Publications (19)50.61 Total impact
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Article: Tandem mass spectrometry of low solubility Polyamides
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ABSTRACT: The structural characterization of Polyamides (PA) was achieved by tandem mass spectrometry (MS/MS) with a Laser Induced Dissociation (LID) strategy. Because of interferences for precursor ions selection, two chemical modifications of the polymer end groups were proposed as derivatization strategies. The first approach, based on the addition of a trifluoroacetic acid (TFA) molecule, yields principally to complementary bn and yn product ions. This fragmentation types, analogous to those obtained with peptides or other PA, give only poor characterization of polymer end-groups.[1] A second approach, based on the addition of a basic diethylamine (DEA), permits to fix the charge and favourably direct the fragmentation. In this case, bn ions were not observed. The full characterization of ω end group structure was obtained, in addition to the expected yn and consecutive fragment ions.Analytica Chimica Acta 04/2013; · 4.55 Impact Factor -
Article: Off-line capillary electrophoresis/matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry for analysis of synthesized poly(amido)amine dendrimers.
Rapid Communications in Mass Spectrometry 08/2012; 26(15):1718-24. · 2.79 Impact Factor -
Article: Solvent-based and solvent-free characterization of low solubility and low molecular weight polyamides by mass spectrometry: a complementary approach.
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ABSTRACT: Polyamides (PA) belong to the most used classes of polymers because of their attractive chemical and mechanical properties. In order to monitor original PA design, it is essential to develop analytical methods for the characterization of these compounds that are mostly insoluble in usual solvents. A low molecular weight polyamide (PA11), synthesized with a chain limiter, has been used as a model compound and characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). In the solvent-based approach, specific solvents for PA, i.e. trifluoroacetic acid (TFA) and hexafluoroisopropanol (HFIP), were tested. Solvent-based sample preparation methods, dried-droplet and thin layer, were optimized through the choice of matrix and salt. Solvent-based (thin layer) and solvent-free methods were then compared for this low solubility polymer. Ultra-high-performance liquid chromatography/electrospray ionization (UHPLC/ESI)-TOF-MS analyses were then used to confirm elemental compositions through accurate mass measurement. Sodium iodide (NaI) and 2,5-dihydroxybenzoic acid (2,5-DHB) are, respectively, the best cationizing agent and matrix. The dried-droplet sample preparation method led to inhomogeneous deposits, but the thin-layer method could overcome this problem. Moreover, the solvent-free approach was the easiest and safest sample preparation method giving equivalent results to solvent-based methods. Linear as well as cyclic oligomers were observed. Although the PA molecular weights obtained by MALDI-TOF-MS were lower than those obtained by (1)H NMR and acido-basic titration, this technique allowed us to determine the presence of cyclic and linear species, not differentiated by the other techniques. TFA was shown to induce modification of linear oligomers that permitted cyclic and linear oligomers to be clearly highlighted in spectra. Optimal sample preparation conditions were determined for the MALDI-TOF-MS analysis of PA11, a model of polyamide analogues. The advantages of the solvent-free and solvent-based approaches were shown. Molecular weight determination using MALDI was discussed.Rapid Communications in Mass Spectrometry 06/2012; 26(11):1347-54. · 2.79 Impact Factor -
Article: Mechanistic study of maleic anhydride grafting onto fatty double bonds using mass spectrometry.
