Magnetic Resonance Characterization Research Articles

5020Cardiac magnetic resonance characterization of maladaptive right ventricular hypertrophy in chronic pulmonary hypertension

5020Cardiac magnetic resonance characterization of maladaptive right ventricular hypertrophy in chronic pulmonary hypertension

Magic Echo for Nuclear Magnetic Resonance Characterization of Shales

Low-field nuclear magnetic resonance (NMR) has been widely applied in the oil industry as a noninvasive technique for rock analysis. There are many organic compounds, such as kerogen, in unconventional shale resources. However, it is difficult to evaluate solid organic matter in shales using common NMR techniques. Previous work has shown the use of a solid echo on shale samples provides more information than the standard T1–T2 method with spin echo. But for multiple homonuclear dipolar coupling present in shales, solid echo is less efficient. We propose a new multimagic-echo sequence for T1 and T1–T2 measurements. The magic echo and standard T1 and T2 measurement technologies are combined to provide a more complete evaluation of hydrogen-containing shale sample components. Compared with other measurements, magic-echo measurements provide more signal of organic matters in shale samples. The additional signal is contributed by homonuclear dipolar coupling in organic matter. The partial least-squares regress...

Magnetic Resonance and Ultrastructural Characterization of PEGylation-associated Vacuolation in Nonclinical Models

Conjugation with polyethylene glycol (PEG) is a strategy for improving the pharmaceutical properties of therapeutic proteins. In nonclinical studies of PEGylated compounds, microscopic tissue vacuolation is often observed, characterized ultrastructurally in this report by lysosomal distension. Although PEGylation-associated vacuolation appears to be of limited toxicologic concern when alternative therapies are limited, the risk-benefit considerations may be impacted by uncertainty about reversibility, lack of methods for monitoring PEG accumulation in vivo without biopsy, and the variability in tissues affected depending on species studied. We demonstrate the use of magnetic resonance spectroscopy (MRS) to measure PEG concentrations at multiple time points in vivo in the kidney with comparison to PEG concentrations ex vivo in body fluids and tissue extracts using nuclear magnetic resonance (NMR) spectroscopy. Furthermore, we demonstrate the use of these techniques to study distribution and elimination of PEG in a dog model of PEGylation-associated vacuolation. This report suggests that MRS could be further investigated as a feasible imaging-based method for monitoring PEG accumulation in a clinical setting in conjunction with NMR quantitation of PEG in plasma and urine.

Oxidative Desulfurization of Gas Oil Catalyzed by (TBA)4PW11Fe@PbO as an Efficient and Recoverable Heterogeneous Phase-Transfer Nanocatalyst

In this paper, a tetra(n-butyl)ammonium salt of ironIII-substituted phosphotungstate@lead oxide composite, (TBA)4PW11Fe@PbO, was successfully synthesized by the thermal decomposition method as a nanocatalyst for oxidative desulfurization (ODS) of gas oil. The incorporation of the materials was confirmed by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and 31P nuclear magnetic resonance (NMR) characterization methods. To evaluate the catalytic activity of (TBA)4PW11Fe@PbO, the ODS process was carried out using a CH3COOH/H2O2 oxidizing agent at 60 °C. From the attained results, the total sulfur and mercaptan content of real gas oil were reduced with 97% efficiency after 2 h. Furthermore, the various comparative experiments were performed to investigate the capability of (TBA)4PW11Fe@PbO in ODS of prepared model fuel. Results were indicated that the kinetics of sulfur oxida...

Chemokine CXCL7 Heterodimers: Structural Insights, CXCR2 Receptor Function, and Glycosaminoglycan Interactions.

Chemokines mediate diverse fundamental biological processes, including combating infection. Multiple chemokines are expressed at the site of infection; thus chemokine synergy by heterodimer formation may play a role in determining function. Chemokine function involves interactions with G-protein-coupled receptors and sulfated glycosaminoglycans (GAG). However, very little is known regarding heterodimer structural features and receptor and GAG interactions. Solution nuclear magnetic resonance (NMR) and molecular dynamics characterization of platelet-derived chemokine CXCL7 heterodimerization with chemokines CXCL1, CXCL4, and CXCL8 indicated that packing interactions promote CXCL7-CXCL1 and CXCL7-CXCL4 heterodimers, and electrostatic repulsive interactions disfavor the CXCL7-CXCL8 heterodimer. As characterizing the native heterodimer is challenging due to interference from monomers and homodimers, we engineered a “trapped” disulfide-linked CXCL7-CXCL1 heterodimer. NMR and modeling studies indicated that GAG heparin binding to the heterodimer is distinctly different from the CXCL7 monomer and that the GAG-bound heterodimer is unlikely to bind the receptor. Interestingly, the trapped heterodimer was highly active in a Ca2+ release assay. These data collectively suggest that GAG interactions play a prominent role in determining heterodimer function in vivo. Further, this study provides proof-of-concept that the disulfide trapping strategy can serve as a valuable tool for characterizing the structural and functional features of a chemokine heterodimer.

