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181.
Marion Devaux Jaleh Ghashghaie Didier Bert Catherine Lambrot Arthur Gessler Camille Bathellier Jérôme Ogee Denis Loustau 《Rapid communications in mass spectrometry : RCM》2009,23(16):2511-2518
The study presents a comparison of two phloem sugar extraction methods. The amount of phloem sugar extracted and the carbon isotope composition (δ13C) of the total extracts and of the main phloem compounds separated by high‐performance liquid chromatography (sucrose, glucose, fructose and pinitol) are compared. These two phloem sap extraction methods are exudation in distilled water and a new method using centrifugation, which avoids the addition of any solvent. We applied both extraction methods on phloem discs sampled from 38‐year‐old Pinus pinaster trees in south‐western France throughout the period from June 2007 to December 2008 on different time‐scales: hourly, daily and monthly. We found that the centrifugation method systematically extracted ca. 50% less compounds from the phloem discs than the exudation method. In addition, the two extraction methods provided similar δ13C values of the total extracts, but the values obtained by the exudation method were 0.6‰ more negative than those calculated from the mass balance using the individual constituents. Over the growing season, both extraction methods exhibited lower total sugar content and more 13C‐enriched phloem sap in summer compared with winter values. These findings suggest that both extraction methods can be applied to study the carbon isotope composition of phloem sap, and the centrifugation method has the advantage that no solvent has to be added. The exudation method, however, is more appropriate for the quantification of the amounts of phloem sugars. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Denis J.‐Y. Marion Gaspard Huber Dr. Patrick Berthault Dr. Hervé Desvaux Prof. 《Chemphyschem》2008,9(10):1395-1401
We report a new phenomenon observed when the magnetization of dissolved hyperpolarized 129Xe is intense and opposite to the Boltzmann magnetization. Without radio‐frequency (rf) excitation, the system spontaneously emits a series of rf bursts characterized by very narrow bandwidths (0.03 Hz at 138 MHz). This chaotic NMR‐maser illustrates the increase in the complexity of spin dynamics at high magnetization levels by unveiling an inhomogeneous spatial organization of the xenon magnetization and an apparent dependence of the xenon transverse relaxation time on its polarization and/or on time. 相似文献
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J. P. Marion F. Müggler-Chavan R. Viani J. Bricout D. Reymond R. H. Egli 《Helvetica chimica acta》1967,50(6):1509-1516
A gas-chromatographic separation of cocoa aroma, followed by infra-red and mass-spectrometric identification, has yielded, besides 22 of the 91 previously described constituents, 35 new substances (8 aliphatic, 1 alicyclic, 7 aromatic, 9 o-heterocyclic, 4 pyrrolic, and 6 pyrazinic). 相似文献