References of "De Pauw, Edwin"
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See detailFirst evidence of the possible implication of the 11-deoxycorticosterone (DOC) in immune activity of Eurasian perch (Perca fluviatilis, L.): Comparison with cortisol
Mathieu, Cédric; Mila, Sylvain; Mandiki, Robert et al

in Comparative Biochemistry & Physiology Part A : Molecular & Integrative Physiology (2013), 165(2), 149-158

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See detailIon-Mobility mass spectrometry as a potential tool to assign disulfide bonds arrangements in peptides with multiple disulfide bridges.
Echterbille, Julien ULg; Quinton, Loïc ULg; Gilles, Nicolas et al

in Analytical Chemistry (2013)

Disulfide bridges play a major role in defining the structural properties of peptides and proteins. However, the determination of the cysteine pairing is still challenging. Peptide sequences are usually ... [more ▼]

Disulfide bridges play a major role in defining the structural properties of peptides and proteins. However, the determination of the cysteine pairing is still challenging. Peptide sequences are usually achieved using MS/MS spectra of the totally reduced unfolded species but the cysteine pairing information is lost. On the other hand, MS/MS experiments performed on native folded species show complex spectra composed of non-classical ions. MS/MS alone does not allow the cysteine pairing nor the full sequence of an unknown peptide to be determined. The major goal of this work is to set up a strategy for the full structural characterization of peptides including disulfide bridges annotation in the sequence. This strategy was developed by combining Ion Mobility Spectrometry (IMS)and Collision Induced Dissociation(CID). It is assumed that the opening of one S-S bridges in a peptide leads to a structural evolution which results in a modification of IMS drift time. In the presence of multiple S-S bridges, the shift in arrival time will depend on which disulfide(s) has (have) been reduced and on the shape adopted by the generated species. Due to specific fragmentations observed for each species, CID experiments performed after the mobility separation could provide not only information on peptide sequence, but also on the localization of the disulfide bridges. To achieve this goal, synthetic peptides containing two disulfides were studied. The openings of the bridges were carried out following different experimental conditions such as reduction, reduction/alkylation or oxidation. Due to disulfide scrambling highlighted with the reduction approaches, oxidation of S-S bonds into cysteic acids appeared to be the best strategy. Cysteines connectivity was then unambiguously determined for the two peptides, without any disulfide scrambling interference. [less ▲]

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See detailSéminaire des chercheurs Télévie 2013
Cimino, Jonathan ULg; Sounni, Nor Eddine ULg; Calligaris, David ULg et al

Poster (2012, December 10)

Séminaire des chercheurs Télévie 2013

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See detailSecretion and maturation of conotoxins in the venom ducts of Conus textile
Dobson, Rowan ULg; Collodoro, Mike; Gilles, Nicolas et al

in Toxicon (2012), 60(8), 1370-1379

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See detailUtilisation des termites comme source de microorganismes dans la filière de production du bioéthanol de seconde génération
Tarayre, Cédric ULg; Bauwens, Julien ULg; Brasseur, Catherine ULg et al

Poster (2012, November 14)

Les termites abritent une microflore symbiotique qui intervient dans la dégradation des fibres constitutives du bois, synthétisant des enzymes capables d’hydrolyser ses composants. Les sucres ... [more ▼]

Les termites abritent une microflore symbiotique qui intervient dans la dégradation des fibres constitutives du bois, synthétisant des enzymes capables d’hydrolyser ses composants. Les sucres fermentescibles libérés suite à cette hydrolyse sont utilisables dans le cadre de la production du bioéthanol de seconde génération. [less ▲]

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See detailNew Advances for In Situ Protein Identification by MALDI In-Source Decay FTMS Imaging
Calligaris, David; Longuespée, Rémi ULg; Zimmerman, Tyler et al

Poster (2012, November)

