Magnetic Resonance Characterization Research Articles

Selective isolation of in vitro phase II conjugates using a lipophilic anionic exchange solid phase extraction method

Identification, characterization and structure elucidation of human metabolites of drug candidates is crucial for the pharmaceutical industry to assess their activity against the therapeutic target of interest and potential toxicological effects. It often requires in vitro synthesis of microgram quantities of metabolites of interest with enzymatic preparations, pre-concentration of the reaction mixture by solid phase extraction (SPE), metabolite isolation using HPLC systems coupled to fraction collectors prior to nuclear magnetic resonance characterization. The method reported herein is a rapid and simple technique using solely off-line mixed phase anionic exchange lipophilic SPE cartridges to selectively isolate glucuronide and sulfate metabolites from their parent compound. This approach capitalizes on the p Ka differences between the parent compound, devoided of acidic moieties, and the negatively charged glucuronide and/or sulfate metabolites. Once loaded on the SPE cartridge, the incubation mixture is washed successively with a basic aqueous solution, methanol to elute the non-anionic parent compounds, and then with an acidic methanolic solution to protonate and recover the phase II conjugates. Over 100 μg (>95% purity) of 17α-ethynylestradiol-3-glucuronide and 6-gingerol-4′-glucuronide were successfully isolated using this technique, as well as glucuronide and a sulfate conjugates of 1-{4′-[(1 R)-2,2-difluoro-1-hydroxyethyl]biphenyl-4-yl}cyclopropanecarboxamide (DHBC) synthesized in-house. Their structures were confirmed by Ultra Performance Liquid Chromatography coupled to Quadrupole-Time of flight (UPLC-QTof) and nuclear magnetic resonance analysis.

Cardiovascular magnetic resonance characterization of a hamartoma in an asyntomatic child

Background The prevalence of primary cardiac neoplasms is approximately 0.3% and these masses should be distinguished from many of other primary and secondary processes that can occur in the heart. Further assessment of the left ventricular mass presents important clinical implications. Cardiovascular magnetic resonance was used. Clinical case An asyntomatic 12-year-old child was referred for cardiovascular magnetic resonance imaging to further assess a left ventricular mass found after an echocardiography, executed for assessment for sport activity. His past medical history was absolutely negative. The patient was in optimal state of health. The EKG showed an aspecific ST elevation. A hamartoma was diagnosed. A surgical approach was performed. After 7 days the patient is in good condition.

Solid-state nuclear magnetic resonance characterization of PE–PEG/silica hybrid materials prepared by microwave-assisted sol-gel process

Organic–inorganic hybrid materials were prepared by sol-gel processes starting from tetraethoxysilane (TEOS) and a triethoxysilane-terminated polyethylene–b-poly(ethylene glycol) copolymer (PE–PEG–Si). Curing of the initial reactant solution was carried out under different reaction conditions, and the materials so obtained were investigated by solid-state nuclear magnetic resonance (NMR). In particular, the molecular structure resulting from a conventional oven heating was compared with that obtained by unconventional microwave heating. The results highlighted that the extent of condensation reactions occurring over several hours under conventional heating is very similar to that resulting in 1 min under microwave heating. Additionally, 29Si–magic angle spinning (MAS) spectra showed that even though the overall extent of cross-linking in the inorganic network is only slightly affected by the thermal history of the sample, significantly different distributions of silicon sites can be present. 13C–CP/MAS selective spectra revealed the presence of PE “crystalline” domains within the organic phase, not detectable by differential scanning calorimetry (DSC). Finally, 1H–MAS spectra showed that different hydrogen-bond interactions are present in samples obtained under different curing conditions.

Steroidal isomers with uniform mass spectra of their per-TMS derivatives: Synthesis of 17-hydroxyandrostan-3-ones, androst-1-, and -4-ene-3,17-diols

