Biomedical subjects

Bernard Quéméner

Publications and source records attributed to Bernard Quéméner.

10 recordsLinked to original sources

PubMed2007

Fast data preprocessing for chromatographic fingerprints of tomato cell wall polysaccharides using chemometric methods.

The variability in the chemistry of cell wall polysaccharides in pericarp tissue of red-ripe tomato fruit (Solanum lycopersicon Mill.) was characterized by chemical methods and enzymatic degradations coupled to high performance anion exchange chromatography (HPAEC) and mass spectrometry analysis. Large fruited line, Levovil (LEV) carrying introgressed chromosome fragments from a cherry tomato line Cervil (CER) on chromosomes 4 (LC4), 9 (LC9), or on chromosomes 1, 2, 4 and 9 (LCX) and containing quantitative trait loci (QTLs) for texture traits, was studied. In order to differentiate cell wall polysaccharide modifications in the tomato fruit collection by multivariate analysis, chromatograms were corrected for baseline drift and shift of the component elution time using an approach derived from image analysis and mathematical morphology. The baseline was first corrected by using a "moving window" approach while the peak-matching method developed was based upon location of peaks as local maxima within a window of a definite size. The fast chromatographic data preprocessing proposed was a prerequisite for the different chemometric treatments, such as variance and principal component analysis applied herein to the analysis. Applied to the tomato collection, the combined enzymatic degradations and HPAEC analyses revealed that the firm LCX and CER genotypes showed a higher proportion of glucuronoxylans and pectic arabinan side chains while the mealy LC9 genotype demonstrated the highest content of pectic galactan side chains. QTLs on tomato chromosomes 1, 2, 4 and 9 contain important genes controlling glucuronoxylan and pectic neutral side chains biosynthesis and/or metabolism.

Acetic Acid↗

PubMed2006

Structural characterization of underivatized arabino-xylo-oligosaccharides by negative-ion electrospray mass spectrometry.

Various arabino-xylo-oligosaccharides with known substitution patterns were assessed by negative ESI-Q-TOFMS and ESI-ITMS. The CID spectra of linear xylo-oligosaccharides and of nine isomeric mono- and disubstituted arabino-xylo-oligosaccharides established that structures differing in their substitution pattern can be differentiated by this approach. The negative-ion fragmentation spectra of the deprotonated quasi-molecular ions are mainly characterized by glycosidic cleavage ions from the C-series, which provide sequence informations, and by cross-ring cleavage (0,2)A(i) ions, which provide partial linkage information. When the collision energy increased, the cross-ring cleavage (0,2)A(i) ions underwent consecutive loss of water to produce (0,2)A(i)-18 fragment ions and glycosidic cleavage ions of the B-series are also produced besides the C(i) ions. Contrary to linear xylo-oligosaccharides, C(i) ions, which originate from C-3 monosubstituted xylosyl residues never produce the related cross-ring cleavage (0,2)A(i) ions. Disubstitution at O-2 and O-3 of xylosyl residues appears to enhance the production of the (0,2)A(i) ions compared to monosubstitution. For the differentiation of the mono- and disubstitution patterns of the penultimate xylosyl residue, the relative abundance of the glycosidic cleavage ions at m/z 263 and 299 found on Q-TOF CID spectra plays a relevant role and appears to be more informative than MS(n) spectra obtained on a ion trap instrument.

Arabinose↗

PubMed2005

Sugar beet (Beta vulgaris) pectins are covalently cross-linked through diferulic bridges in the cell wall.

Arabinan and galactan side chains of sugar beet pectins are esterified by ferulic acid residues that can undergo in vivo oxidative reactions to form dehydrodiferulates. After acid and enzymatic degradation of sugar beet cell walls and fractionation of the solubilized products by hydrophobic interaction chromatography, three dehydrodiferulate-rich fractions were isolated. The structural identification of the different compounds present in these fractions was performed by electrospray-ion trap-mass spectrometry (before and after (18)O labeling) and high-performance anion-exchange chromatography. Several compounds contained solely Ara (terminal or alpha-1-->5-linked-dimer) and dehydrodiferulate. The location of the dehydrodiferulate was assigned in some cases to the O-2 and in others to the O-5 of non-reducing Ara residues. One compound contained Gal (beta-1-->4-linked-dimer), Ara (alpha-1-->5-linked-dimer) and dehydrodiferulate. The location of the dehydrodiferulate was unambiguously assigned to the O-2 of the non-reducing Ara residue and O-6 of the non-reducing Gal residue. These results provide direct evidence that pectic arabinans and galactans are covalently cross-linked (intra- or inter-molecularly) through dehydrodiferulates in sugar beet cell walls. Molecular modeling was used to compute and structurally characterize the low energy conformations of the isolated compounds. Interestingly, the conformations of the dehydrodiferulate-bridged arabinan and galactan fragments selected from an energetic criterion, evidenced very nice agreement with the experimental occurrence of the dehydrodiferulated pectins. The present work combines for the first time intensive mass spectrometry data and molecular modeling to give structural relevance of a molecular cohesion between rhamnogalacturonan fragments.