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See detailDetermination of the molecular players of adaptation to anti-angiogenic therapy in breast cancer by quantitative proteomic and high molecular MALDI Imaging.
Cimino, Jonathan ULg; Sounni, Nor Eddine ULg; Calligaris, David ULg et al

Poster (2012, October 13)

Breast carcinoma is the most common and second leading cause of cancer mortality in women. The recognition of the “angiogenic switch” as a rate-limiting secondary step in tumorigenesis led to extensive ... [more ▼]

Breast carcinoma is the most common and second leading cause of cancer mortality in women. The recognition of the “angiogenic switch” as a rate-limiting secondary step in tumorigenesis led to extensive pre-clinical researches on angiogenesis and finally the approval of VEGF-neutralizing antibodies (bevacizumab) and VEGF receptor tyrosine kinase inhibitors (RTKs:Sunitinib). The Sunitinib has been used clinically in patients with breast cancer refractory to other therapeutic agents. Unfortunately, like the cytotoxic therapies, these drugs do not produce lasting effects and resistance to treatment appeared clinically. Questions have emerged about the failure of anti-angiogenic therapy in clinic and the limitations of predictive preclinical models, and also about the molecular assessment of all stages of tumor adaptation and me<x>tastatic disease. To this end, we applied quantitative proteomics and imaging mass spectrometry tools to visualize and study the profiles of proteins and small molecules associated with tumor treated or not with Sunitinib using a novel preclinical model of breast carcinoma cells. In this project, we first developed a reproducible model of resistance to Sunitinib of human triple negative breast cancer MDA-MB-231 cells expressing luciferase gene. Cells were subcutaneously injected into mice RAG1-/- and divided into four experimental groups including, control mice treated with vehicle or Sunitinib for 30 days and sacrificed 1 days after treatment withdrawal or when tumor reached a volume of 300 mm3. In the second step. Tumors were analyzed using a nanoAcquity UPLC Synapt TM HDMS TM G1 (Waters, Manchester,UK) and Mass Spectrometry Imaging. For quantitative proteomic analyses of tumors, a bioinformatics analysis was used with the Protein lynx global server 2.2.5 software. Imaging mass spectrometry was performed on tissue sections of tumors and organs subsequently colonized by me<x>tastases. Matrix sublimation was used to coat tumor sections (14 µm-tick) with 1.5 Diaminonaphthalene for lipids analysis and Sinapinic acid for entire proteins analysis. Ion cartographies were recorded with a Solarix 9.4T FTMS instrument for lipids and with an Ultraflex II TOF-TOF instrument for entire proteins (Bruker Daltonics, Germany) with a spatial resolution of 100 µm. Global protemic revealed different protein profiles between tumor treated or not with Sunitinib. The Mass Spectrometry Imaging detected differences in intensity and location of some proteins and lipids are also associated with some histological features including inflammatory, necrotic and angiogenic areas. Bioinformatics analysis will be applied to ensure the integration of all data in order to provide the basis for identifying molecular pathways activated during the acquisition of refractoriness to drug treatments. [less ▲]

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See detailPotential of CE/MS for Small Carboxylic Acids Analysis as Alternative to GC/MS Reference Analytical Methods
Far, Johann ULg; Falmagne, Jean-Bernard, ANALIS R&D; de l'Escaille, François, ANALIS R&D et al

Poster (2012, October)

GC/MS (Gas Chromatography coupled to Mass Spectrometry) is the analytical method of choice for carboxylic acids analysis because of good sensitivity, low limit of detection and the possibility to compare ... [more ▼]

