http://hdl.handle.net/2268/151 Chercher dans ce canal chercher http://orbi.ulg.ac.be/simple-search http://hdl.handle.net/2268/149150 Titre: Synthesis and catalytic application of palladium imidazol(in)ium-2- dithiocarboxylate complexes <br/> <br/>Auteur, co-auteur: Champion, Martin J. D.; Solanki, Riten; Delaude, Lionel; White, Andrew J. P.; Wilton-Ely, James D. E. T. <br/> <br/>Résumé: The palladium(ii) dimer, [Pd(C,N-C 6H 4CH 2NMe 2)Cl] 2 reacts with two equivalents of the NHC·CS 2 zwitterionic ligands [NHC = IPr (1,3- diisopropylimidazol-2-ylidene), ICy (1,3-dicyclohexylimidazol-2-ylidene), IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IDip (1,3-bis(2,6- diisopropylphenyl)imidazol-2-ylidene), SIMes (1,3-bis(2,4,6-trimethylphenyl) imidazolin-2-ylidene)] in the presence of NH 4PF 6, to yield the cationic products [Pd(C,N-C 6H 4CH 2NMe 2)(S 2C·NHC)] +. In a similar fashion, the compounds [Pd(C,N-bzq)(S 2C·NHC)] + (bzq = benzo[h]quinolinyl, NHC = ICy, IMes, IDip) are obtained from the corresponding dimer [Pd(C,N-bzq)Cl] 2. The bis(phosphine) compounds [Pd(S 2C·NHC)(PPh 3) 2] 2+ (NHC = ICy, IMes, IDip, SIMes) are obtained on treatment of [PdCl 2(PPh 3) 2] with NHC·CS 2 zwitterions in the presence of NH 4PF 6. The reaction of [PdCl 2(dppf)] with IMes·CS 2 and NH 4PF 6 provides the complex [Pd(S 2C·IMes)(dppf)] 2+. The complexes [Pd(S 2C·NHC)(PPh 3) 2](PF 6) 2 (NHC = IMes, IDip) were active pre-catalysts (1 mol% loading) for the conversion of benzo[h]quinoline to 10-methoxybenzo[h]quinoline in the presence of PhI(OAc) 2 and methanol. The intermediacy of [Pd(C,N-bzq)(S 2C·NHC)] + was supported by the high yield of 10-methoxybenzo[h]quinoline using [Pd(C,N-bzq)(S 2C·IDip)] + to promote the same reaction. Small amounts of 2,10-dimethoxybenzo[h]quinoline were also isolated from these reactions. Using [Pd(C,N-bzq)(S 2C·IDip)] + and N-chlorosuccinimide as the oxidant led to the formation of 10-chlorobenzo[h]quinoline in moderate yield from benzo[h]quinoline. The molecular structures of [Pd(S 2C·IMes)(PPh 3) 2](PF 6) 2 and [Pd(S 2C·IMes) (dppf)](PF 6) 2 were determined crystallographically. http://hdl.handle.net/2268/149149 Titre: Assessing the ligand properties of 1,3-dimesitylbenzimidazol-2-ylidene in ruthenium-catalyzed olefin metathesis <br/> <br/>Auteur, co-auteur: Borguet, Yannick; Zaragoza, Guillermo; Demonceau, Albert; Delaude, Lionel <br/> <br/>Résumé: The deprotonation of 1,3-dimesitylbenzimidazolium tetrafluoroborate with a strong base afforded 1,3-dimesitylbenzimidazol-2-ylidene (BMes), which was further reacted in situ with rhodium or ruthenium complexes to afford three new organometallic products. The compounds [RhCl(COD)(BMes)] (COD is 1,5-cyclooctadiene) and cis-[RhCl(CO)2(BMes)] were used to probe the steric and electronic parameters of BMes. Comparison of the percentage of buried volume (%VBur) and of the Tolman electronic parameter (TEP) of BMes with those determined previously for 1,3-dimesitylimidazol-2-ylidene (IMes) and 1,3-dimesitylimidazolin-2-ylidene (SIMes) revealed that the three N-heterocyclic carbenes (NHCs) had very similar profiles. Nonetheless, changes in the hydrocarbon backbone subtly affected the stereoelectronic properties of these ligands. Accordingly, the corresponding [RuCl2(PCy 3)(NHC)(CHPh)] complexes displayed different catalytic behaviors in the ring-closing metathesis (RCM) of α,ω-dienes. In the benchmark cyclization of diethyl 2,2-diallylmalonate, the new [RuCl2(PCy 3)(BMes)(CHPh)] compound (1d) performed slightly better than the Grubbs second-generation catalyst (1a), which was in turn significantly more active than the related [RuCl2(PCy3)(IMes)(CHPh)] initiator (1b). For the formation of a model trisubstituted cycloolefin, complex 1d ranked in-between catalyst precursors 1a and 1b, whereas in the RCM of tetrasubstituted cycloalkenes it lost its