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31P NMR Spectroscopy

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Karel Heremans – One of the best experts on this subject based on the ideXlab platform.

Benjamin L. Turner – One of the best experts on this subject based on the ideXlab platform.

Céline Moreau – One of the best experts on this subject based on the ideXlab platform.

Robert E. Mrak – One of the best experts on this subject based on the ideXlab platform.

  • Phospholipid composition of postmortem schizophrenic brain by 31P NMR Spectroscopy.
    Magnetic Resonance in Medicine, 2008
    Co-Authors: John M. Pearce, Richard A. Komoroski, Robert E. Mrak
    Abstract:

    Cell membrane abnormalities due to changes in phospholipid (PL) composition and metabolism have been implicated in schizophrenia pathogenesis. That work has generally assessed membrane phospholipids from non-neural tissues such as erythrocytes and platelets. High resolution 31P NMR Spectroscopy was used to characterize PLs of gray matter in postmortem brain for 20 schizophrenics, 20 controls, and 7 patients with other mental illnesses (psychiatric controls). Tissues from frontal, temporal, and occipital cortices were extracted with hexaneisopropanol, and 31P NMR spectra were obtained in an organic-solvent system to resolve the major PL classes (based on headgroups) and subclasses (based on linkage at the sn-1 position). Surprisingly, repeated-measures multivariate analysis of variance revealed no overall differences among the groups. There were no significant differences (p

  • 31P NMR Spectroscopy of phospholipid metabolites in postmortem schizophrenic brain.
    Magnetic Resonance in Medicine, 2008
    Co-Authors: Richard A. Komoroski, John M. Pearce, Robert E. Mrak
    Abstract:

    Evidence has been accumulating that schizophrenia involves abnormalities in the composition and metabolism of cell membrane phospholipids (PLs) in the brain. In vivo 31P MRS has been used to measure the metabolic precursors and degradation products of PL metabolism in schizophrenia. Because in vivo line widths are substantially broader than in solution, only the broad phosphomonoester (PME) and phosphodiester bands, or partly resolved resonances of individual metabolites, are typically measured in vivo in the 31P spectrum. In addition to poor resolution, the relatively low signal-to-noise ratio (SNR) makes precise quantitation difficult. An alternative with substantially better resolution and precision for quantitation is high-resolution NMR Spectroscopy of extracts of samples from postmortem brain. Here we determine absolute concentrations of the individual PL metabolites phosphocholine (pc), phosphoethanolamine (pe), glycerophosphocholine (gpc), and glycerophosphoethanolamine in aqueous extracts of tissue from frontal, temporal, and occipital cortex of postmortem brain for schizophrenics, controls, and patients with other mental illnesses (psychiatric controls [PC]) using high-resolution 31P NMR Spectroscopy. For the complete groups, which included both males and females, there were no statistically significant differences for schizophrenics vs. controls for any of the four PL metabolites in any of the three brain regions. Trends (0.05 < P < 0.10) were noted for increased gpc in schizophrenia in all three regions. PC differed from both controls and schizophrenics in several measures. When only males were considered, gpc was significantly (P < 0.05) elevated in all three brain regions in schizophrenia. Magn Reson Med 59:469–474, 2008. © 2008 Wiley-Liss, Inc.

Photis Dais – One of the best experts on this subject based on the ideXlab platform.

  • Determination of water content in olive oil by 31P NMR Spectroscopy.
    Journal of Agricultural and Food Chemistry, 2008
    Co-Authors: Emmanuel Hatzakis, Photis Dais
    Abstract:

    A method for moisture determination in olive oil using 31P NMR Spectroscopy is developed. This method is based on the replacement of the hydrogen atoms of water molecules with the tagging agents 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane and diphenylphosphinic chloride. Both reagents were successful in determining moisture in olive oil. However, only the second reagent provided a clean and instantaneous reaction under mild condition with no side reactions as observed with the first reagent. A study comparison was made to assess the agreement between the present analytical NMR method and the well-established methods of Karl Fischer titration.

  • Determination of Phospholipids in Olive Oil by 31P NMR Spectroscopy
    Journal of Agricultural and Food Chemistry, 2008
    Co-Authors: Emmanuel Hatzakis, Anastasios Koidis, Dimitrios Boskou, Photis Dais
    Abstract:

    A nondestructive analytical method based on NMR Spectroscopy was developed for the determination of phospholipids in olive oil. The phospholipids extracted from virgin olive oil with a mixture of ethanol/water (2:1 v/v) were identified and quantified by high resolution 31P NMR Spectroscopy. The main phospholipids found in olive oil were phosphatidic acid, lyso-phosphatidic acid, and phosphatidylinositol. Validation of the 31P NMR methodology for quantitative analysis of phospholipids in olive oil was performed. Sensitivity was satisfactory with detection limits of 0.25−1.24 μmol /mL. In addition, the composition of fatty acids in phospholipids model compounds and those in olive oil samples was estimated by employing one- and two-dimensional 1H NMR. The results indicated that the fatty acidacid composition in phospholipids and triacylglycerols of olive oil was similar.

  • Determination of Glycerol in Wines Using ^31PNMR Spectroscopy
    Journal of the American Oil Chemists' Society, 2007
    Co-Authors: Emmanuel Hatzakis, Eleftherios Archavlis, Photis Dais
    Abstract:

    ^31PNMR Spectroscopy was employed to detect and quantify glycerol in red wines from various regions of Greece. This novel analytical method was based on the derivatization of the hydroxyl groups of glycerol with 2-chloro-4,4,5,5-tetramethyl dioxaphospholane, and identification of the phosphitylated compound on the basis of ^31P chemical shifts. Quantification of glycerol in wines was accomplished by integration of appropriate signals in the ^31PNMR spectrum and the use of the phosphitylated cyclohexanol as the internal standard. The method was reproducible (CV (%) = 2.35) and accurate (CV (%) = 1.34). Its applicability to glycerol quantification in wines was tested against a weighted amount of a glycerol-model compound by linear regression analysis ( R  = 0.999; intercept = 0.074 ± 0.078; slope = 0.998 ± 0.003; p  = 0.000). Furthermore, the NMR method was compared to the AOAC official method (HPLC) using the Bland and Altman statistical analysis. The distribution of the data points in the bias plot showed that 100% of the measurements of glycerol in 16 wine samples from various regions of Greece were within the limits of agreement of the two methods.