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ABSTRACT: The grafting of maleic anhydride onto fatty C=C double bonds is a well-known and used method to functionalize triglyceride molecules. Nevertheless, grafted products are not actually structurally well defined. In this work, the thermal grafting of maleic anhydride onto (un)saturated fatty acid esters without the use of an initiator was characterized in order to determine the nature of the products formed during this reaction. Complementary spectrometric techniques, ESI-MS(n) (ion-trap mass spectrometer), IMS-MS(n) (Q-IMS-TOFMS) and GC/MS, were used to identify the grafted products which were prepared using either ethyl oleate (EtO) or methyl linoleate (MeL) as model molecules and maleic anhydride (MA). Lithiated adducts were investigated since they yield useful structural information when subjected to collision-induced dissociation (CID) in tandem mass spectrometry. A high number of products are formed during MA grafting and various reaction types could occur. Radical addition of maleic anhydride followed by combination or elimination reactions led to succinic and maleic anhydride grafting, respectively. The addition occurred with or without double-bond shift; the resulting derivatives showed succinic and maleic anhydride branching in the α-position relative to the double bond or onto the carbon atom of the initial double bond. Some structures obtained by radical addition and combination were also consistent with the Alder ene functionalization reaction. The Diels-Alder addition between di-unsaturated fatty acid chains and maleic anhydride could yield cyclic forms of MA-grafted derivatives. We have shown that ESI-MS(n) and IMS-MS(n) allow the identification of grafted products providing relevant structural information concerning isomers. These methods permit the rapid and direct analyses of 'crude reaction mixtures'.Rapid Communications in Mass Spectrometry 06/2012; 26(11):1265-76. · 2.79 Impact Factor -
Article: Solvent-based and solvent-free characterization of low solubility and low molecular weight polyamides by mass spectrometry: a complementary approach
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ABSTRACT: RATIONALE: Polyamides (PA) belong to the most used classes of polymers because of their attractive chemical and mechanical properties. In order to monitor original PA design, it is essential to develop analytical methods for the characterization of these compounds that are mostly insoluble in usual solvents. METHODS: Alow molecularweight polyamide (PA11), synthesized with a chain limiter, has been used as amodel compound and characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). In the solvent-based approach, specific solvents for PA, i.e. trifluoroacetic acid (TFA) and hexafluoroisopropanol (HFIP), were tested. Solvent-based sample preparation methods, dried-droplet and thin layer, were optimized through the choice of matrix and salt. Solvent-based (thin layer) and solvent-free methods were then compared for this low solubility polymer. Ultra-high-performance liquid chromatography/electrospray ionization (UHPLC/ESI)-TOF-MS analyses were then used to confirm elemental compositions through accurate mass measurement. RESULTS: Sodium iodide (NaI) and 2,5-dihydroxybenzoic acid (2,5-DHB) are, respectively, the best cationizing agent and matrix. The dried-droplet sample preparation method led to inhomogeneous deposits, but the thin-layer method could overcome this problem. Moreover, the solvent-free approach was the easiest and safest sample preparation method giving equivalent results to solvent-based methods. Linear as well as cyclic oligomers were observed. Although the PA molecular weights obtained by MALDI-TOF-MS were lower than those obtained by 1H NMR and acido-basic titration, this technique allowed us to determine the presence of cyclic and linear species, not differentiated by the other techniques. TFA was shown to induce modification of linear oligomers that permitted cyclic and linear oligomers to be clearly highlighted in spectra. CONCLUSIONS: Optimal sample preparation conditions were determined for the MALDI-TOF-MS analysis of PA11, a model of polyamide analogues. The advantages of the solvent-free and solvent-based approaches were shown. Molecular weight determination using MALDI was discussed.Rapid Communications in Mass Spectrometry. 06/2012; 26(11-10.1002/rcm.6231):1347–1354. -
Article: Stand reaction of linseed oil
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ABSTRACT: Several theories have been proposed concerning the stand oil reaction but no precise reaction scheme has been described. In this work, the stand reaction of linseed oil was characterized in order to determine the nature of the products formed during this reaction. Using complementary analytical techniques (more especially NMR and mass spectrometry), the existence of two different reactions was demonstrated: the Diels–Alder addition between fatty acid chains and the addition of a methylene radical on double bonds, followed by combination or elimination reactions.European Journal of Lipid Science and Technology 01/2011; 113(5):616 - 626. · 1.73 Impact Factor -
Article: Contribution of two approaches using electrospray ionization with multi-stage mass spectrometry for the characterization of linseed oil.
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ABSTRACT: A detailed characterization of triacylglycerols (TAGs) present in linseed oil samples from a local producer was performed using electrospray ionization and two mass spectrometric approaches; direct infusion multi-stage mass spectrometry (MS(n)) experiments and liquid chromatography/tandem mass spectrometry (LC/MS/MS) using non-aqueous reversed-phase chromatographic conditions. The combination of both approaches permitted the identification of 26 TAGs. Comparison of the two analytical approaches showed that discrimination of regioisomers was achieved from MS3 data while other isobaric species were separated and identified by LC/MS/MS analysis. The results we obtained were also compared with those previously reported. The TAG composition of the studied linseed oil is qualitatively identical to that of linseed oils from various sources in Europe, Canada, Argentina or India. However, a few differences were observed with regard to the proportions of some TAGs; these can be explained by variations in the culture conditions, climate, and variety of the seeds.Rapid Communications in Mass Spectrometry 11/2009; 23(23):3743-52. · 2.79 Impact Factor -
Article: Photocrosslinking of a novel alpha,omega-unsaturated copolyamide: mass spectrometric study on model compounds with benzophenone as photoinitiator.