Beta vulgaris↗

PubMed2005

Resolution of the structural isomers of partially methylesterified oligogalacturonides by polysaccharide analysis using carbohydrate gel electrophoresis.

Pectins differing in their degree and pattern of methylesterification are important in diverse aspects of plant physiology and also in many industrial applications. Determination of methylesterification fine structure and knowledge of enzyme specificities in modification and fragmentation of pectin are key to understanding the relationship between structure and function. The development of methodologies for the detection, separation and sequencing of different partially methylesterified oligogalacturonides (Me-OGAs) is consequently very important. Polysaccharide analysis using carbohydrate gel electrophoresis (PACE) has been shown to be powerful for the quantitative resolution of species different in degree of polymerization (DP) and/or degree of methylesterification (DM). Mass spectrometry (MS) has, to date, been the only tool with which to obtain isomeric information. However, it is not quantitative, and the presence of isobaric species makes the interpretation of the fragmentation patterns complicated. Here, we present evidence that Me-OGAs with the same DP and DM but different patterns of methylesterification (structural isomers) can easily be separated and quantified using PACE.

Carbohydrate Conformation↗

PubMed2005

Mapping sugar beet pectin acetylation pattern.

Homogalacturonan-derived partly methylated and/or acetylated oligogalacturonates were recovered after enzymatic hydrolysis (endo-polygalacturonase+pectin methyl esterase+side-chain degrading enzymes) of sugar beet pectin followed by anion-exchange and size exclusion chromatography. Around 90% of the GalA and 75% of the acetyl groups present in the initial sugar beet pectin were recovered as homogalacturonan-derived oligogalacturonates, the remaining GalA and acetyl belonging to rhamnogalacturonic regions. Around 50% of the acetyl groups present in sugar beet homogalacturonans were recovered as partly methylated and/or acetylated oligogalacturonates of degree of polymerisation 5 whose structures were determined by electrospray ionization ion trap mass spectrometry (ESI-IT-MSn). 2-O-acetyl- and 3-O-acetyl-GalA were detected in roughly similar amounts but 2,3-di-O-acetylation was absent. Methyl-esterified GalA residues occurred mainly upstream 2-O-acetyl GalA. Oligogalacturonates containing GalA residues that are at once methyl- and acetyl-esterified were recovered in very limited amounts. A tentative mapping of the distribution of acetyl and methyl esters within sugar beet homogalacturonans is proposed. Unsubstituted GalA residues are likely to be present in limited amounts (approximately 10% of total GalA residues), due to the fact that methyl and acetyl groups are assumed to be most often not carried by the same residues.

Acetylation↗

PubMed2004

Isolation of diferulic bridges ester-linked to arabinan in sugar beet cell walls.

After degradation of sugar beet cell walls with Driselase and fractionation of the solubilised products by hydrophobic interaction chromatography, a dehydrodiferuloylated oligoarabinan was isolated. Its structure was assigned to two dimers of (1-->5)-linked arabinose units esterified by a central 8-O-4' ferulic dimer. These results provide the first direct evidence that pectic arabinans in sugar beet cell walls may be covalently cross-linked through dehydrodiferulates.

Beta vulgaris↗

PubMed2004

Evidence for linkage position determination in known feruloylated mono- and disaccharides using electrospray ion trap mass spectrometry.

Various feruloylated arabinose- and galactose-containing mono- and disaccharides with known linkage configurations (2-O-(trans-feruloyl)-L-arabinopyranose, 5-O-(trans-feruloyl)-L-arabinofuranose, O-[2-O-(trans-feruloyl)-alpha-L-arabinofuranosyl]-(1-->5)-L-arabinofuranose, and O-[6-O-(trans-feruloyl)-beta-D-galactopyranosyl]-(1-->4)-D-galactopyranose) were analyzed by electrospray ionization mass spectrometry using an ion trap or a quadrupole time-of-flight (Q-TOF) mass analyzer. Collision-induced dissociation (CID) experiments using the two mass analyzers generated similar tandem mass spectrometric (MS/MS) fragmentation patterns. However, the ester-bond cleavage ions were more abundant using the Q-TOF mass analyzer. Compared with the positive ion mode, the negative ion mode produces simpler and more useful CID product-ion patterns. For arabinose-containing feruloylated compounds, results obtained with both analyzers show that it is possible to assign the location of the feruloyl group to the O-2 or O-5 of arabinosyl residues. In the characterization of the 2-O-feruloyl and 5-O-feruloyl linkages, the relative abundance of the cross-ring fragment ions at m/z 265 (-60 u or -62 u after 18O-labelling) and at m/z 217 (-108 u or -110 u after 18O-labelling) play a relevant role. For galactose-containing feruloylated compounds, losses of 60, 90 and 120 Da observed in MS3 experiment correspond to the production of 0,2A1, 0,3A1 and (0,2A1-60 Da) cross-ring cleavage ions, respectively, fixing the location of feruloyl group at the O-6 of the galactose residue.

