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Deuterated Water (deuterated + water)
Selected AbstractsHydraulic lift in a neotropical savannaFUNCTIONAL ECOLOGY, Issue 5 2003M. Z. Moreira Summary 1We report hydraulic lift in the savanna vegetation of central Brazil (Cerrado). Both heat-pulse measurements and isotopic (deuterium) labelling were used to determine whether hydraulic lift occurred in two common species, and whether neighbouring small shrubs and trees were utilizing this water. 2Both techniques showed water uptake by tap-roots and reverse flow of water in lateral roots. Roots transferred hydraulically lifted water to the soil, and small shrubs and trees neighbouring the labelled individuals were labelled by deuterated water. 3Isotopic mass-balance equations and sap-flow measurements showed that water taken up by the central tap-root in each individual constituted only a small percentage of total flux of water through the treated plants. Mass-balance equations also indicated that small shrubs and trees neighbouring the treated plants utilized only a few thousandths of a per cent of the label. 4The small proportion of water uptake by the tap-root of these two species may be limiting hydraulic lift in this system, unless sinker roots descending from lateral roots contribute to hydraulic lift. [source] Liquid chromatography coupled to nuclear magnetic resonance spectroscopy for the identification of isoflavone glucoside malonates in T. pratense L. leaves.JOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2004Eva de Rijke Abstract Previous studies revealed that the main isoflavones in extracts of leaves of T. pratense L. are biochanin A and formononetin, their 7- O -glucosides, and two glucoside malonate isomers of each of them. Since LC,MS(/MS) did not provide sufficient information to distinguish the glucoside malonate isomers, in the present paper LC,NMR as well as off-line two-dimensional NMR were used to obtain further structural information. Matrix solid-phase dispersion (MSPD) was applied to obtain sufficiently high analyte concentrations to perform LC,NMR. Stop-flow reversed-phase LC,NMR was performed using a gradient of deuterated water and deuterated acetonitrile. Off-line COSY and NOESY experiments were carried out to determine the positions of the glucose moiety on the flavonoid aglycone, and of the malonate moiety on the glucose. Based on the fragmentation patterns in MS/MS and the NMR spectra, the two formononetin glucoside malonate isomers were identified as 7- O -,-D-glucoside 6““- O -malonate and 7- O -,-D-glucoside 4““- O -malonate; i.e. they only differ in the substitution position of the malonate group on the glucoside ring. The biochanin A glucoside malonate isomers, however, have quite different structures. The main and later eluting isomer is biochanin A 7- O -,-D-glucoside 6““- O -malonate, and the minor and earlier eluting isomer is 5-hydroxy-7-methoxyisoflavone 4“- O -,-D-glucoside 4““- O -malonate: the positions of the methoxy group and the glucoside 6““- O -malonate group on the flavonoid skeleton are interchanged. [source] Reorientational dynamics of p -sulfonatocalix[4]arene and of its La(III) complex in waterMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2004Yaėl Israėli Abstract The reorientational dynamics of p -sulfonatocalix[4]arene and of its La(III) complex in deuterated water were studied by 1H NMR longitudinal relaxation rates. It is shown that the relaxation is purely dipolar in the non-extreme narrowing regime. The distance between the geminal protons could be determined from the NMR data, giving good agreement with the values generally used in correlation time calculations. The correlation times show an Arrhenius behaviour in good agreement with previously reported data from 13C measurements for a similar uncomplexed calixarene. The Arrhenius energies of activation are identical for the uncomplexed and the complexed calixarenes, suggesting a reorientational motion strongly dependent on the structure of the water cage around the complex. This is also in agreement with a complexation of the La(III) cation in the second sphere of solvation of the sulfonate groups, as shown by molecular dynamics simulations. Copyright © 2004 John Wiley & Sons, Ltd. [source] Identification of isomeric tropane alkaloids from Schizanthus grahamii by HPLC-NMR with loop storage and HPLC-UV-MS/SPE-NMR using a cryogenic flow probePHYTOCHEMICAL ANALYSIS, Issue 2 2006Stefan Bieri Abstract Two fully automated HPLC-NMR methods are reported and compared for the structure elucidation of four isomeric tropane alkaloids from the stem-bark of an endemic Chilean plant, Schizanthus grahamii Gill. (Solanaceae). The first approach interfaced a conventional HPLC column to NMR by means of a loop storage unit. After elution with a mobile phase consisting of deuterated water and standard protonated organic solvents, the separated analytes were momentarily stored in a loop cassette and then transferred one-at-a-time to the NMR flow probe for measurements. The second strategy combined HPLC with parallel ion-trap MS detection and NMR spectroscopy using an integrated solid-phase extraction (SPE) unit for post-column analyte trapping. The SPE cartridges were dried under a gentle stream of nitrogen and analytes were sequentially eluted and directed to a cryogenically cooled flow-probe with an NMR-friendly solvent. The structures of the four isomeric alkaloids, 3, -senecioyloxy-7, -hydroxytropane, 3, -hydroxy-7, -angeloyloxytropane, 3, -hydroxy-7, -tigloyloxytropane and 3, -hydroxy-7, -senecioyloxytropane, were unambiguously determined by combining NMR assignments with MS data. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||