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ABSTRACT: The aim of this work was to understand the reactions involved in the photocrosslinking processes of a alpha,omega-unsaturated copolyamide foreseen as a new UV-curable powder coating. The crosslinking reaction was photoinitiated with benzophenone. In this paper, the photochemical reaction between benzophenone and several model compounds was investigated. The model compounds contained functional groups which could be present in copolyamide. The products resulting from UV curing were identified using a combination of high-resolution mass spectrometry and MS(n) experiments. The characterization of the products allowed localization of the hydrogen abstraction by the type II photoinitiator during UV curing and, consequently, the determination of the reactive sites of the unsaturated polyamide chain which were involved in the photochemical reaction.Rapid Communications in Mass Spectrometry 11/2009; 23(23):3813-23. · 2.79 Impact Factor -
Article: Erratum: Lipid composition of membranes of Escherichia coli by liquid chromatography/tandem mass spectrometry using negative electrospray ionisation.
Rapid Communications in Mass Spectrometry 10/2008; 22(20):3338. · 2.79 Impact Factor -
Article: Structural characterization of trimethylsilyl methyl glycosides derivatives by high-resolution mass spectrometry, linked scans and MIKE experiments.
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ABSTRACT: Gas chromatography-mass spectrometry investigations have been carried out for the structural analysis of trimethylsilyl methyl derivatives of keto-deoxy sugars and sialic acids studied under electron ionization. Fragmentation patterns were determined. The three derivatives undergo some common fragmentation pathways. Formation of fragment ions possessing cyclic resonance-stabilized structures was demonstrated. As the sialic acid derivative contained a N-acetyl substituent, some additional fragmentations occurred and were also elucidated. Thus, the mechanism of fragmentation was revealed for these derivatives and new findings concerning some series of fragment ions are presented.Analytical and Bioanalytical Chemistry 05/2008; 390(7):1853-60. · 3.78 Impact Factor -
Article: Identification and relative quantification of fatty acids in Escherichia coli membranes by gas chromatography/mass spectrometry.
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ABSTRACT: The lipids that are essential to the functioning of the bacterial membrane exist in hundreds of different forms. The reasons for this diversity are far from clear but are presumably related to the roles of these lipids in both facilitating enzymic activities and generating proteolipid domains. A full understanding of bacterial physiology therefore requires characterization of lipids in different strains in a variety of environmental conditions. This characterization then becomes the basis for lipidomics, the lipid aspect of the growing field of metabolomics. To exploit the power of derivatization chemistry and of gas chromatography/mass spectrometry (GC/MS) and tandem mass spectrometry (MS/MS) for metabolomics studies, we report here the development of various GC/MS electron ionization (EI) and negative and positive chemical ionization (CI) methods for the identification and, for the first time, the relative quantification of fatty acids present in extracts from membranes of a laboratory strain of Escherichia coli. They consist of seven saturated fatty acids (C10:0, C12:0, C14:0, C15:0, C16:0, C17:0 and C18:0) and six unsaturated fatty acids (C16:1, cyC17:0 plus two isomers of C18:1, C18:2 and cyC19:0).Rapid Communications in Mass Spectrometry 02/2007; 21(20):3229-33. · 2.79 Impact Factor -
Article: Lipid composition of membranes of Escherichia coli by liquid chromatography/tandem mass spectrometry using negative electrospray ionization.
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ABSTRACT: A liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method using reversed-phase chromatography was developed for the analysis of phospholipids from bacterial extracts of a wild-type strain of Escherichia coli. Product ion mass spectra from [M--H](-) precursor ions allowed an identification of individual phospholipid species that includes both fatty acid composition and fatty acyl location on the glycerol backbone using diagnostic product ions. Thus, complete assignment, including sn-1/sn-2 fatty acyl position, was achieved for this strain of E. coli. In addition, the phospholipids were quantified relative to one another using an internal standard method.Rapid Communications in Mass Spectrometry 02/2007; 21(11):1721-8. · 2.79 Impact Factor -
Article: Synthesis of new anionic HTPB‐based polyurethane elastomers: Aqueous dispersion and physical properties
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ABSTRACT: New segmented polyurethane (PU) anionomers based on hydroxytelechelic polybutadiene (HTPB) were synthesized via an environment-friendly chemical route. Incorporation of carboxylated functions on the PU soft segment was carried out using a thiol-ene reaction on HTPB vinyl double bonds with thioglycolic acid. PU water dispersions were obtained by addition of a water dispersible polyisocyanate, i.e., Bayhydur® 3100, to the modified ionic HTPB water dispersions. The key factor of this formulation is the control of ionic concentration apart from the hard segment content, oppositely to all other PU anionomer formulations. The influence of ionic content was studied through all steps of the PU material synthesis, from aqueous dispersions upto crosslinked materials' physical properties. For fully neutralized precursors, the stability of the ionic aqueous dispersions was higher than that was in six months. In all cases, particles were smaller than 200 nm. PU glass transition temperature, surface hydrophily and swelling increased with ionic content. But, however, PUs exhibit hydrophobic surface properties with a maximum surface tension of 45 mN m−1 and a limited water uptake. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3312–3322, 2006Journal of Applied Polymer Science 05/2006; 100(4):3312 - 3322. · 1.29 Impact Factor -
Article: Mutants in DEFECTIVE GLYCOSYLATION, an Arabidopsis homolog of an oligosaccharyltransferase complex subunit, show protein underglycosylation and defects in cell differentiation and growth.