Visible to Infrared Diamond Photonics Enabled by Focused Femtosecond Laser Pulses

Diamond’s nitrogen-vacancy (NV) centers show great promise in sensing applications and quantum computing due to their long electron spin coherence time and because they can be found, manipulated, and read out optically. An important step forward for diamond photonics would be connecting multiple diamond NVs together using optical waveguides. However, the inertness of diamond is a significant hurdle for the fabrication of integrated optics similar to those that revolutionized silicon photonics. In this work, we show the fabrication of optical waveguides in diamond, enabled by focused femtosecond high repetition rate laser pulses. By optimizing the geometry of the waveguide, we obtain single mode waveguides from the visible to the infrared. Additionally, we show the laser writing of individual NV centers within the bulk of diamond. We use µ-Raman spectroscopy to gain better insight on the stress and the refractive index profile of the optical waveguides. Using optically detected magnetic resonance and confocal photoluminescence characterization, high quality NV properties are observed in waveguides formed in various grades of diamond, making them promising for applications such as magnetometry, quantum information systems, and evanescent field sensors.

Solid-State Nuclear Magnetic Resonance Structural Study of the Retinal-Binding Pocket in Sodium Ion Pump Rhodopsin.

The recently identified Krokinobacter rhodopsin 2 (KR2) functions as a light-driven sodium ion pump. The structure of the retinal-binding pocket of KR2 offers important insights into the mechanisms of KR2, which has motif of Asn112, Asp116, and Gln123 (NDQ) that is common among sodium ion pump rhodopsins but is unique among other microbial rhodopsins. Here we present solid-state nuclear magnetic resonance (NMR) characterization of retinal and functionally important residues in the vicinity of retinal in the ground state. We assigned chemical shifts of retinal C14 and C20 atoms, and Tyr218Cζ, Lys255Cε, and the protonated Schiff base of KR2 in lipid environments at acidic and neutral pH. 15N NMR signals of the protonated Schiff base showed a twist around the N-Cε bond under neutral conditions, compared with other microbial rhodopsins. These data indicated that the location of the counterion Asp116 is one helical pitch toward the cytoplasmic side. In acidic environments, the 15N Schiff base signal was shifted to a lower field, indicating that protonation of Asp116 induces reorientation during interactions between the Schiff base and Asp116. In addition, the Tyr218 residue in the vicinity of retinal formed a weak hydrogen bond with Asp251, a temporary Na+-binding site during the photocycle. These features may indicate unique mechanisms of sodium ion pumps.

The enhancement of electrochemical capacitance of biomass-carbon by pyrolysis of extracted nanofibers

Biomass-derived carbons have been extensively researched as electrode material for energy storage and conversion recently. However, most of the previous works convert crude biomass directly into carbon and the electrochemical capacitances for the resultant carbons are quite often underestimated as well as large variations in capacitances exist in literatures due to the complex nature of biomass, which practically hinder their applications. In this work, polysaccharide nanofibers were extracted from an inexpensive natural fungus using a hydrothermal method and were converted to porous carbon nanofibers (CNFs) by potassium hydroxide activation. The porous carbons were assembled into symmetric supercapacitors using both potassium hydroxide and an ionic liquid (IL) as electrolytes. Solid state nuclear magnetic resonance characterization showed that the micropores of the as-prepared carbons are accessible to the IL electrolyte when uncharged and thus high capacitance is expected. It is found in both electrolytes the electrochemical capacitances of CNFs are significantly higher than those of the porous carbon derived directly from the crude fungus. Furthermore, the CNFs delivered an extraordinary energy density of 92.3 Wh kg−1 in the IL electrolyte, making it a promising candidate for electrode materials for supercapacitors.