In human sports doping control analysis most of the steroids are analyzed after enzymatic hydrolysis of the glucuronides as per-trimethylsilyl (TMS) derivatives applying gas chromatography–mass spectrometry (GC–MS). According to the recommendations of the World Anti-Doping Agency the identification of analytes should be based on retention time and on mass spectrometric characterization. This study shows that the bis-TMS derivatives of 16 specific C19 steroids, namely the stereoisomers of 5ξ-androst-1-ene-3ξ,17ξ-diol (8 isomers), androst-4-ene-3ξ,17ξ-diol (4 isomers), and 17ξ-hydroxy-5ξ-androstan-3-one (4 isomers), reveal very similar mass spectra. As a rule, when taking the retention times, which are provided as Kovac indices for all these isomers, into account, a restriction to two or three possible isomers is possible. Reliable identification should additionally include a comparison of the retention times of the analytes with the reference compounds measured concomitantly. In some cases standard addition may be appropriate. Due to the limited availability, the above mentioned isomers were synthesized by reduction of the corresponding α,β-unsaturated oxo steroids either with K-Selectride or by catalytic hydrogenation (Pd/C as catalyst). The products of the reactions were identified by means of nuclear magnetic resonance (NMR) characterization and by further reduction to the corresponding 5ξ-androstane-3ξ,17ξ-diols and GC–MS comparison with commercially available reference standards.

Proton Nuclear Magnetic Resonance Characterization of Resins from the Family Pinaceae

Proton magnetic resonance spectra were recorded for solutions of resinous materials harvested from 82 species in seven genera of the gymnospermous plant family Pinaceae. Data were recorded in both one and two (COSY) dimensions. Approximately 11 peaks in the 1D spectra and 10 cross-peaks in the 2D spectra were present in almost all pinacean spectra, providing a familial diagnostic. Some 40 1D peaks or peak clusters and 60 2D cross-peaks or clusters were considered significant and are reported, when present, for all species. Whereas previous solid-state 13C data were diagnostic primarily at the family level, the patterns of 1D and 2D peaks may provide diagnostic information at the genus and species levels. These spectra constitute the first broad use of 1H NMR to study plant exudates in general and to provide taxonomic characterization in particular.

Natural Weathering Evaluation of LDPE‐Mango Starch Blends by Mechanical Properties and High Field NMR

AbstractThe low‐density polyethylene/mango starch blends were obtained and submitted a natural degradation. Their mechanical properties and structures changes were determined by tensile, low and high field nuclear magnetic resonance characterization after different weathering times. The exposition time and starch content could be correlated to the polymer matrix changes from void formation theories. The blend deformations were affected by the starch degradation time. The starch degradation, confirmed by nuclear magnetic resonance, could be able to form voids and improve the blends fragmentability at relative low weathering times.

Low- and high-resolution nuclear magnetic resonance (NMR) characterisation of hyaluronan-based native and sulfated hydrogels

Hyaluronan-based hydrogels were synthesised using different crosslinking agents, such as 1,3-diaminopropane (1,3-DAP) and 1,6-diaminohexane (1,6-DAE). The hydrogels were sulfated to provide materials (Hyal-1,3-DAP, Hyal-1,6-DAE, HyalS-1,3-DAP and HyalS-1,6-DAE) that were characterised by both high- and low-resolution nuclear magnetic resonance (NMR) spectroscopy. The 13C NMR spectra of the materials were analysed to identify, characterise and study the crosslinking degree of the hydrogels. The crosslinking degree was also determined by potentiometric titration and the effectiveness of the two techniques was compared. Measurements of longitudinal relaxation times (spin–lattice) and of NOE enhancement were used to study the mobility of the hydrogels. Low-resolution NMR studies allowed the determination of the water transport properties in the hydrogels. In addition, the swelling degree for the various hydrogels was calculated as a function of the longitudinal and transversal relaxation times of the water molecules. Lastly, the self-diffusion coefficients of the water in interaction with the four polysaccharides were measured by the pulsed field gradient spin echo (PFGSE) sequence.

13Carbon nuclear magnetic resonance characterization of ethylene–propylene–1-octadecene terpolymers and comparison with ethylene–propylene–1-hexene and 1-decene terpolymers

In this paper, we report the complete 13C NMR characterization of a set of ethylene–propylene–1-octadecene terpolymers obtained with the metallocenic system rac-ethylene bis-indenyl zirconium dichloride, using different comonomer ratios. A detailed study of 13C NMR chemical shifts, triad sequence distributions, monomer average sequence lengths and reactivity ratios for these terpolymers is presented. The incorporations of 1-octadecene were superior of those obtained using 1-hexene and 1-decene in the same conditions. Catalytic activities of terpolymers of ethylene–propylene and α-olefins (α-olefins:1-hexene, 1-decene and 1-octadecene) were compared showing that they increase with the amount of propylene in the feed.