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ABSTRACT: A mutant called defective glycosylation1-1 (dgl1-1) was identified in Arabidopsis based on a growth defect of the dark-grown hypocotyl and an abnormal composition of the non-cellulosic cell wall polysaccharides. dgl1-1 is altered in a protein ortholog of human OST48 or yeast WBP1, an essential protein subunit of the oligosaccharyltransferase (OST) complex, which is responsible for the transfer in the ER of the N-linked glycan precursor onto Asn residues of candidate proteins. Consistent with the known function of the OST complex in eukaryotes, the dgl1-1 mutation led to a reduced N-linked glycosylation of the ER-resident protein disulfide isomerase. A second more severe mutant (dgl1-2) was embryo-lethal. Microscopic analysis of dgl1-1 revealed developmental defects including reduced cell elongation and the collapse and differentiation defects of cells in the central cylinder. These defects were accompanied by changes in the non-cellulosic polysaccharide composition, including the accumulation of ectopic callose. Interestingly, in contrast to other dwarf mutants that are altered in early steps of the N-glycan processing, dgl1-1 did not exhibit a cellulose deficiency. Together, these results confirm the role of DGL1 in N-linked glycosylation, cell growth and differentiation in plants.The Plant Journal 06/2005; 42(4):455-68. · 6.16 Impact Factor -
Article: Protein N-glycosylation is similar in the moss Physcomitrella patens and in higher plants.
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ABSTRACT: We have investigated the structure of glycans N-linked to the proteins of the moss Physcomitrella patens. The structural elucidation was carried out by western blotting using antibodies specific for N-glycan epitopes and by analysis of N-linked glycans enzymatically released from a total protein extract by combination of MALDI-TOF and MALDI-PSD mass spectrometry analysis. Nineteen N-linked oligosaccharides were characterised ranging from high-mannose-type and truncated paucimannosidic-type to complex-type N-glycans harbouring core-xylose, core-alpha(1,3)-fucose and Lewis(a), as previously described for proteins from higher plants. This demonstrates that the processing of N-linked glycans, as well as the specificity of glycosidases and glycosyltransferases involved in this processing, are highly conserved between P. patens and higher plants. As a consequence, P. patens appears to be a new promising model organism for the investigation of the biological significance of protein N-glycosylation in the plant kingdom, taking advantage of the potential for gene targeting in this moss.Planta 01/2004; 218(2):269-75. · 3.00 Impact Factor -
Article: Structural investigation of hemicellulosic polysaccharides from Argania spinosa: characterisation of a novel xyloglucan motif.
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ABSTRACT: Hemicellulose polymers were isolated from Argania spinosa leaf cell walls by sequential extractions with alkali. The structure of the two main polymers, xylan and xyloglucan, was investigated by enzyme degradation with specific endoglycosidases followed by analysis of the resulting fragments by high performance anion exchange chromatography (HPAEC) and matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-TOF MS). The results show that A. spinosa xylan is composed of a beta-(1-->4)-linked-D-xylopyranose backbone substituted with 4-O-methyl-D-glucuronic acid residues. Xyloglucan oligosaccharide subunits were generated by treatment with an endo-(1-->4)-beta-D-glucanase of the xyloglucan-rich hemicellulosic fractions. MALDI-TOF mass spectra and HPAE-PAD chromatography of the pool of endoglucanase-generated xyloglucan oligomers indicated that A. spinosa cell wall contains a XXXG-type xyloglucan. In addition to XXXG, XXFG, XLXG/XXLG, XLFG fragments previously characterised in various plants, a second group of XXXG-type fragments was detected. The primary structure of the major subunit was determined by a combination of sugar analysis, methylation analysis, post-source decay (PSD) fragment analysis of MALDI-TOF MS and 1H NMR spectroscopy. This fragment, termed XUFG, contains a novel beta-D-Xylp-(1-->2)-alpha-D-Xylp side chain linked to C-6 of the second glucose unit from the nonreducing end of the cellotetraose sequence.Carbohydrate Research 01/2004; 339(2):201-8. · 2.33 Impact Factor -
Article: Monoclonal C5-1 antibody produced in transgenic alfalfa plants exhibits a N-glycosylation that is homogenous and suitable for glyco-engineering into human-compatible structures.
