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Karel Heremans - One of the best experts on this subject based on the ideXlab platform.
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hydration behaviour of popc c12 bet mixtures investigated by sorption gravimetry 31P NMR Spectroscopy and x ray diffraction
Chemistry and Physics of Lipids, 2012Co-Authors: Helge Pfeiffer, Heiko Weichert, Gotthard Klose, Karel HeremansAbstract:Abstract The hydration behaviour of mixtures of the zwitterionic phospholipid 1-palmitoyl-2-oleolyl-sn-glycero-3-phosphocholine (POPC) and the zwitterionic surfactant N,N-dimethyl-N-dodecyl-betain (C12-Bet) was investigated by sorption gravimetry, solid-state 31P NMR-Spectroscopy and small angle X-ray diffraction (SAXD). Negative excess hydration (dehydration) was found for almost all hydration degrees investigated. This behaviour is explained by the formation of an inner salt between the dipoles of phospholipid and surfactant headgroups that show a reverse sequence of partial charges with respect to the hydrocarbon backbone. The formation of an inner-salt most probably reduces potential water binding sites. Moreover, NMR data suggest that the incorporation of the zwitterionic surfactant into the phospholipid membrane is correlated with reorientation of the phosphate axis towards the membrane director as well as with reduced lateral and wobbling diffusion.
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Hydration behaviour of POPC/C12-Bet mixtures investigated by sorption gravimetry, 31P NMR Spectroscopy and X-ray diffraction
Chemistry and Physics of Lipids, 2012Co-Authors: Helge Pfeiffer, Heiko Weichert, Gotthard Klose, Karel HeremansAbstract:Abstract The hydration behaviour of mixtures of the zwitterionic phospholipid 1-palmitoyl-2-oleolyl-sn-glycero-3-phosphocholine (POPC) and the zwitterionic surfactant N,N-dimethyl-N-dodecyl-betain (C12-Bet) was investigated by sorption gravimetry, solid-state 31P NMR-Spectroscopy and small angle X-ray diffraction (SAXD). Negative excess hydration (dehydration) was found for almost all hydration degrees investigated. This behaviour is explained by the formation of an inner salt between the dipoles of phospholipid and surfactant headgroups that show a reverse sequence of partial charges with respect to the hydrocarbon backbone. The formation of an inner-salt most probably reduces potential water binding sites. Moreover, NMR data suggest that the incorporation of the zwitterionic surfactant into the phospholipid membrane is correlated with reorientation of the phosphate axis towards the membrane director as well as with reduced lateral and wobbling diffusion.
Benjamin L. Turner - One of the best experts on this subject based on the ideXlab platform.
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phosphorus speciation in temperate basaltic grassland soils by solution 31P NMR Spectroscopy
European Journal of Soil Science, 2009Co-Authors: P N C Murphy, Andrew Bell, Benjamin L. TurnerAbstract:Summary Phosphorus (P) speciation in 21 basaltic and four non-basaltic Irish grassland soils was determined by NaOH–EDTA extraction and 31P NMR Spectroscopy. Organic P in basaltic soils ranged between 30 and 697 mg P kg−1 and consisted of phosphate monoesters (84–100%), DNA (0–16%) and phosphonates (0–5%). Inorganic P was mainly phosphate (83–100%) with small concentrations of pyrophosphate (0–17%). Phosphate monoesters were more important as a proportion of extracted P in basaltic soils, probably because of their greater oxalate-extractable Fe and Al contents. Phosphate monoesters appeared to be strongly associated with non-crystalline Al and increased with total soil P concentration, indicating that they do accumulate in grassland soils. In non-basaltic soils myo-inositol hexakisphosphate constituted between 20 and 52% of organic P, while scyllo-inositol hexakisphosphate constituted between 12 and 17%. These compounds were not quantified separately in basaltic soils because of poor NMR resolution in the phosphate monoester region, but appeared to represent a considerable proportion of the organic P in most samples. DNA concentrations were greater in basaltic soils compared with non-basaltic soils and were associated with acidic pH and large total C contents. The inability of the Olsen P test to assess effectively the P status of basaltic soils may result from strong phosphate sorption to Fe and Al oxides, inducing plant utilization of soil organic P. Phosphorus nutrient management should account for this to avoid over-application of P and associated financial and environmental costs.