GC/MS (Gas Chromatography coupled to Mass Spectrometry) is the analytical method of choice for carboxylic acids analysis because of good sensitivity, low limit of detection and the possibility to compare the pattern of fragmentation with existing databases for identification. However GC requires that the analytes are volatile. If it is not the case, the use of chemicals in order to perform the derivatization is mandatory, this may induce analytical bias. CE (Capillary electrophoresis) is a technique of choice for ions separation without prior treatments. The method is fast and do not require highly technical skills. A UV detector is the most common detection method; however electrospray mass spectrometry detection is recently gaining interest, while it really helps for structural information of the detected compounds. In this poster, the preliminary results of CE/MS analysis of several carboxylic acids are presented. All carboxylic acids are analyzed without any sample pretreatment. These acids looked at are from the “Citric Acid Cycle” including pyruvate and some isotope labeled analogues but also glyoxylate, lactate, oxalate and tartrate. Moreover, the preliminary results of a sample preparation approach to remove phosphate salts are presented. Phosphate is a very common salt that is often used in biological buffers but prevents the derivatization of carboxylic acid for GC/MS analysis and reduces the reproducibility of results for both GC/MS and CE/MS analysis. [less ▲]

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See detailDevelopment of a quantitative approach to measure phospholipids in dried drops by Raman spectroscopy
Malherbe, Cédric ULg; Jadoul, Laure; Gilbert, Bernard ULg et al

Poster (2012, October)

We present here the results obtained during our tentative to analyse quantitatively dried drops of phospholipidic solutions by Raman spectroscopy. Drops of different solutions of phospholipid were deposed ... [more ▼]

We present here the results obtained during our tentative to analyse quantitatively dried drops of phospholipidic solutions by Raman spectroscopy. Drops of different solutions of phospholipid were deposed onto different material supports. The spots were then analyses by confocal Raman microspectroscopy. Experimental settings have been optimised and the analysis of the intensity profile of the Raman signal inside the spot allows the establishment of a calibration curve for the determination of the phospholipids amount within a 1 µL solution. [less ▲]

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See detailFuran formation upon degradation of carbohydrates in combination with proteins and lipids
Owczarek, Agnieszka; De Meulenaer, Bruno; Scholl, Georges ULg et al

Conference (2012, September 20)

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See detailIntraocular Lens Adsorbome: a Proteomic Study of Adsorbed Proteins onto Acrylic Materials and Its Implication in Secondary Cataract
Huang, Yi-Shiang ULg; Bertrand, Virginie ULg; Mazzucchelli, Gabriel ULg et al

Poster (2012, September 17)

The intraocular lens (IOL) is a polymer implant designed to replace the natural lens after cataract surgery. When the implant is introduced into the lens capsule, the polymer starts to interact with the ... [more ▼]

The intraocular lens (IOL) is a polymer implant designed to replace the natural lens after cataract surgery. When the implant is introduced into the lens capsule, the polymer starts to interact with the aqueous humour and the exchange of molecules between the solid and the liquid begins. The nature of exchange in water, ions, and biomolecules may result in several postoperative complications including glistening, calcification, and posterior capsular opacification. The posterior capsular opacification (PCO, also called “Secondary Cataract”) is raised from the over-growth of residual lens epithelial cells. The first step of the over-growth process of the cells is their adhesion to the deposited biomolecules, such as proteins involved in extra-cellular matrices. The purpose of this study is to identify the principal proteins adsorbed onto the acrylic polymers by mass spectrometry. The concept of adsorbome is to generate a list of adsorbed proteins to the hydrophilic and hydrophobic polymers, and then compare the difference to the original component of aqueous humour in order to see the affinity of individual protein to each material. Two kinds of hydrophilic and two kinds of hydrophobic acrylic polymers were tested for their adsorbomes by treating them with an aqueous humour analogue and the major adsorbed proteins were identified by mass spectrometry. Interestingly, the hydrophilic acrylic polymer shows a relative lower protein adsorption rate but shows a higher incidence of secondary cataract. This phenomenon implies the adsorbed proteins play a crucial role in progress of secondary cataract. [less ▲]

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See detailDistribution and identification of molecular interactions between tomato roots and bacterial biofilms
Debois, Delphine ULg; Jourdan, Emmanuel ULg; Ongena, Marc ULg et al