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ABSTRACT: Structural analysis of the N-glycosylation of alfalfa proteins was investigated in order to evaluate the capacity of this plant to perform this biologically important post-translational modification. We show that, in alfalfa, N-linked glycans are processed into a large variety of mature oligosaccharides having core-xylose and core alpha(1,3)-fucose, as well as terminal Lewis(a) epitopes. In contrast, expression of the C5-1 monoclonal antibody in alfalfa plants results in the production of plant-derived IgG1 which is N-glycosylated by a predominant glycan having a alpha(1,3)-fucose and a beta(1,2)-xylose attached to a GlcNAc2Man3GlcNAc2 core. Since this core is common to plant and mammal N-linked glycans, it therefore appears that alfalfa plants have the ability to produce recombinant IgG1 having a N-glycosylation that is suitable for in vitro or in vivo glycan remodelling into a human-compatible plantibody. For instance, as proof of concept, in vitro galactosylation of the alfalfa-derived C5-1 mAb resulted in a homogenous plantibody harbouring terminal beta(1,4)-galactose residues as observed in the mammalian IgG.Plant Biotechnology Journal 12/2003; 1(6):451-62. · 5.44 Impact Factor -
Article: Polysaccharides from Sesamum indicum meal: Isolation and structural features
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ABSTRACT: Defatted Sesamum indicum seed cake was extracted, following two separate sequences, and the effects of extraction medium on yield and composition of the extracts were compared. Polysaccharides extracted sequentially with dilute acid and alkali represented 250 mg/g of defatted meal. The isolated polymers contained arabinan, rhamnogalacturonan I (RG I) and arabinogalactan proteins. Polysaccharides extracted during chlorite treatment and with dilute alkali had a higher proportion of rhamnose, suggesting a more branched variety of polymer. Three extracts, which were further characterized by size exclusion chromatography, gave two overlapping peaks. Structural characterisation of hemicellulosic polysaccharides, isolated with KOH, using specific enzyme hydrolysis, ion exchange chromatography (HPAEC) and matrix assisted laser desorption ionisation-time-of-flight (MALDI-TOF) mass spectroscopy, showed that sesame meal xyloglucan (XG) contained XXXG, XXFG and XXLG, and XLLG (named according to Fry et al., 1993) as the major building sub-units in the ratio of 1:0.9:0.3. Hydrolysis with endo-β-(1 → 4)-d-xylanase and analysis of the xylan derived oligosaccharides showed the presence of monomeric xylose (40%), xylobiose (46%) and acidic xylan oligosaccharides containing 4-O-methyl-d-glucuronic acid residues (14%).Food Chemistry. -
Article: Analysis of plant glycoproteins by matrix-assisted laser desorption ionisation mass spectrometry: Application to the N-glycosylation analysis of bean phytohemagglutinin
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ABSTRACT: Matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) spectrometry is a recently developed soft ionisation mass spectrometry technique which appears as a highly efficient tool for the N-glycosylation analysis of glycoproteins. The potentiality of this analytical technique is illustrated through the analysis of the N-glycosylation of the isolectin L of bean phytohemagglutinin (PHA-L). The analysis was carried out on the native PHA-L as well as on the N-glycans released from this lectin. Furthermore, the two glycopeptides containing the potential N-glycosylation sites prepared by proteolytic cleavage of PHA-L and purified by HPLC were analysed by MALDI-TOF. This study has confirmed that PHA-L is N-glycosylated by two populations of oligosaccharides, high-mannose-type N-glycans and paucimannosidic-type N-glycans, located on Asn-12 and Asn-60, respectively, and has pointed out the microheterogeneity of the glycans N-linked on both Asn residues.Plant Physiology and Biochemistry.
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Institutions
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2004–2012
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Université de Rouen
Mont-Saint-Aignan, Haute-Normandie, France
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2003–2009
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French National Centre for Scientific Research
Lyon, Rhone-Alpes, France
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