
April 20, 2017: AJNR. American Journal of Neuroradiology
https://www.readbyqxmd.com/read/28427014/chemical-and-biological-properties-of-a-supramolecular-complex-of-tuftsin-and-cucurbit-7-uril
#14
Ekaterina A Kovalenko, Ekaterina A Pashkina, Lyubov Y Kanazhevskaya, Alexey N Masliy, Vladimir A Kozlov
Cucurbit[7]uril (CB7) is an uncharged and water-soluble macrocyclic host. CB7 binds to doubly protonated tuftsin, which is the tetrapeptide Thr-Lys-Pro-Arg, with moderate affinity (Ka=2.1×10(3)M(-1)). In this study, the host-guest complexation was confirmed by fluorescence titration. This affinity would allow for easy release of the peptide under physiological conditions. According to density functional theory calculations, the structural binding motif involves hydrogen bonding. The most energetically stable form had the Arg side chain inside the CB7 cavity...
April 17, 2017: International Immunopharmacology
https://www.readbyqxmd.com/read/28426209/channel-assisted-proton-conduction-behavior-in-hydroxyl-rich-lanthanide-based-magnetic-metal-organic-frameworks
#15
Soumava Biswas, Jayita Chakraborty, Vijay Singh Parmar, Siba Prasad Bera, Nirmal Ganguli, Sanjit Konar
Two new lanthanide-based 3D metal-organic frameworks (MOFs), {[Ln(L)(Ox)(H2O)]n·xH2O} [Ln = Gd(3+) and x = 3 (1) and Dy(3+) and x = 1.5 (2); H2L = mucic acid; OxH2 = oxalic acid] showing interesting magnetic properties and channel-mediated proton conduction behavior, are presented here. Single-crystal X-ray structure analysis shows that, in complex 1, the overall structure originates from the mucate-bridged gadolinium-based rectangular metallocycles. The packing view reveals the presence the two types of hydrophilic 1D channels filled with lattice water molecules, which are strongly hydrogen-bonded with coordinated water along the a and b axes, whereas for complex 2, the 3D framework originates from a carboxylate-bridged dysprosium-based criss-cross-type secondary building block...
April 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28426058/radical-cations-of-phenyl-silatrane
#16
Vitalijs Romanovs, Valery Sidorkin, Elena Belogolova, Viatcheslav Jouikov
Electrochemical oxidation of phenylsilatrane (1) in CH3CN/0.1 M Bu4NPF6 has been studied by voltammetry, UV-Vis and EPR-coupled spectroelectrochemistry supported by DFT calculations. One-electron withdrawal from the HOMO of 1, formed with a predominant contribution of the atrane N atom to the 3c-4e system, results in a short lived radical cation, in which the atrane nitrogen atom is almost planar and carries most of the spin density showing strong coupling with the protons of the axially directed C-H bonds of the three adjacent α-methylene groups (g = 2...
April 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28426056/chemical-pathways-for-poly-anionic-isomerisation-in-the-metastable-anions-of-tetra-deprotonated-naphthalene-an-intra-molecular-inter-ring-proton-transfer
#17
Vikas, Poonam Sangwan, Ramanpreet Kaur
A surprising chemical pathway involving an intra-molecular proton-transfer between the two different aromatic rings of naphthalene is revealed while exploring the isomerisation in the metastable tetra-anionic species of tetra-deprotonated naphthalene. The pathways are explored through quantum-mechanical computations employing a global reaction route mapping (GRRM) strategy. Notably, several other pathways traced exhibit interesting aspects of poly-anionic isomerisation in the multiply-charged metastable molecular anions, which can provide valuable insights into the mechanisms of ring closure and expansion leading to species like azulenes, cyclodecapentaene, and phenylvinylacetylene...
April 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28425542/acceptor-doping-in-the-proton-conductor-srzro3
#18
Leigh Weston, A Janotti, X Y Cui, C Stampfl, C G Van de Walle
Perovskite zirconates such as SrZrO3 exhibit improved proton solubility and conductivity when doped with trivalent cations substituting at the Zr site. In this work, we present a detailed study of Sc and Y dopants in SrZrO3 based on first-principles, hybrid density-functional calculations. When substituting at the Zr site (ScZr, YZr), both dopants give rise to a single, deep acceptor level, where the neutral impurity forms a localized hole polaron state. The ε(0/-) charge transition levels are 0.60 eV and 0...
April 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28423280/does-nitrogen-lone-pair-lead-to-two-centered-three-electrons-2c-3e-interactions-in-pyridyl-radical-isomers
#19
Chitranjan Sah, Lilit Jacob, Mayank Saraswat, Sugumar Venkataramani
Each of the three isomeric pyridyl radicals (2-, 3- and 4-dehydropyridines) contains a lone pair and an unpaired electron. As a result, a potential two centered - three electron interaction between the radical electron and the lone pair through space (TS) and/or through bond (TB) can exist that may influence the stability of the radicals. Due to the change in geometrical positions relative to each other the strength of interaction can be varied. In this study, we investigated the structural and stability aspects of pyridyl radical isomers with a major emphasis on the interaction of nitrogen lone pair with the radical center...
April 19, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28419591/application-of-spin-echoes-in-the-regime-of-weak-dephasing-to-t1-mapping-of-the-lung
#20
Jakob Assländer, Steffen J Glaser, Jürgen Hennig
PURPOSE: This work presents an approach to mapping the entire lung's proton density and T1 within a single breath-hold and analyzes the apparent T1 when exciting with a spin echo generating pulse in comparison to a standard gradient echo acquisition. METHODS: An inversion-recovery SNAPSHOT-FLASH sequence with a stack-of-stars k-space readout with a golden angle increment was modified to use a spin echo generating radiofrequency-pulse for excitation. Data of five volunteers were acquired on a 3T scanner and image reconstruction was performed by an iterative algorithm adopted from MR-Fingerprinting...
April 17, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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