Magnetic Resonance Imaging and Characterization of Spontaneous Lesions in a Transgenic Mouse Model of Tuberous Sclerosis as a Model for Endothelial Cell-Based Transgene Delivery

Tuberous sclerosis (TSC) is an autosomal dominant genetic disorder characterized by abnormalities in cellular migration, proliferation, and differentiation in many tissues. Benign hamartomas develop in multiple organs, believed to be caused by somatic mutation in addition to germ line mutation to cause loss of both alleles of either the TSC1 or TSC2 tumor suppressor gene, with resultant dysregulated growth due to loss of hamartin or tuberin function, respectively. This study focuses on detecting spontaneous lesions in a knockout mouse model of TSC2 by magnetic resonance imaging (MRI) and exploring the efficiency of introducing gene products into lesions, using transduced endothelial cells as gene vehicles. MRI was shown to be effective in detecting spontaneous lesions in multiple tissues as a means of assessing the prevalence of tumors. Tsc(2+/) heterozygous mice were screened at 12-24 months of age. MRI detected 100% of the renal lesions (cystadenomas, renal cell carcinomas) and 75% of the hepatic lesions (hemangiosarcomas), later identified by histology. Cell-mediated gene delivery was evaluated by immunohistochemical analysis of renal, hepatic, and lung lesions after intravenous delivery of MS1 mouse endothelial cells, transduced to express an enhanced form of green fluorescent protein (EGFP). Preliminary immunohistochemical analysis, using a polyclonal antibody to EGFP and a horseradish peroxidase-diaminobenzidine detection system, revealed these cells throughout liver, kidney, and lung sections from injected animals, organs that are frequently affected in TSC2 patients, as well as within the lesions themselves.

Magnetic resonance characterization of tumor microvessels in experimental breast tumors using a slow clearance blood pool contrast agent (carboxymethyldextran-A2-Gd-DOTA) with histopathological correlation

Carboxymethyldextran (CMD)-A2-Gd-DOTA, a slow clearance blood pool contrast agent with a molecular weight of 52.1 kDa, designed to have intravascular residence for more than 1 h, was evaluated for its potential to characterize and differentiate the microvessels of malignant and benign breast tumors. Precontrast single-slice inversion-recovery snapshot FLASH and dynamic contrast-enhanced MRI using an axial T1-weighted three-dimensional spoiled gradient recalled sequence was performed in 30 Sprague-Dawley rats with chemically induced breast tumors. Endothelial transfer coefficient and fractional plasma volume of the breast tumors were estimated from MRI data acquired with CMD-A2-Gd-DOTA enhancement injected at a dose of 0.1 mmol Gd/kg body weight using a two-compartment bidirectional model of the tumor tissue. The correlation between MRI microvessel characteristics and histopathological tumor grade was determined using the Scarff-Bloom-Richardson method. Using CMD-A2-Gd-DOTA, no significant correlations were found between the MR-estimated endothelial transfer coefficient or plasma volumes with histological tumor grade. Analysis of CMD-A2-Gd-DOTA-enhanced MR kinetic data failed to demonstrate feasibility for the differentiation of benign from malignant tumors or for image-based tumor grading.

Isolated Ventricular Non-Compaction in Adults With Idiopathic Cardiomyopathy: Cardiac Magnetic Resonance and Pathologic Characterization of the Anomaly

Non-compaction of the ventricular myocardium is an anomaly of myocardial morphogenesis that leads to persistence of the embryonic myocardium with an excessively prominent trabecular meshwork and deep intertrabecular recesses. This report describes 3 cases of isolated left ventricular non-compaction in adults leading to terminal heart failure. We describe their distinctive myocardial histopathology and prospective diagnosis by cardiac magnetic resonance imaging (CMR). Heart transplantation was the only treatment option for all 3 of these severely ill patients. Isolated ventricular non-compaction should be considered in patients with severe idiopathic cardiomyopathy whose symptoms appear in early adulthood, and consideration given for early transplantation. Non-invasive imaging with CMR can confirm the diagnosis.