catalytic efficiency much more rapidly. http://hdl.handle.net/2268/149089 Titre: Macroporous poly(ionic liquid)s and poly(acrylamide)s monoliths from CO2-in-water emulsion templates stabilized by sugar-based surfactants <br/> <br/>Auteur, co-auteur: Boyère, Cédric; Favrelle, Audrey; Léonard, Alexandre; Boury, Frank; Jérôme, Christine; Debuigne, Antoine <br/> <br/>Résumé: Highly interconnected poly(acrylamide) (PAM) and poly(vinylimidazolium) (PVIm) porous monoliths were templated by carbon 10 dioxide-in-water (CO2/W) high internal phase emulsions (HIPEs), a toxic-solvent free process. A range of sugar-based fluorinated surfactants prepared by chemoenzymatic synthesis were used as emulsifiers. Both the concentration and the structure of the surfactants, especially the length of their CO2-philic part and of their spacer between the sugar head and the tail, were found to strongly affect the cellular structure and morphology of the PAM polyHIPEs, i.e. the size of pores and cells. A mannose derivative bearing a chain ranging from 6 to 10 perfluorinated carbons and a long spacer emerged as the best stabilizer, leading to a porous monolith with average pores and 15 cells sizes (about 2.6 1m and 5-10 1m, respectively) among the lowest reported for polyHIPEs produced from CO2/W emulsions. The same template then served for the preparation of the first macroporous poly(ionic liquid)s (PILs) polyHIPE by using 1-vinyl-3- ethylimidazolium bromide as monomer. Shrinkage of the final material was prevented by adjusting the divinylimidazolium crosslinker content. The resulting low density polyHIPE exhibits small spherical cells (~5 1m) connected by numerous small pores (~2 1m), confirming that the CO2/W HIPE templating methodology based on fluorinated glycosurfactants is a technique of choice for the 20 preparation of macroporous PILs. http://hdl.handle.net/2268/149082 Titre: Effect of head-to-head addition in vinyl acetate controlled radical polymerization: why is Co(acac)2-mediated polymerization so much better? <br/> <br/>Auteur, co-auteur: Morin, Aurélie N.; Detrembleur, Christophe; Jérôme, Christine; De Tullio, Pascal; Poli, Rinaldo; Debuigne, Antoine <br/> <br/>Résumé: The controlled polymerization of vinyl acetate has been recently achieved by several techniques, but PVAc with targeted Mn and low dispersity up to very high monomer conversions and high degrees of polymerization was only obtained with Co(acac)2 as controlling agent in the so-called CMRP, a type of organometallic mediated radical polymerization (OMRP). Other techniques (including ATRP, ITP, TERP, and RAFT/MADIX) have shown a more or less pronounced slowdown in the polymerization kinetics, which was attributed to the higher strength of the C−X bond between the radical PVAc chain and the trapping agent (X) in the dormant species and to a consequent slower reactivation after a less frequent head-to-head monomer addition. The reason for the CMRP exception is clarified by the present contribution. First, a detailed investigation by 1H, 13C and multiplicity-edited HSQC and DEPT-135 NMR of the PVAc obtained by CMRP, in comparison with a regular polymer made by free radical polymerization under the same conditions, has revealed that Co(acac)2 does not significantly alter the fraction of head-to-head sequences in the polymer backbone and that there is no accumulation of Co(acac)2-capped chains with a head-to-head ω end. Hence, both dormant chains (following the head-to-head and the head-to-tail monomer additions) must be reactivated at similar rates. A DFT study shows that this is possible because the dormant chains are stabilized not only by the C−Co σ bond but also by formation of a chelate ring through coordination of the ω monomer carbonyl group. The head-to-head dormant chain contains an inherently stronger C−Co bond but forms a weaker 6-membered