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31P NMR Spectrum

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

  • Detection and Quantification of Free Glycerol in Virgin Olive Oil by ^31PNMR Spectroscopy
    Journal of the American Oil Chemists' Society, 2010
    Co-Authors: Emanuel Hatzakis, Alexia Agiomyrgianaki, Photis Dais
    Abstract:

    ^31PNuclear magnetic resoresonance (NMR) spectroscopy was employed to detect and quantify free glycerol in virgin olive oils originating from various regions of Greece. This analytical method was based on the derivatization of the hydroxyl groups of glycerol with the tagging reagent 2-chloro-4,4,5,5-tetramethyldioxaphospholane, and identification of the phosphitylated compound on the basis of ^31P chemical shifts. Quantification of glycerol in olive oils was accomplished by integration of the appropriate signals in the ^31P NMR Spectrum and the use of the phosphitylated cyclohexanol as internal standard. A linear correlation was observed between the glycerol content and 1,3-diacylglycerols and free acidity indicating that glycerol is the final product of the partial hydrolysis of triacylglycerols.

  • Detection and Quantification of Free Glycerol in Virgin Olive Oil by 31PNMR Spectroscopy
    Journal of the American Oil Chemists' Society, 2009
    Co-Authors: Emanuel Hatzakis, Alexia Agiomyrgianaki, Photis Dais
    Abstract:

    31PNuclear magnetic resoresonance (NMR) spectroscopy was employed to detect and quantify free glycerol in virgin olive oils originating from various regions of Greece. This analytical method was based on the derivatization of the hydroxyl groups of glycerol with the tagging reagent 2-chloro-4,4,5,5-tetramethyldioxaphospholane, and identification of the phosphitylated compound on the basis of 31P chemical shifts. Quantification of glycerol in olive oils was accomplished by integration of the appropriate signals in the 31P NMR Spectrum and the use of the phosphitylated cyclohexanol as internal standard. A linear correlation was observed between the glycerol content and 1,3-diacylglycerols and free acidity indicating that glycerol is the final product of the partial hydrolysis of triacylglycerols.

  • Determination of Glycerol in Wines Using ^31PNMR Spectroscopy
    Journal of the American Oil Chemists' Society, 2007
    Co-Authors: Emanuel 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.

Claude Lecomte – One of the best experts on this subject based on the ideXlab platform.

H. El Alaoui El Abdallaoui – One of the best experts on this subject based on the ideXlab platform.

  • Crystal structure and solid state 31P NMR spectroscopy of triphenylphosphine oxide complex of zinc(II) tetrafluoroborate
    Polyhedron, 1992
    Co-Authors: H. El Alaoui El Abdallaoui, Patrice Rubini, P. Tekely, D. Bayeul, Claude Lecomte
    Abstract:

    Abstract The crystal structure of Zn(TPPO)·2BF4 (TPPO = triphenyl phosphine oxide) has been determined by single-crystal X-ray diffraction: the zinc atom coordination polyhedron is a slightly distorted tetrahedron (Zn O) 12 = 1.905A, (O Zn O) = 109.5°); three Zn O P angles are equal (Zn O P) = 150.3°), whereas due to steric constraints the fourth angle equals 170.1°. The observation of four signals in the 31P NMR Spectrum of the complex in the solid state is in agreement with this crystal structure.

Françoise M. Winnik – One of the best experts on this subject based on the ideXlab platform.

B. D. Nageswara Rao – One of the best experts on this subject based on the ideXlab platform.

  • Changes in the 31P NMR Spectrum of rabbit muscle myosin subfragment 1. MgADP with temperature.
    Archives of Biochemistry and Biophysics, 2002
    Co-Authors: Bruce D. Ray, Mikhail I. Khoroshev, Manuel F. Morales, B. D. Nageswara Rao
    Abstract:

    In pioneering studies on the 31P NMR spectra of MgADP bound to the “molecular motormyosin subfragment 1 (S1) in the temperature range of 0 to 25 degrees C, Shriver and Sykes [Biochemistry 20 (1981) 2004-2012/6357-6362; Biochemistry 21 (1982) 3022-3028], proposed that MgADP binds to myosin S1 as a mixture of two interconvertible conformers with different chemical shifts for the beta-P resonance of the S1-bound MgADP and that the concentrations of these conformers are related by an equilibrium constant K(T). Their model implied that the weighted average of the chemical shifts of the beta-P(MgADP) for S1-bound MgADP asymptotically approaches a high temperature limit. Here, and in our earlier paper [K. Konno, K. Ue, M. Khoroshev, H., Martinez, B.D. Ray, M.F. Morales, Proc. Natl. Acad. Sci. USA 97 (2000) 1461-1466], we report experimental similarities to Shriver and Sykes, but diverge from them (especially at 0 degrees C) in not finding two distinct peaks and in finding that the average chemical shift does not change with temperature. Our observations can be explained by chemical exchange of beta-P(MgADP) of S1-bound MgADP between two nearly energetically equivalent environments.