Conference (2012, September 05)

Some non pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in ... [more ▼]

Some non pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in soil (1). To initiate both phenomena leading to biocontrol activity, microorganisms use plant exudates to grow on roots and to produce in-situ active compounds. In Bacilli, cyclic lipopeptides of the surfactin, iturin and fengycin families represent important antibiotics involved in biocontrol (2). Recent studies in microbiology allowed a better understanding of plant microorganism interactions but few has been done at the molecular level. In this study, MALDI MS imaging has been used to study the nature of the secreted lipopeptide molecules, their relative quantity and their distribution in the root’s environment. Disinfected tomato seeds were first germinated at 28°C in sterile conditions for germination. Seedlings were then placed in Petri dish on ITO glass slide recovered with a thin layer of plant nutritive solution (Hoagland) containing 1,75% of agar and treated with freshly-grown cells of Bacillus amyloliquefaciens S499. Petri dishes were finally incubated vertically in phytotron at 28°C with a 16h photoperiod. Different root age / time of incubation were studied: 13 / 3; 13 / 7; 21 / 14 and 39 / 32. Control tomato root (without bacterial treatment) of the same ages were also analyzed (13 / 0; 21 / 0 and 42 / 0. For MALDI imaging experiments, the ITO slide was removed from the agar and dried in a dessiccator under vacuum. The matrix solution (α-cyano-hydroxycinnamic acid, 5mg/mL in ACN/0.2% TFA 70/30) was applied with an ImagePrep automated sprayer (Bruker Daltonics). An UltraFlex II TOF/TOF and a Solarix FT-ICR mass spectrometers were used to record molecular cartographies. The average mass spectra recorded around the tomato root (2-3 mm on both sides of the root) showed that lipopeptides were major compounds detected on the agar. The relative intensity of lipopeptides families varied with respect to the age of the root/biofilm system. In the 13/3 system, 3 homologues of surfactins were essentially detected (C13, C14 and C15), with very few iturins and fengycins. Their localizations were identical, whatever the considered homologue. Then the production of iturin and fengycin families increases in older systems (13/7 and 21/14) and a novel homologue of surfactin is detected (C12). Some variations in localizations within families may be observed (around the root or at the close vicinity of it in function of the considered homologue or alkali adduct). Then for the oldest system we studied, iturins and fengycins are not detected anymore and the localization of surfactins is less precise. In the 39/32 system, we also detected unknown compounds at 986.6, 1000.6, 1014.7 and 1028.7 m/z. The mass range of these compounds allied to the mass difference between two consecutive ion peaks let us think that these unknown compounds could be a new lipopeptide family. Investigations are in progress to identify these new secondary metabolites of Bacillus amyloliquefaciens. [less ▲]

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See detailAnalysis of the Biocompatibility of Different Intraocular Lens (IOL) Material Using Mass Spectrometry Tisssue Imaging
Bertrand, Virginie ULg; Debois, Delphine ULg; Calligaris, David ULg et al

Conference (2012, September 04)

The cataract corresponds to the total or partial opacification of the lens of the eye preventing the passage of the light. At present, the surgery is the only effective treatment to overcome the cataract ... [more ▼]