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soil organic phosphorus in tropical forests an assessment of the naoh edta extraction procedure for quantitative analysis by solution 31P NMR Spectroscopy
European Journal of Soil Science, 2008Co-Authors: Benjamin L. TurnerAbstract:Summary The extraction of soil organic phosphorus by the NaOH–EDTA procedure was assessed in detail for a tropical forest soil (clay-loam, pH 4.3, total carbon 2.7%). Optimum conditions for the quantification of soil organic phosphorus and characterization of its composition by solution 31P NMR Spectroscopy were extraction in a solution containing 0.25 m NaOH and 50 mm Na2EDTA in a 1:20 solid to solution ratio for 4 hours at ambient laboratory temperature. Replicate analyses yielded a coefficient of variation of 3% for organic phosphorus as a proportion of the spectral area. There was no significant difference in total phosphorus extraction from fresh and air-dried soil, although slightly more organic phosphorus and less paramagnetic ions were extracted from dried soil. The procedure was not improved by changing the concentration of NaOH or EDTA, extraction time, or solid to solution ratio. Pre-extraction with HCl or Na2EDTA did not increase subsequent organic phosphorus extraction in NaOH–EDTA or improve spectral resolution in solution 31P NMR Spectroscopy. Post-extraction treatment with Chelex resin did not improve spectral resolution, but removed small concentrations of phosphorus from the extracts. Increasing the pH of NaOH–EDTA extracts (up to 1.0 m NaOH) increased the concentration of phosphate monoesters, but decreased DNA to an undetectable level, indicating its hydrolysis in strong alkali. The standardized NaOH–EDTA extraction procedure is therefore recommended for the analysis of organic phosphorus in tropical forest soils.
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Quantification of myo-inositol hexakisphosphate in alkaline soil extracts by solution 31P NMR Spectroscopy and spectral deconvolution
Soil Science, 2003Co-Authors: Benjamin L. Turner, N. Mahieu, Leo M. CondronAbstract:Inositol phosphates are the dominant class of organic phosphorus (P) compounds in most soils, but are poorly understood because they are not easily identified in soil extracts. This study reports a relatively simple technique using solution 31P NMR Spectroscopy and spectral deconvolution for the qua
Céline Moreau - One of the best experts on this subject based on the ideXlab platform.
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Identification and quantification of phosphorus in cheeses - methodological investigations by solid-state 31P NMR Spectroscopy
2008Co-Authors: Corinne Rondeau-mouro, Mallory Gobet, Bernard Mietton, Solange Buchin, Céline MoreauAbstract:NMR has been shown to be an interesting tool for investigating dairy foods, in particular cheese products, for which the method is non-destructive and well suited for investigating their compounds showing different structure and mobility during ripening. Solid-state magic angle spinning 31P NMR Spectroscopy was used to characterize the structure and composition of semi-hard cheeses. Assignment including overlapping resonances from mobile/immobile phosphorylated serine residues and inorganic calcium phosphates, has been realised using different NMR techniques (spin echo, cross polarisation and single pulse excitation) and by comparison with spectra of literature. Studies at various ripening stages and salt contents have been achieved in order to understand the impact of salt on the phosphates structures and mobility within the cheese matrix, as well as its influence in enzymatic activities.
