Angle Spinning Magnetic Resonance Spectroscopy Research Articles

Evaluation of Tissue Metabolites with High Resolution Magic Angle Spinning MR Spectroscopy Human Prostate Samples after Three-Year Storage at –80 °C

Accurate interpretation and correlation of tissue spectroscopy with pathological conditions requires disease-specific tissue metabolite databases; however, specimens for research are often kept in frozen storage for various lengths of time. Whether such frozen storage results in alterations to the measured metabolites is a critical but largely unknown issue. In this study, human prostate tissues from specimens that had been stored at –80 °C for 32 months were analyzed with high resolution magic angle spinning (HRMAS) magnetic resonance (MR) spectroscopy, and compared with the initial measurements of the adjacent specimens from the same cases when snap frozen in the operation room and kept frozen for less than 24 hours. Results of the current study indicate that that the storage-induced metabolite alterations are below the limits that tissue MR spectroscopy can discriminate. Furthermore, quantitative pathology evaluations suggest the observed alterations in metabolite profiles measured from the adjacent specimens of the same prostates may be accounted for by tissue pathological heterogeneities and are not a result of storage conditions. Hence, these results indicate that long-term frozen storage of prostate specimens can be quantitatively analyzed by HRMAS MR spectroscopy without concerns regarding significant metabolic degradation or alteration.

MR-determined metabolic phenotype of breast cancer in prediction of lymphatic spread, grade, and hormone status

The purpose of the study was to evaluate the use of metabolic phenotype, described by high-resolution magic angle spinning magnetic resonance spectroscopy (HR MAS MRS), as a tool for prediction of histological grade, hormone status, and axillary lymphatic spread in breast cancer patients. Biopsies from breast cancer (n = 91) and adjacent non-involved tissue (n = 48) were excised from patients (n = 77) during surgery. HR MAS MR spectra of intact samples were acquired. Multivariate models relating spectral data to histological grade, lymphatic spread, and hormone status were designed. The multivariate methods applied were variable reduction by principal component analysis (PCA) or partial least-squares regression-uninformative variable elimination (PLS-UVE), and modelling by PLS, probabilistic neural network (PNN), or cascade correlation neural network. In the end, model verification by prediction of blind samples (n = 12) was performed. Validation of PNN training resulted in sensitivity and specificity ranging from 83 to 100% for all predictions. Verification of models by blind sample testing showed that hormone status was well predicted by both PNN and PLS (11 of 12 correct), lymphatic spread was best predicted by PLS (8 of 12), whereas PLS-UVE PNN was the best approach for predicting grade (9 of 12 correct). MR-determined metabolic phenotype may have a future role as a supplement for clinical decision-making-concerning adjuvant treatment and the adaptation to more individualised treatment protocols.

Quantitative Pathology in Tissue MR Spectroscopy Based Human Prostate Metabolomics

At present, the clinical utility of metabolomic profiles of human prostate tissue relies on the establishment of correlations between metabolite data and clinical measurements, particularly pathological findings. Because metabolomics is a quantitative study, its clinical value can be rigorously investigated by determining its association with other quantitative measures. The human visual assessment of prostate tissue, however, introduces both inter- and intra-observer biases that may limit the reliability of its quantitations, and therefore, the strength of its correlations with metabolomic profiles. The aim of this study was to develop a simple, feasible protocol for the computer-aided image analysis (CAIA) of prostate pathology slides in order to achieve quantitative pathology from tissue samples, following metabolomic measurement with high-resolution magic angle spinning (HRMAS) magnetic resonance spectroscopy (MRS). Thirty-eight samples from 29 prostatectomy cases were studied with HRMAS MRS. After spectroscopy analysis, samples were serial-sectioned, stained and visually assessed by pathologists. Cross-sections from these samples were then measured with the CAIA protocol. Results showed a two-fold difference between human visual assessments of the area percentages of tissue pathologies and CAIA area percentages obtained for the same features. Linear correlations were found between both metabolites indicative of normal epithelium and those indicative of prostate cancer, and the CAIA quantitative results. CAIA based quantitative pathology is more reliable than human visual assessment in establishing correlations useful for disease diagnosis between prostate pathology and metabolite concentrations.

Solid‐state NMR study of [(Ph3SnF)2(Ph3SnO2PPh2)], a novel coordination polymer prepared from Bu4N[Ph3SnF2] and [Ph3SnOPPh2OSnPh3](O3SCF3)

AbstractThe coordination polymer [(Ph3SnF)2(Ph3SnO2PPh2)] (3), prepared by the reaction of [Ph3SnOPPh2OSnPh3](O3SCF3) (4) with Bu4N[Ph3SnF2] (5), was investigated by multinuclear magic angle spinning magnetic resonance spectroscopy and the results compared with those of the polymeric parent compounds Ph3SnF (1) and Ph3SnO2PPh2 (2). The crystal structure of 4 was determined by X‐ray crystallography. Copyright © 2004 John Wiley & Sons, Ltd.