Coeffect of Na+ and Tetrapropylammonium (TPA+) in Alkali Treatment on the Fabrication of Mesoporous ZSM-5 Catalyst for Methanol-to-Hydrocarbons Reactions

This investigation focused on the study of formation mechanism for highly mesoporous ZSM-5 under the introduction of tetrapropylammonium hydroxide (TPAOH) during NaOH treatment. Determined based on N2 sorption, transmission electron spectroscopy, scanning electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma atomic emission spectroscopy, and 29Si magic-angle spinning nuclear magnetic resonance characterizations, increased mesoporosity, crystallinity, and surface integrity for the desilicated ZSM-5 were found after TPAOH introduction. This protective effect of tetrapropylammonium (TPA+) on desilication was reflected by increased surface SiO2/Al2O3 ratios with increased concentrations of TPA+. TPA+ was first confirmed to be mainly adsorbed on the Si(4Si, 0Al) sites to provide a protective effect. Na+ played an indispensable role in the induced desilication during alkali treatment. The co-effect of protective desilication from TPA+ and preferential desilicatio...

A definitive analytical spectroscopic study of Indian yellow, an ancient pigment used for dating purposes

The Raman spectrum of tartrazine has been mistakenly reported as being that of Indian yellow in the literature, which has serious consequences for the identification of this pigment in art works regarding their authentication. Unlike tartrazine, Indian yellow (a natural mixture of the magnesium and calcium salts of euxanthic acid) exhibits in its Raman spectrum a strong fluorescent background when visible excitation is used, however, excitation in the near infrared (1064nm) permitted the observation of the Raman bands from the raw pigment with the main features placed at 1346, 1368, 1425, 1441 and 1626cm−1. Indian yellow identification was assured by 1H and 13C Nuclear Magnetic Resonance characterization and the complete assignment of the proton and carbon resonances was accomplished using heteronuclear single quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC), nuclear overhauser effect spectroscopy (NOESY) and 1H–1H correlation spectroscopy (COSY). Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray fluorescence (XRF) analyzes were also conducted on a genuine sample of this historical pigment.

Magnetic resonance characterization of coupled gas and particle dynamics in a bubbling fluidized bed

The results of MRI measurements of void fraction and velocities of gas and solids in a bubbling fluidized bed are compared favorably with theory and CFD-DEM numerical simulations, and also find a wide distributions of velocities.

Usefulness of Combined Functional Assessment by Cardiac Magnetic Resonance and Tissue Characterization Versus Task Force Criteria for Diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy

Current task force criteria (TFC) of cardiac magnetic resonance (CMR) for the diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC/D) were generated by comparing probands (mean age of 44years) to healthy participants of the multi-ethnic study of atherosclerosis (mean age of 60years). These age differences may be a selection bias because right ventricular end-diastolic volume index decreases 4.6% per decade. Moreover, fat infiltration and late gadolinium enhancement were not included. We evaluated the diagnostic accuracy of TFC using the same methodology used by the task force but comparing probands and age- and gender-matched healthy controls and considering also other morphofunctional and tissue abnormalities detected by CMR. Forty-seven probands with previous diagnosis of ARVC/D (excluding probands if CMR was used for diagnosis) were compared with 216 age- and gender-matched healthy controls. TFC had optimal specificity (100%) but poor sensitivity (20% for major and 13% for minor criteria). The presence of any pre- and post-contrast signal abnormalities had 100% specificity and 81% sensitivity. The best diagnostic accuracy (98%) was achieved by the combined evaluation of any right ventricular wall motion abnormality (excluding hypokinesia) with any signal abnormality (including left ventricular fat infiltration and late gadolinium enhancement) yielding a 100% specificity and 96% sensitivity. Left ventricular was involved in 45% of the probands. Current TFC for CMR presented optimal specificity but poor sensitivity to identify patient with ARVC/D. Signal and wall motion parameters of CMR should be considered together to achieve the best diagnostic accuracy for the diagnosis of ARVC/D.