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Sarcolemma phospholipid structure investigated by immunogold electron microscopy and 31P NMR Spectroscopy with lanthanide ions
FEBS Letters, 2001Co-Authors: Céline Moreau, J. Segalen, G. Leray, Annie Cavalier, Marie Le Floch, Chantal Rocher, Mounir Traı̈kia, Arnaud Bondon, Daniel Thomas, E. Le RumeurAbstract:Abstract The biological functions of plasma membranes depend greatly on the biophysical properties resulting from protein and phospholipid structure. We investigated the phospholipid structure of the normal sarcolemma membrane, which is known to be highly dysfunctional in myopathies. Combining electron microscopy and 31P nuclear magnetic resonance (NMR) Spectroscopy on isolated sarcolemma vesicles, we find that (i) the sarcolemma vesicles maintain the in-vivo cellular sidedness, (ii) the phospholipid mobility is close to that observed in model membranes (similar lateral diffusion coefficients and spin–lattice T1 relaxation times). Using broad-band and magic angle spinning 31P NMR Spectroscopy with lanthanide ions (Pr3+), it is possible to quantify the distribution of phospholipids between internal and external membrane layers, showing that the trans-bilayer distribution is highly asymmetrical.
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Static and magic angle spinning 31P NMR Spectroscopy of two natural plasma membranes
FEBS Letters, 1999Co-Authors: Céline Moreau, M. Le Floc'h, J. Segalen, G. Leray, Laurent Metzinger, J. D. De Certaines, E. Le RumeurAbstract:Abstract Static and magic angle spinning 31P NMR Spectroscopy was used for the first time in natural plasma membranes from erythrocytes and skeletal muscle to study phospholipid arrangement and composition. Typical static powder-like spectra were obtained showing that phospholipids were in a bilayer arrangement. Magic angle spinning narrowed spectra into two components. The first one corresponded to phosphatidylcholine and the second one to the other phospholipids with intensities in agreement with the known phospholipid composition. These findings show that NMR data previously acquired using model membranes can be transposed to studies on phospholipids in their natural environment.
Robert E. Mrak - One of the best experts on this subject based on the ideXlab platform.
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Phospholipid composition of postmortem schizophrenic brain by 31P NMR Spectroscopy.
Magnetic Resonance in Medicine, 2008Co-Authors: John M. Pearce, Richard A. Komoroski, Robert E. MrakAbstract: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 hexane-isopropanol, 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
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31P NMR Spectroscopy of phospholipid metabolites in postmortem schizophrenic brain.
Magnetic Resonance in Medicine, 2008Co-Authors: Richard A. Komoroski, John M. Pearce, Robert E. MrakAbstract: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.
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Determination of water content in olive oil by 31P NMR Spectroscopy.
Journal of Agricultural and Food Chemistry, 2008Co-Authors: Emmanuel Hatzakis, Photis DaisAbstract: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.
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Determination of Phospholipids in Olive Oil by 31P NMR Spectroscopy
Journal of Agricultural and Food Chemistry, 2008Co-Authors: Emmanuel Hatzakis, Anastasios Koidis, Dimitrios Boskou, Photis DaisAbstract: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 acid composition in phospholipids and triacylglycerols of olive oil was similar.
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Determination of Glycerol in Wines Using ^31P-NMR Spectroscopy
Journal of the American Oil Chemists' Society, 2007Co-Authors: Emmanuel Hatzakis, Eleftherios Archavlis, Photis DaisAbstract:^31P-NMR 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 ^31P-NMR 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.
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Determination of Glycerol in Wines Using 31P‐NMR Spectroscopy
Journal of the American Oil Chemists' Society, 2007Co-Authors: Emmanuel Hatzakis, Eleftherios Archavlis, Photis DaisAbstract:31P-NMR 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 31P-NMR 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.
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Application of 31P NMR Spectroscopy in Food Analysis. 1. Quantitative Determination of the Mono- and Diglyceride Composition of Olive Oils
Journal of Agricultural and Food Chemistry, 2000Co-Authors: Apostolos Spyros, Photis DaisAbstract:This paper introduces a facile method to determine the amount of mono- and diglycerides in virgin olive oils. This method is based on the phosphorylation of the free hydroxyls of the mono- and diglycerides with 2-chloro-4,4,5,5-tetramethyldioxaphospholane and the integration of the appropriate peaks in the 31P NMR spectrum. Quantitative 31P NMR Spectroscopy can be extended to the quantification of other constituents of olive oils bearing functional groups with labile protons. Keywords: Olive oil; 31P NMR; monoglycerides; diglycerides