The cataract corresponds to the total or partial opacification of the lens of the eye preventing the passage of the light. At present, the surgery is the only effective treatment to overcome the cataract. The surgical intervention consists in removing the cloudy lens and to replace it by an artificial intraocular lens (IOL). The in vivo implantation of these synthetic lenses involves the evaluation of several factors as their physico-chemical properties, their capacities to interact with lens epithelial cells and proteins, as well as their biocompatibility. During a previous study, we demonstrated major differences concerning the tackiness (atomic force microscopy), the cellular adhesion and the protein adsorption of various polymer disks intended for the manufacturing of intraocular lenses. The aim of this work was to correlate a histological analysis to a mass spectrometry imaging analysis performed on the same sample. To estimate the biocompatibility of the biomaterials, an animal testing was realized in rabbits. The various polymers were implanted subcutaneously. After one month, the 2 cm x 3 cm pieces of rabbit skin and underlying muscle with a 2 cm thickness were removed, fixed with formaldehyde 10% during six days, treated for the paraffin inclusion and stored at room temperature until use. Slices of 5 µm thickness were performed using a microtome. Paraffin was removed and tissue sections were washed in graded ethanol baths. The slices were then stained with the hematoxylin and eosin dyes. The analysis of stained sections showed different histo-morphological features according to the implanted polymer. For MALDI MSI purposes, on tissue protein digestion was performed using trypsin (1) and the MALDI matrix (α-cyanohydroxycinnamic acid, 5 mg/mL in ACN/0.2% TFA 70:30) was deposited using an ImagePrep automated sprayer (Bruker Daltonics, Bremen, Germany). Experiments were carried out using an UltraFlex II TOF/TOF mass spectrometer (Bruker Daltonics, Bremen, Germany). MALDI imaging can show the detection of different proteomic profiles according to the tested biomaterials, which may be considered as biocompatibility markers. The MALDI images of these markers are then correlated with the histo-morphological profiles. Consequently, mass spectrometry imaging can become a powerful tool in the evaluation of the biocompatibility of artificial implants in biomedical application. [less ▲]

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See detailStudy  of  breast  cancer  adaptation  to  anti-­angiogenic  therapies  by   molecular  imaging  on  tissue  slides
Cimino, Jonathan ULg; Calligaris, David ULg; Debois, Delphine ULg et al

Conference (2012, September 04)

Breast   carcinoma   is   the   most   common   and   second   leading   cause   of   cancer   mortality   in   women1.   The   ␣␣␣␣␣␣␣␣␣␣␣␣ ␣␣␣ ␣␣␣␣ ␣␣␣␣␣␣␣␣␣␣␣␣ ␣␣␣␣␣␣␣␣ ␣␣␣ ␣␣ ␣␣␣␣-­‐limiting   ... [more ▼]