Rheological and nuclear magnetic resonance characterization of porcine plasma protein-stabilized gel-like emulsion affected by pH and heating

In the present work, gel-like characteristics of porcine plasma protein oil-in-water (O/W; 52/48, g/100 g) emulsion has been studied under the influence of pH and heating. Viscosity analyses indicated that emulsions exhibited shear-thinning behaviors. Viscosity at pH6.5 and pH7.0 was significant higher than that of pH5.0 (P < 0.05). After 48 h storage, emulsions showed higher stability than 91.07%. From pH 5.0 to 7.0, final storage modulus and final loss modulus showed increase trend; compared with latter, former had always higher value which means more elasticity characteristics. Increase of pH caused a significant hardness strengthened effect (P < 0.05). Within the tested range, water holding capacity ranged from 94.02% to 96.97% indicating good thermal stability. Nuclear magnetic resonance test showed that pH higher than 5.5 bring non-heating emulsion higher T22 fraction which means more non-mobility water (P < 0.05). Cooking exhibited significant positive effects on the non-mobility status of water proton on samples at pH 5.0 and 5.5.Overall, gel-like characteristics of porcine plasma protein emulsion can be modified by pH and heating. Taking into account all factors, plasma protein emulsion should be adjusted to pH higher than 5.5 for the structuring of gel-like characteristics.

Magnetic Resonance Characterization of Cardiac Adaptation and Myocardial Fibrosis in Pulmonary Hypertension Secondary to Systemic-To-Pulmonary Shunt.

Pulmonary hypertension (PH) and right ventricular (RV) dysfunction are strong predictors of morbidity and mortality among patients with congenital heart disease. Early detection of RV involvement may be useful in the management of these patients. We aimed to assess progressive cardiac adaptation and quantify myocardial extracellular volume in an experimental porcine model of PH because of aorto-pulmonary shunt using cardiac magnetic resonance (CMR). To characterize serial cardiac adaptation, 12 pigs (aorto-pulmonary shunt [n=6] or sham operation [n=6]) were evaluated monthly with right heart catheterization, CMR, and computed tomography during 4 months, followed by pathology analysis. Extracellular volume by CMR in different myocardial regions was studied in 20 animals (aorto-pulmonary shunt [n=10] or sham operation [n=10]) 3 months after the intervention. All shunted animals developed PH. CMR evidenced progressive RV hypertrophy and dysfunction secondary to increased afterload and left ventricular dilatation secondary to volume overload. Shunt flow by CMR strongly correlated with PH severity, left ventricular end-diastolic pressure, and left ventricular dilatation. T1-mapping sequences demonstrated increased extracellular volume at the RV insertion points, the interventricular septum, and the left ventricular lateral wall, reproducing the pattern of fibrosis found on pathology. Extracellular volume at the RV insertion points strongly correlated with pulmonary hemodynamics and RV dysfunction. Prolonged systemic-to-pulmonary shunting in growing piglets induces PH with biventricular remodeling and myocardial fibrosis that can be detected and monitored using CMR. These results may be useful for the diagnosis and management of congenital heart disease patients with pulmonary overcirculation.

Magnetic Resonance Characterization of One-Electron Oxidized Cyclic Dipeptides with Thioether Groups.

Photo-oxidation of seven cyclic dipeptides containing methionine, Met, and/or S-methylcysteine, Cys(Me) by electron transfer from the sulfur atom was studied in aqueous solution by time-resolved and field dependent CIDNP (chemically induced dynamic nuclear polarization). Hyperpolarized high resolution NMR spectral patterns of the starting peptides detected immediately after pulsed laser excitation show signals of all protons that are bound to carbons neighboring the sulfur atom, thus proving the involvement of sulfur-centered cation radicals. The magnetic field dependence of CIDNP shows a pronounced maximum that is determined by the g-factors and hyperfine coupling constants of the transient radical species. From simulation of the experimental data obtained for the magnetic field dependences of CIDNP, three types of radical structures were characterized: (1) a linear sulfur-centered cation radical of the methionine (Met) residue (g = 2.0107 ± 0.0010) for cyclo-(d-Met-l-Met) (trans-configuration), cyclo-(d-Met-l-Cys(Me)) (trans-configuration), and cyclo-(Gly-Met); (2) a cyclic radical (S∴O)(+) (g = 2.0088 ± 0.0010) with a two-center three-electron bond (2c-3e) structure between the sulfur atom of the Cys(Me) residue and the oxygen atom of cyclo-(d-Met-l-Cys(Me)) and cyclo-(Gly-Cys(Me)); (3) a cyclic radical (S∴S)(+) (g = 2.013 ± 0.0020) with a two-center three-electron bond structure between the two sulfur atoms of the peptides cyclo-(l-Met-l-Met), cyclo-(l-Met-l-Cys(Me)), and cyclo-(l-Cys(Me)-l-Cys(Me)). In contrast, no indication of any type of cyclic radicals with a two-center three-electron bond between sulfur and nitrogen atoms was found. In addition, the hyperfine coupling constants (HFCCs) were determined.