chelate ring, whereas the weaker C−Co bond in the head-to-tail dormant chain is compensated by a stronger 5-membered chelate ring. Combination of the two effects leads to similar activation enthalpies, as verified by DFT calculations using a variety of local, gradient-corrected, hybrid and “ad hoc” functionals (BPW91, B3PW91, BPW91*, M06 and M06L). While the BDE(C−X) of model H-VAc−X molecules [X = Cl, I, MeTe, EtOC(S)S and Co(acac)2] are functional dependent, the BDE difference between head-to-head and head-to-tail dormant chain models is almost functional insensitive, with values of 5−9 kcal/mol for the ATRP, ITP and TERP models, 3−6 for the RAFT/MADIX model, and around zero for CMRP. http://hdl.handle.net/2268/149012 Titre: Light-induced Hetero-Diels Alder cycloaddition as a new coupling method to biomolecule radiolabeling <br/> <br/>Auteur, co-auteur: Dammicco, Sylvestre; Luxen, André; Thonon, David; Flagothier, Jessica; Warnier, Corentin <br/> <br/>Résumé: The formation of a C-18F bond requires hard conditions which is problematic for the biomolecule radiolabelling. The alternative method which has been developed since a few decades consists in incorporating the 18F on a prosthetic group and coupling it to the biomolecule. The copper (I)-catalysed 1,2,3-triazole formation involving azides and terminal alkynes is a powerful and rapid method of coupling but present the inconvenient of the employment of cytotoxic reagents. The photoclick conjugation is a promising alternative with no need of catalyst[1]. Recently, a light-induced hetero-Diels Alder cycloaddition involving a 3-(hydroxymethyl)-2-naphthol derivative and an electron-rich olefin has been developed[2]. This reaction seems well adapted for the fast conjugation of radionuclides to biomolecules. Herein we report the synthesis of a [18F]fluoronaphtoquinone derivative as prosthetic group and its reaction with vinyl ethers. http://hdl.handle.net/2268/149010 Titre: Fluorine-18 labeling of biocompatible nanoparticles for PET imaging <br/> <br/>Auteur, co-auteur: Kaisin, Geoffroy; Warnier, Corentin; Luxen, André http://hdl.handle.net/2268/149006 Titre: Synthesis of [18F]4-(4-fluorophenyl)-1,2,4-triazole-3,5-dione: an agent for specific radiolabelling of tyrosine. <br/> <br/>Auteur, co-auteur: Flagothier, Jessica; Warnier, Corentin; Lemaire, Christian; Luxen, André <br/> <br/>Résumé: Objectives: Metal-free and mild tyrosine modification reactions are an attractive alternative to the commonly used lysine and cysteine modification protocols for peptide and proteins labelling. Recently, Ban and co-workers have reported a tyrosine bioconjugation through ene-type reactions. Cyclic diazodicarboxamides, which are electrophilic compounds, react selectively in o-position on the phenol side chain of tyrosine in mild aqueous conditions and the 1,2,4-triazolidine-3,5-dione linkage is hydrolytically and thermally stable. We herein present the synthesis of [18F]4-(4-fluorophenyl)-1,2,4-triazole-3,5-dione and the coupling with N-acyl tyrosine methylamide. Methods: The N,N,N-trimethyl-4-nitrobenzeneammonium trifluoromethanesulfonate 1 was prepared following a procedure previously reported [2]. The [18F]prosthetic group 6, [18F]4-(4-fluorophenyl)-1,2,4-triazole-3,5-dione, was synthesized in five steps. Results: The synthesis of the [18F]prosthetic group has been realized with a decay-corrected radiochemical yield of 20% in 90 minutes. The radiochemical yield of the coupling with N-acyl tyrosine methylamide is 40% (DC). This presented synthetic pathway should be easily automated: particulary because the purifications between the different steps are exclusively done on SPE cartridges. Conclusions: We successfully developed an efficient bioconjugation method for fluorine-18 labelling of tyrosine without prior modifications of the peptide in very mild