Characterization of brain tumors by MRS, DWI and Ki-67 labeling index

With the advent of fast imaging hardware and specialized software, additional non-invasive magnetic resonance characterization of tumors has become available through proton magnetic resonance spectroscopy (MRS), hemodynamic imaging and diffusion-weighted imaging (DWI). Thus, patterns could be discerned to discriminate different types of tumors and even to infer their possible evolution in time. The purpose of this study was to investigate the correlation between MRS, DWI, histopathology and Ki-67 labeling index in a large number of brain tumors. Localized proton spectra were obtained in 47 patients with brain tumors who subsequently underwent surgery (biopsy or tumor removal). We performed MRS with short echo-time (30 ms) and metabolic values in spectra were measured using an external software with 25 peaks. In all patients who had DWI, we measured apparent diffusion coefficients (ADC) in the same region of interest (ROI) where the voxel in MRS was located. In most tumors the histological diagnosis and Ki-67 labeling index had been determined on our original surgical specimen. Cho/Cr, (Lip+Mm)/Cr, NAA/(Cho+Cr) and Glx/Cr indexes in MRS allowed discriminating between low- and high-grade gliomas and metastases (MTs). Likewise, absolute ADC values differentiated low- from high-grade gliomas expressed by Ki-67 labeling index. A novel finding was that high Glx/Cr in vivo MRS index (similar to other known indexes) was a good predictor of tumor grading.

Nuclear Magnetic Resonance Characterization of the Refolding Intermediate of β 2-Microglobulin Trapped by Non-native Prolyl Peptide Bond

beta(2)-Microglobulin (beta2-m), a light chain of the major histocompatibility complex type I, is also found as a major component of amyloid fibrils formed in dialysis-related amyloidosis. Denaturation of beta2-m is considered to initiate the formation of fibrils. To clarify the mechanism of fibril formation, it is important to characterize the intermediate conformational states at the atomic level. Here, we investigated the refolding of beta2-m from the acid-unfolded state by heteronuclear magnetic resonance and circular dichroism spectroscopies. At low temperature, beta2-m refolded slowly, accumulating a rate-limiting intermediate with non-native chemical shift dispersions for several residues, but with compactness and secondary structures similar to those of the native protein. beta2-m has a cis proline residue at Pro32, located on the turn connecting the betaB and betaC strands. The slow refolding phase disappeared upon mutation of Pro32 to Val, indicating that Pro32 is responsible for the accumulation of the intermediate. The distribution of the perturbed residues in the intermediate suggests that the non-native prolyl peptide bond of Pro32 affects large areas of the molecule. A cis proline residue is common to various immunoglobulin domains involved in amyloidosis, implying that a non-native prolyl peptide bond that might occur under physiological conditions is related to the amyloidogenicity of these immunoglobulin domains.

Quantitative nuclear magnetic resonance analysis and characterization of the derivatized Haemophilus influenzae type b polysaccharide intermediate for PedvaxHIB

PedvaxHIB is a pediatric vaccine that protects children from severe disease caused by the gram-negative bacterium Haemophilus influenzae type b (Hib). The vaccine is made by chemically conjugating Hib capsular polysaccharide to the outer membrane protein complex of Neisseria meningitidis. The protein-conjugated vaccine has proven to be extremely effective in preventing invasive Hib disease in infants and young children. This paper presents the nuclear magnetic resonance (NMR) methodology for the quantitative characterization of derivatized polysaccharide and its validation closely following ICH guidelines. The assay has been shown to be precise and accurate (relative standard deviation [RSD] ⩽1%), specific (no observable matrix interference), rugged (RSD <3% for day-to-day and operator-to-operator variations), and robust (to changes in temperature and polysaccharide concentration). Therefore, the quantitative NMR assay can be used as a reliable product release or process monitoring method and can replace several labor-intensive chromatographic and colorimetric methods.

Structural and magnetoelectric properties of MFe 2 O 4 ?PZT (M?=?Ni,Co) and La x (Ca,Sr) 1-x MnO 3 ?PZT multilayer composites

Thick-film layered magnetoelectric composites consisting of ferromagnetic and ferroelectric phases have been synthesized with nickel ferrite (NFO), cobalt ferrite, La0.7Sr0.3MnO3 (LSMO), or La0.7Ca0.3MnO3 (LCMO) and lead zirconate titanate (PZT). Structural, magnetic, and ferromagnetic resonance characterization shows evidence for defect-free ferrites, but deterioration of manganite parameters. The resistivity and dielectric constants are smaller than expected values. The magnetoelectric effect (ME) is stronger in ferrite–PZT than in manganite–PZT. The ME voltage coefficient αE at room temperature is the highest in NFO–PZT and the smallest for LCMO–PZT. The transverse ME effect is an order of magnitude stronger than the longitudinal effect. The magnitude of αE correlates well with magnetic permeability for the ferrites.