A Mechanism Study on Hydrothermal Carbonization of Waste Textile

In this work, waste textile (WT) was employed as one representative pseudo-component of municipal solid waste (MSW) to investigate the mechanisms during hydrothermal carbonization (HTC) process. The experiments were examined at 230 and 280 °C with the residence time from 30 min to 90 min. The chemical component analysis showed that a significant fraction of fixed carbon was retained within the hydrochar, while ∼98% volatile matter was detected in the soluble fraction. Our results clearly demonstrate that decarboxylation was the most important defunctionalization process, whereas dehydration turned out to be less important. The combustibility index (S) and the combustion stability index (Rw) of the hydrochar were both greater than those of WT, suggesting hydrochar was superior in combustion performance. Fourier transform infrared (FTIR) analysis and solid-state 13C nuclear magnetic resonance (NMR) characterization displayed that large amount of aliphatic compounds decomposed, while enhancements of aromatic...

HyperCEST detection of cucurbit[6]uril in whole blood using an ultrashort saturation Pre-pulse train.

Xenon based biosensors have the potential to detect and localize biomarkers associated with a wide variety of diseases. The development and nuclear magnetic resonance (NMR) characterization of cage molecules which encapsulate hyperpolarized xenon is imperative for the development of these xenon biosensors. We acquired (129) Xe NMR spectra, and magnetic resonance images and a HyperCEST saturation map of cucurbit[6]uril (CB6) in whole bovine blood. We observed a mean HyperCEST depletion of 84% (n = 5) at a concentration of 5 mM and 74% at 2.5 mM. Additionally, we collected these data using a pulsed HyperCEST saturation pre-pulse train with a SAR of 0.025 W/kg which will minimize any potential RF heating in animal or human tissue. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis and Reaction Mechanism of Novel Fluorinated Carbon Fiber as a High-Voltage Cathode Material for Rechargeable Na Batteries

While a rechargeable battery based on Na/CFx has been proposed, its reversible mechanism has remained unclear. Here, a new fluorinated carbon fiber material with the formula CF0.75 is used as a cathode material for rechargeable sodium batteries, delivering an initial discharge capacity of 705 mA·h g–1 with a high discharge plateau of 2.75 V and a reversible high discharge capacity of 350 mA·h g–1 at 20 mA g–1. The first discharge plateau of 2.75 V is the highest value reported in this family of materials so far, even slightly higher than that of commercial fluorinated graphite tested in a lithium battery (2.7 V). The origins of the observed high voltage of the material are explored by a combination of theoretical calculations and galvanostatic intermittent titration technique data and determined to be related to the disordered structure of the carbon fiber. Soft X-ray absorption spectroscopy and 19F magic angle spinning nuclear magnetic resonance characterization results disclose a full view of the conver...

ZIF-8 Cooperating in TiN/Ti/Si Nanorods as Efficient Anodes in Micro-Lithium-Ion-Batteries.

Zeolite imidazolate framework-8 (ZIF-8) nanoparticles embedded in TiN/Ti/Si nanorod (NR) arrays without pyrolysis have shown increased energy storage capacity as anodes for lithium ion batteries (LIBs). A high capacity of 1650 μAh cm(-2) has been achieved in this ZIF-8 composited multilayered electrode, which is ∼100 times higher than the plain electrodes made of only silicon NR. According to the electrochemical impedance spectroscopy (EIS) and (1)H nuclear magnetic resonance (NMR) characterizations, the improved diffusion of lithium ions in ZIF-8 and boosted electron/Li(+) transfer by the ZIF-8/TiN/Ti multilayer coating are proposed to be responsible for the enhanced energy storage ability. The first-principles calculations further indicate the favorable accessibility of lithium with appropriate size to diffuse in the open pores of ZIF-8. This work broadens the application of ZIF-8 to silicon-based LIBs electrodes without the pyrolysis and provides design guidelines for other metal-organic frameworks/Si composite electrodes.

Cardiovascular magnetic resonance characterisation of pericardial and myocardial involvement in patients with tuberculous pericardial constriction with and without HIV co-infection

Cardiovascular magnetic resonance characterisation of pericardial and myocardial involvement in patients with tuberculous pericardial constriction with and without HIV co-infection