Breast   carcinoma   is   the   most   common   and   second   leading   cause   of   cancer   mortality   in   women1.   The   ␣␣␣␣␣␣␣␣␣␣␣␣ ␣␣␣ ␣␣␣␣ ␣␣␣␣␣␣␣␣␣␣␣␣ ␣␣␣␣␣␣␣␣ ␣␣␣ ␣␣ ␣␣␣␣-­‐limiting   secondary   step   in   tumorigenesis   led   to   extensive   pre-­‐clinical   researches   on   angiogenesis   and   finally   the   approval   of   VEGF-­‐neutralizing   antibodies   (bevacizumab)  and  VEGF  receptor  tyrosine  kinase  inhibitors  (RTKs:sunitinib).  The  Sunitinib  has  been  used   clinically   in   patients   with   breast   cancer   refractory   to   other   therapeutic   agents2.   Unfortunately,   like   the   cytotoxic   therapies,   these   drugs   do   not   produce   lasting   effects   and   resistance   to   treatment   appeared   clinically3.   Recently,   independent   laboratories   have   reported   experimental   data   demonstrating   that   anti-­‐ angiogenic   treatments   inhibit   tumor   growth,   but   also   stimulate   the   formation   of   lung   metastases   after   treatment   discontinuation4.   The   field   of   imaging   mass   spectrometry   provides   new   tools   to   visualize   and   study  the  profiles  of  proteins  and  small  molecules  associated  with  biomedical  problems5.   To  this  aim,  we  conducted  a  series  of  experiments  to  setup  a  reproductible  model  of  resistance  to  sunitinib.   The   cells   MDA-­‐MB-­‐231   triple   negative,   from   human   breast   cancer   and   expressing   luciferase   are   injected   subcutaneously  into  mice  RAG1-­‐/-­‐.  The  mice  were  divided  into  four  experimental  groups  including,  on  the   one  hand,  control  mice  treated  with  placebo  (Carboxymethyl  cellulose,  CMC)  sacrificed  on  day  30  (group  1)   or  when  the  tumor  reached  a  volume  of  300  mm3  (group  2).    On  the  other  hand,  Sunitinib-­‐treated  mice  (LC   Laboratories,   40mg/kg/day),   sacrificed   at   day   30   (group   3),   or   when   the   tumor   reached   a   volume   of   300   mm3  (group  4).  MALDI  mass  spectrometry  imaging  was  performed  on  tissue  sections  of  tumors  and  organs   subsequently   colonized   by   metastases.   Matrix   sublimation   was   used   to   coat   tumor   sections   (14   μm-­‐tick)   with   1.5   Diaminonaphthalene   (1.5   DAN)   for   lipids   analysis   and   Sinapinic   acid   (SA)   for   entire   proteins   analysis.   Ion   cartographies   were   recorded   with   a   Solarix9.4T   FTMS   instrument   for   lipids   and   with   an   Ultraflex   II   TOF-­‐TOF   instrument   for   entire   proteins   (BrukerDaltonics,   Bremen,   Germany)   with   a   spatial   resolution  of  100  μm.     The  analysis  of  differential  protein/lipid  profiles  with  high  mass  accuracy  and  broadband  resolution  allows   detection   of   intense   signals   from   lipid   families   such   as   Phosphatidylcholine   (PC),   Triglyceride   (TAG),   Sphingomyelin   (SM)   and   precise   lipid   droplets   or   tumor   cells   differentiated   location   in   the   Sunitinib   resistant   tumor   cells   compared   to   control   cells.The   protein   profiles   of   the   4   groups   of   mice   show   differences   in   intensity   and   location,   enabling   a   correlation   to   inflammatory   (highlighted   by   histological   staining)  and  angiogenic  phenomenon.   [less ▲]

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See detailMass spectrometry imaging is moving toward drug protein co-localization
Ait-Belkacem, Rima; Sellami, Lyna; Villard, Claude et al

in Trends in Biotechnology (2012), 30(9), 466-474

Mass spectrometry (MS)-based technology provides label-free localization of molecules in tissue samples. Drugs, proteins, lipids and metabolites can easily be monitored in their environment. Resolution ... [more ▼]

Mass spectrometry (MS)-based technology provides label-free localization of molecules in tissue samples. Drugs, proteins, lipids and metabolites can easily be monitored in their environment. Resolution can be achieved down to the cellular level (10–20 mm) for conventional matrix-assisted laser desorption/ionization (MALDI) imaging, or even to the subcellular level for more complex technologies such as secondary ionization mass spectrometry (SIMS) imaging. One question remains: are we going to be able to investigate functional relationships between drugs and proteins and compare with localized phenomena? This review describes the various spatial levels of investigation offered by mass spectrometry imaging (MSI), and the advantages and disadvantages compared with other labeling technologies. [less ▲]

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See detailQuantification of Acrylamide in Various Belgian Potato Products Using Solid Phase Extraction and Liquid Chromatography Tandem Mass Spectrometry Detection
Douny, Caroline ULg; Widart, Joëlle ULg; Maghuin-Rogister, Guy ULg et al

in Food and Public Health (2012), 2(5), 137-141

Acrylamide (CH2=CHCONH2), a neurotoxic and potentially carcinogenic substance for human health, is in the glare of the spotlights for a few years. This is mostly due to the fact that acrylamide was found ... [more ▼]