conditions. http://hdl.handle.net/2268/148834 Titre: Les enzymes et leur utilisation en biotechnologie industrielle <br/> <br/>Auteur, co-auteur: Galonde, Nadine http://hdl.handle.net/2268/148792 Titre: Identification and functional characterization of a novel αlpha-conotoxin (EIIA) from Conus ermineus <br/> <br/>Auteur, co-auteur: Quinton, Loïc; Servent, Denis; Girard, Emmanuelle; Molgo, Jordi; Le Caër, Jean-Pierre; Malosse, Christian; Haidar, El Ali; Lecoq, Alain; Gilles, Nicolas; Chamot-Rooke, Julia <br/> <br/>Résumé: Nicotinic acetylcholine receptors (nAChRs) are one of the most important families in the ligand-gated ion channel superfamily due to their involvement in primordial brain functions and in several neurodegenerative pathologies. The discovery of new ligands which can bind with high affinity and selectivity to nAChR subtypes is of prime interest in order to study these receptors and to potentially discover new drugs for treating various pathologies. Predatory cone snails of the genus Conus hunt their prey using venoms containing a large number of small, highly structured peptides called conotoxins. Conotoxins are classified in different structural families and target a large panel of receptors and ion channels. Interestingly, nAChRs represent the only subgroup for which Conus has developed seven distinct families of conotoxins. Conus venoms have thus received much attention as they could represent a potential source of selective ligands of nAChR subtypes. We describe the mass spectrometric based approaches which led to the discovery of a novel α-conotoxin targeting muscular nAChR from the venom of Conus ermineus. The presence of several posttranslational modifications complicated the N-terminal sequencing. To discriminate between the different possible sequences, analogs with variable N-terminus were synthesized and fragmented by MS/MS. Understanding the fragmentation pathways in the low m/z range appeared crucial to determine the right sequence. The biological activity of this novel α-conotoxin (α-EIIA) that belongs to the unusual α4/4 subfamily was determined by binding experiments. The results revealed not only its selectivity for the muscular nAChR, but also a clear discrimination between the two binding sites described for this receptor. http://hdl.handle.net/2268/148791 Titre: Peptide backbone fragmentation initiated by side-chain loss at cysteine residue in matrixassisted laser desorption/ionization in-source decay mass spectrometry <br/> <br/>Auteur, co-auteur: Asakawa, Daiki; Smargiasso, Nicolas; Quinton, Loïc; De Pauw, Edwin <br/> <br/>Résumé: Matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) is initiated by hydrogen transfer from matrix molecules to the carbonyl oxygen of peptide backbone with subsequent radical-induced cleavage leading to c0/z• fragments pair. MALDI-ISD is a very powerful method to obtain long sequence tags from proteins or to do de novo sequencing of peptides. Besides classical fragmentation, MALDI-ISD also shows specific fragments for which the mechanism of formation enlightened the MALDI-ISD process. In this study, the MALDI-ISD mechanism is reviewed, and a specific mechanism is studied in details: the N-terminal side of Cys residue (Xxx-Cys) is described to promote the generation of c0 and w fragments in MALDI-ISD. Our data suggest that for sequences containing Xxx-Cys motifs, the N–Ca bond cleavage occurs following the hydrogen attachment to the thiol group of Cys side-chain. The c•/w fragments pair is formed by side-chain loss of the Cys residue with subsequent radical-induced cleavage at the N–Ca bond located at the left side (N-terminal direction) of the Cys residue. This fragmentation pathway preferentially occurs at free Cys residue and is suppressedwhen the cysteines are involved in disulfide bonds. Hydrogen attachment to alkylated Cys residues using