Chemical and carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance characterization of logyard fines from British Columbia.

Phasing out beehive burners and rising costs for landfilling have increased the need to widen options for utilization of the smaller size fractions of woody wastes generated during log handling and sawmilling in British Columbia. We characterized several size classes of logyard fines up to 16 mm sampled from coastal and interior operations. Total C, total N, ash, and condensed tannin concentrations were consistent with properties derived largely from wood, with varying proportions of bark and mixing with mineral soil. Especially for < 3-mm fractions, the latter resulted in high ash contents that would make them unsuitable for fuel. Solid-state 13C cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra were consistent with the chemical data, with high O-alkyl intensity and similarity to naturally occurring woody forest floor; no samples were high in aromatic or phenolic C. Aqueous extracts of two < 16-mm fines, which accounted for only a small proportion of the total C, were enriched in alkyl C and had low or undetectable tannins. Application to forest sites might cause short-term immobilization of N, but also might include possible longer-term benefits from reduction of N loss after harvesting and restoration of soil organic matter in degraded sites.

Chemical and Carbon-13 Cross-Polarization Magic-Angle Spinning Nuclear Magnetic Resonance Characterization of Logyard Fines from British Columbia

Chemical and Carbon-13 Cross-Polarization Magic-Angle Spinning Nuclear Magnetic Resonance Characterization of Logyard Fines from British Columbia

Photocleavage of Pyridyl-Based Aromatic Polyureas

The photophysical properties of a metal chelating pyridyl-based aromatic ureas and poly(1,4-phenylene-2,6-pyridylurea) were investigated. In their solution state and upon exposure to 365 nm UV radiation, these low and high molecular weight compounds were found to cleave the urea linkage nearly quantitatively, generating the corresponding amine-terminated subunits and CO2. Through a series of model compounds along with nuclear magnetic resonance (NMR), UV/vis absorption, and fluorescence spectroscopy characterization, the photocleavage process was delineated as a function of UV dose, O2, and water. The presence of water was found crucial to this photocleavage process with O2 playing a role only in subsequent oxidation of resulting amine functionalities. The experimental results support a light-assisted hydrolysis of the urea bond as the most plausible photocleavage mechanism. The photocleavage of such pyridyl-based ureas can potentially find usages in light-assisted base generation and/or for releasing metal cations.

377 Nuclear magnetic resonance detection and characterisation of liver steatosis in rats

The decreased tolerance of steatotic livers to warmischemia complicates liver surgery. The efficacy of heatshock preconditioning in steatotic livers to lessenischemia–reperfusion injury was studied in rats. Steatotic liver was produced in Lewis rats with a choline-deficient diet. Rats with steatotic livers were divided into a heat shock preconditioned group (group HS) and a controlgroup (group C). All rats received 45 min of hepaticwarm ischemia. Survival rates and changes in biochemical and histological parameters were compared in both groups. Heat shock protein 72 (HSP72) was produced only in group HS. The 7-day survival of the rats after warm ischemic intervention was significantly better in group HS (13/15) than in group C (5/15) (P< 0.01). The concentration of ATP in liver tissue (n= 10,P< 0.01) and serum levels of aspartate aminotransferase (n= 10,P< 0.05), alanine aminotransferase (n= 10,P< 0.01), and lactic dehydrogenase (n= 10,P< 0.01) at 40 min reperfusion were also significantly better in group HS than in group C. Histological examination at 40 min reperfusion showed severe sinusoidal congestion, hepatocyte necrosis, and increased positivity to 4-hydroxy-2-nonenal-modified proteins in group C livers; these signs were markedly suppressed in group HS livers. The data indicate that heat shock preconditioning provides the steatotic rat liver with significant tolerance to warm ischemia–reperfusion injury.

Multinuclear Magnetic Resonance Characterization of Solid Catalysts and Their Reactions in the Adsorbed State

AbstractFor Abstract see ChemInform Abstract in Full Text.