A combined use of 13C-cross polarization/magic angle spinning, 13C-magic angle spinning and 31P-nuclear magnetic resonance spectroscopy with differential scanning calorimetry to study cannabinoid-membrane interactions

We have examined and compared the thermotropic and dynamic properties of cannabimimetic (-)-Δ 8-tetrahydrocannabinol (Δ 8-THC) and its biologically almost inactive analog (-)-O-methyl-Δ 8-tetrahydrocannabinol (Me-Δ 8-THC) using non spinning 31 P and high resolution 13 C solid state NMR spectroscopy in combination with DSC (Differential Scanning Calorimetry) in dipalmitoylphosphatidylcholine (DPPC) bilayers. DSC traces showed that cannabinoids broaden the phase transition and shift the phase transition temperature of DPPC bilayers to lower temperatures and the active one produces more significant lowering and broadening. The DSC results also showed that Me-Δ 8-THC lowers and broadens the pretransition area. However, the severe broadening of the phase transition in the thermogram of DPPC/Δ 8-THC did not allow any conclusive results for its effect in the pretransition area. 13C and 31P-NMR data were used to complement this information. 13C-NMR spectroscopy appeared very sensitive to detect conformational changes in the pretransition area when the chemical shift changes of the observed peaks in the hydrophobic region were studied versus temperature increase. The obtained results confirmed DSC data for DPPC/Me-Δ 8-THC preparation and showed no visible pretransition for DPPC/Δ 8-THC sample. 13C-NMR spectroscopy gave direct evidence of the intercalation of both molecules into the membrane bilayers due to the specific additional peaks appeared in the DPPC/Δ 8-THC and DPPC/Me-Δ 8-THC preparations. The specific additional peaks appeared in the 13C-CP/MAS and MAS spectra when each of the cannabinoids was present in the preparation indicates a different mobility of the corresponding molecular moiety in the phospholipid bilayer environment. 31P-NMR spectroscopy revealed that the presence of the active analog causes significant conformational changes in the vicinity of the headgroup while the almost inactive analog only minor changes. These data suggest that the almost inactive cannabinoid intercalates in the hydrophobic region of the membrane bilayer while the active one in the backbone and polar region. In conclusion, the obtained results show that phospholipid–cannabinoid interactions of the studied pair of analogs differ and therefore may related to their different biological activities.

The 3'-keto-diol equilibrium of trospectomycin sulfate bulk drug and freeze-dried formulation: solid-state carbon-13 cross-polarization magic angle spinning (CP/MAS) and high-resolution carbon-13 nuclear magnetic resonance (NMR) spectroscopy studies.

Understanding how moisture interacts with a drug or formulation is a critical component of product development. This study demonstrates how water affects the 3'-gem-diol<==>3'-keto equilibrium in trospectomycin sulfate bulk drug and freeze-dried formulation, as probed by solid-state carbon-13 cross-polarization magic angle spinning (CP/MAS) and high-resolution nuclear magnetic resonance (NMR) spectroscopy. Drying the bulk drug or formulation to low water levels dehydrates trospectomycin sulfate from the diol to the keto form. Carbon-13 CP/MAS NMR spectroscopy measures the keto drug concentration in solid samples directly. The bulk drug, which contains approximately 16% water, is more than 90% in the 3'-diol form. Oven drying to < 3% water converts approximately 75% of the drug to the 3'-keto form. The drug is formulated as a freeze-dried, sterile powder that can contain up to 12% water depending on the freeze-drying conditions. These studies show that the 3'-keto concentration rises uniformly (up to 75%) with decreasing residual water in the freeze-dried cake. The keto-diol equilibrium was also studied in solution by high-resolution carbon-13 NMR experiments, and it was found that raising the temperature or using dimethyl sulfoxide (DMSO) as a solvent also dehydrates the drug. For example, in aqueous solution at 25 degrees C, nearly all (> 95%) of the drug is in the 3'-diol form. After equilibration at 60 degrees C, however, the 3'-keto content increases to 7%, and in d6-DMSO solvent at 25 degrees C the drug is mostly (60%) in the 3'-keto form.

High-resolution oxygen-17 NMR of solid silicates

Several{sup 17}O-enriched silicates were studied by use of dynamic angle spinning (DAS) and double rotation (DOR) nuclear magnetic resonance spectroscopy. These methods average away second-order quadrupolar interactions by reorienting a sample about a time-dependent axis, thereby yielding high-resolution spectra of oxygen-17 nuclei. A narrow spectral line is observed for each distinct oxygen site at the sum of the isotropic chemical shift and the field-dependent isotropic second-order quadrupolar shift. Resolution is increased by up to 2 orders of magnitude compared to conventional magic angle spinning (MAS) spectra. Crystallographically inequivalent oxygen are now observable as distinct resonances in spectra of polycrystalline silicates such as diopside (CaMgSi{sub 2}{sup 17}O{sub 6}), wollastonite (CaSi{sup 17}O{sub 3}), larnite (Ca{sub 2}Si{sup 17}O{sub 4}), and forsterite (Mg{sub 2}Si{sup 17}O{sub 4}).