Acrylamide (CH2=CHCONH2), a neurotoxic and potentially carcinogenic substance for human health, is in the glare of the spotlights for a few years. This is mostly due to the fact that acrylamide was found worldwide in various heated foodstuffs. Levels reported in the literature vary from 25 to 2000 ìg/kg and potato products are considered as the most contaminated. A possible pathway of synthesis of acrylamide is the Maillard reaction between reducing sugars and the amino acid asparagine. The aim of this study was to develop a liquid chromatography/mass spectrometry method to analyse as quickly as possible acrylamide in a variety of Belgian food samples such as potatoes, French fries, crisp bread, coffee, corn-flakes, etc. The sample preparation consisted in a liquid/liquid extraction, a centrifugation, followed by purification with Solid Phase Extraction (SPE). The instruments used were a Waters 2690 Alliance HPLC system coupled to a Micro-mass Quattro Ultima Platinum triple-quadrupole mass spectrometer. The analysis was performed in MS/MS mode using isotopic dilution technique for quantification. An internal 13C3 labelled standard was added prior to extraction. Quantifica-tion in MS/MS mode was calculated by reconstructing the ion current with the most abundant daughter ions for native and 13C labelled standard (ions of m/z 55 and 58). [less ▲]

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See detailDistribution and identification of molecular interactions between tomato roots and bacterial biofilms
Debois, Delphine ULg; Jourdan, Emmanuel ULg; Smargiasso, Nicolas ULg et al

Conference (2012, September)

Some non pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in ... [more ▼]

Some non pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in soil (1). To initiate both phenomena leading to biocontrol activity, microorganisms use plant exudates to grow on roots and to produce in-situ active compounds. In Bacilli, cyclic lipopeptides of the surfactin, iturin and fengycin families represent important antibiotics involved in biocontrol (2). Recent studies in microbiology allowed a better understanding of plant microorganism interactions but few has been done at the molecular level. In this study, MALDI MS imaging has been used to study the nature of the secreted lipopeptide molecules, their relative quantity and their distribution in the root’s environment. Disinfected tomato seeds were first germinated at 28°C in sterile conditions for germination. Seedlings were then placed in Petri dish on ITO glass slide recovered with a thin layer of plant nutritive solution (Hoagland) containing 1,75% of agar and treated with freshly-grown cells of Bacillus amyloliquefaciens S499. Petri dishes were finally incubated vertically in phytotron at 28°C with a 16h photoperiod. Different root age / time of incubation were studied: 13 / 3; 13 / 7; 21 / 14 and 39 / 32. Control tomato root (without bacterial treatment) of the same ages were also analyzed (13 / 0; 21 / 0 and 42 / 0. For MALDI imaging experiments, the ITO slide was removed from the agar and dried in a dessiccator under vacuum. The matrix solution (α-cyano-hydroxycinnamic acid, 5mg/mL in ACN/0.2% TFA 70/30) was applied with an ImagePrep automated sprayer (Bruker Daltonics). An UltraFlex II TOF/TOF and a Solarix FT-ICR mass spectrometers were used to record molecular cartographies. The average mass spectra recorded around the tomato root (2-3 mm on both sides of the root) showed that lipopeptides were major compounds detected on the agar. The relative intensity of lipopeptides families varied with respect to the age of the root/biofilm system. In the 13/3 system, 3 homologues of surfactins were essentially detected (C13, C14 and C15), with very few iturins and fengycins. Their localizations were identical, whatever the considered homologue. Then the production of iturin and fengycin families increases in older systems (13/7 and 21/14) and a novel homologue of surfactin is detected (C12). Some variations in localizations within families may be observed (around the root or at the close vicinity of it in function of the considered homologue or alkali adduct). Then for the oldest system we studied, iturins and fengycins are not detected anymore and the localization of surfactins is less precise. In the 39/32 system, we also detected unknown compounds at 986.6, 1000.6, 1014.7 and 1028.7 m/z. The mass range of these compounds allied to the mass difference between two consecutive ion peaks let us think that these unknown compounds could be a new lipopeptide family. Investigations are in progress to identify these new secondary metabolites of Bacillus amyloliquefaciens. [less ▲]

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