Gilles Hayne, Biagio Marini et le duc de Neuburg

International audienceLe duc de Neuburg a été un mécène de choix durant la première moitié du XVIIe siècle. Dans son entourage ont évolué des musiciens de plus ou moins grande réputation. Une correspondance entre le duc et un de ces musiciens, Gilles Hayne révèle la face cachée de ce mécénat et met en scène un virtuose au talent incontestable et à la personnalité complexe : Biagio Marin

Establishing the occurrence of major and minorglucosinolates in Brassicaceae by LC-ESI-hybrid linearion-trap and Fourier-transform ion cyclotron resonancemass spectrometry

Glucosinolates (GLSs) are sulfur-rich plant secondary metabolites which occur in a variety of cruciferous vegetables and among various classes of them, genus Brassica exhibits a rich family of these phytochemicals at high, medium and low abundances. Liquid chromatography (LC) with electrospray ionization in negative ion mode (ESI-) coupled to a hybrid quadrupole lineariontrap (LTQ) and Fouriertransformioncyclotronresonancemass spectrometer (FTICRMS) was employed for the selective and sensitive determination of intact GLSs in crude sample extracts of broccoli (Brassica oleracea L. Var. italica), cauliflower (B. oleracea L. Var. Botrytis) and rocket salad (Eruca sativa L.) with a wide range of contents. When LTQ and FTICR mass analyzers are compared, the magnitude of the limit of detection was ca. 5/6-fold lower with the FTICR MS. In addition, the separation and detection by LC–ESI-FTICR MS provides a highly selective assay platform for unambiguous identification of GLSs, which can be extended to lower abundance (minor) GLSs without significant interferences of other compounds in the sample extracts. The analysis of Brassicaceae species emphasized the presence of eight minor GLSs, viz. 1-methylpropyl-GLS, 2-methylpropyl-GLS, 2-methylbutyl-GLS, 3-methylbutyl-GLS, n-pentyl-GLS, 3-methylpentyl-GLS, 4-methylpentyl-GLS and n-hexyl-GLS. The occurrence of these GLSs belonging to the saturated aliphatic side chain families C4, C5 and C6, presumably formed by chain elongation of leucine, homoleucine and dihomoleucine as primary amino acid precursors, is described. Based on their retention behavior and tandem MS spectra, all these minor compounds occurring in plant extracts of B. oleracea L. Var. italica, B. oleracea L. Var. Botrytis and E. sativa L. were tentatively identified

GRAPHICAL RESOLUTION OF HUMIC STRUCTURES

Advanced techniques have been recently used to obtain information on Natural Organic Matter (NOM). However, the current knowledge of the chemical structure of humic substances (HS) is still incomplete. These substances appear to be too complex mixtures of charged organic molecules, and their characterization remains one of the most stimulating challenges in modern environmental science. Knowledge of the chemical composition of NOM is of great importance for the definition of soil and water properties because it has a significant impact on the understanding of numerous molecular and global-scale processes. This study aims to apply two-dimensional graphical methods to resolve homologous series in mass spectra of humic extracts (Suwannee River, Nordic Aquatic, and Soil) obtained using FT-ICR / MS (Thermo LTQ FT, 7 Tesla) in negative ionization mode. Electrospray ionization (ESI) coupled with ultra-high resolution mass spectrometry offered by Fourier transformed ion cyclotron resonance (FT-ICR / MS) has emerged with great promise as it can provide an overview of the NOM composition and details on a molecular scale. NOM's very high-resolution FT-ICR spectra can be extremely complicated. These spectra usually contain many peaks at each nominal mass and thousands of peaks across the entire spectrum. Each peak can represent a chemically distinct compound. This complexity poses an analytical challenge to the study of spectra for structural interpretation. Two-dimensional graphing methods, such as Kendrick and van Krevelen graphs, have been successfully applied to very high-resolution mass spectra, allowing peaks to be sorted into complicated spectra from their homologous relatives across the mass range. In van Krevelen plots, ionic signals corresponding to structural similarities between homologous series of compounds involved in the loss or gain of functional groups are found on straight lines. We identified many interesting homologous regions and compared the three humic standards with each other. Finally, we recognized the structural relationships of the homologous series obtained through Kendrick graphs. The results showed homologous series in the Suwannee River and Nordic Aquatic samples compared to the soil-extracted samples (soil-FA and soil-HA). In particular, homologous series signals related to methylation/demethylation, hydrogenation/dehydrogenation, hydration/dehydration and oxidation/reduction processes were lower in the soil-FA van Krevelen diagrams. On the contrary, the differences were not so evident in all the homologous series for the soil-HA samples