Arabinose↗

PubMed2003

Structural characterization by both positive and negative electrospray ion trap mass spectrometry of oligogalacturonates purified by high-performance anion-exchange chromatography.

The off-line coupling of high-performance anion-exchange chromatography to electrospray ion trap mass spectrometry (ESI-IT-MS) is described. Two sets of isocratic conditions were optimised for the semi-preparative purification of oligogalacturonates of degree of polymerisation from 4 to 6 by monitoring eluates with either pulsed amperometric detection or evaporative light scattering detection in the presence of an online Dionex Carbohydrate Membrane Desalter (CMD). In these conditions, purified oligogalacturonate solutions were suitable, without further desalting steps, for infusion ESI-IT-MS experiments. This paper provides some interesting features of positive and negative ESI-IT-multiple MS (MSn) of these acidic oligosaccharides. The spectra acquired in both ion modes show characteristic fragments resulting from glycosidic bond and cross-ring cleavages. Under negative ionization conditions, the fragmentation of the singly-charged [M-H]- ions, as well as the Ci-, and Zi-, fragment ions through sequential MSn experiments, was always dominated by product ions from C- and Z-type glycosidic cleavages. All spectra also displayed 0.2 A-type cross-ring cleavage ions which carry linkage information. Collision-induced dissociation (CID) spectra of sodium-cationized species obtained under positive ionization conditions were more complex. Successive MSn experiments also led to the 0.2 A-type cross-ring cleavage ions observed together with B- and Y-type ions. The presence of the 0.2 A ion series was related to Mr 60 (C2H4O2) losses. Combined with the absence of the Mr 30 (CH2O) and the Mr 90 (C3H6O3) ions, these ions were indicative of 1-4 type glycosidic linkage.

Chromatography, High Pressure Liquid↗

PubMed2003

Assignment of acetyl groups to O-2 and/or O-3 of pectic oligogalacturonides using negative electrospray ionization ion trap mass spectrometry.

Partially acetylated and methylated oligogalacturonides produced by enzymatic hydrolysis of sugar beet pectin were analysed by negative electrospray ionization ion trap mass spectrometry (ESI-ITMS). The (18)O labelling of the oligomer reducing end allowed the precise assignment of the fragments resulting from glycosidic bond and cross-ring cleavages. The collisional-induced dissociation of the C(i) and Z(j) fragment ions through sequential MS(n) experiments always displayed (0, 2)A-type cross-ring cleavage ions which were related to C(2)H(4)O(2) losses. These (0, 2)A ions appeared to be highly diagnostic ions allowing the precise location of the acetyl groups to the O-2 and/or O-3 of the acetylated galacturonic acid residues.

Acetylation↗

PubMed2003

Structural characterisation by both positive- and negative-ion electrospray mass spectrometry of partially methyl-esterified oligogalacturonides purified by semi-preparative high-performance anion-exchange chromatography.

The off-line coupling of high-performance anion-exchange chromatography (HPAEC) to electrospray ionisation/ion trap mass spectrometry (ESI-ITMS) is described. The Dionex carbohydrate membrane desalter (CMD) has been assessed as an on-line chromatographic desalting system to remove the high sodium concentration necessary for the HPAEC separation of partially methyl-esterified oligogalacturonides. The developed HPAEC configuration proved to be suitable for indirect coupling with ESI-ITMS. This paper provides some interesting features of positive- and negative-ion multistage tandem mass spectrometry (MS(n)) analysis of these acidic oligosaccharides. The spectra acquired in both negative- and positive-ion modes show characteristic fragment ions resulting from glycosidic bond and cross-ring cleavages. Some new mass spectrometric fragmentation routes are also described. The positive-ion mode gave more complex spectra but was as informative as the negative-ion mode. ESI-ITMS was revealed to be, as previously reported from direct use on an unseparated enzymatic digest, a powerful sequencing technique for the determination of linkage type and the methyl ester distribution of partially methyl-esterified oligogalacturonides. Moreover, unlike matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-ToF MS), it gives valuable information on the elution behaviour of these oligomers in relation to their structure, namely the HPAEC co-elution of isomeric structures.

Chromatography, Ion Exchange↗