iodoacetamide gives free Cys residue by the loss of •CH2CONH2 radical. The presence of alkylated Cys residue also suppress the formation of c•/w fragments pair via the (Cb)-centered radical, whereas w fragment is still observed as intense signal. In this case, the z• fragment formed by hydrogen attachment of carbonyl oxygen followed side-chain loss at alkylated Cys leads to a w fragment. Hydrogen attachment on peptide backbone and side-chain of Cys residue occurs therefore competitively during MALDI-ISD process. http://hdl.handle.net/2268/148636 Titre: Quantization of pore corrugation in SBA-15 by image analysis of electron tomograms <br/> <br/>Auteur, co-auteur: Friedrich, Heiner; Gommes, Cédric; de Jongh, Petra; de Jong, Krijn http://hdl.handle.net/2268/148635 Titre: 15 Minutes about SAXS and gels <br/> <br/>Auteur, co-auteur: Gommes, Cédric; Goderis, Bart; Pirard, Jean-Paul http://hdl.handle.net/2268/148633 Titre: SAXS Data Analysis of Ordered and Disordered Morphologies With Gaussian Random Field Models <br/> <br/>Auteur, co-auteur: Gommes, Cédric; Goderis, Bart http://hdl.handle.net/2268/148632 Titre: Characterization of nanometer-scale roughness in SBA-15 mesoporous silica using image analysis of electron tomograms <br/> <br/>Auteur, co-auteur: Friedrich, Heiner; Gommes, Cédric; de Jongh, Petra; de Jong, Krijn http://hdl.handle.net/2268/148539 Titre: Optimization of the formation of vinyldithiins, therapeutic compounds from garlic <br/> <br/>Auteur, co-auteur: DETHIER, Bérénice; Hanon, Emilien; Maayoufi, Said; Nott, Katherine; Fauconnier, Marie-Laure <br/> <br/>Résumé: Allyl sulfides, ajoenes and vinyldithiins are the three main groups of volatile organosulfur compounds that are formed when garlic is crushed. The manner garlic is processed (nature of the extraction medium, temperature…) has a major influence on their relative proportion and the amounts produced. It has been proven recently that the vinyldithiins are at the origin of garlic’s capacity to prevent adipocytes development. Their incorporation in garlic-based nutraceuticals is thus particularly interesting. In this context, this work aims to optimize the production of vinyldithiins from garlic. After having determined the best garlic origin (Spanish) and the best oil for the extraction (olive or sunflower oil), the extraction conditions were optimized (1/2 (w/w garlic oil), 37 °C, 6 h) and 133 mg of vinyldithiins was obtained from 100 g of fresh garlic. Carrying out the extraction under microwave irradiation allowed increasing the yield 3.6-fold (yield 486 mg of vinyldithiins from 100 g of fresh garlic). This study may also contribute to the development of new garlic derived high value products by enhancing the comprehension of their formation. http://hdl.handle.net/2268/148521 Titre: Preparation of new organoclays in supercritical carbon dioxide and their industrial potential in polymer nanocomposites <br/> <br/>Auteur, co-auteur: Naveau, Elodie http://hdl.handle.net/2268/148490 Titre: Enzymatic synthesis, surface and lipid interaction properties of novel rhamnolipids <br/> <br/>Auteur, co-auteur: Nott, Katherine; Richard, Gaetan; Deleu, Magali <br/> <br/>Résumé: Amongst glycolipidid biosurfactants, rhamnolipids have drawn particular attention as they have several interesting biological properties such as antimicrobial, antiphytoviral, zoosporicidal and plant defense elicitor activities [1-3]. It is generally recognised that these activities must be linked to the interaction of these molecules with constituents of biological membranes [4] but the detailed mechanism is far from being fully understood. The objective of this work is double. First, it aims to investigate a new strategy of synthesis for the production of novel rhamnolipids [5] that could exhibit properties as promising for industrial and environmental applications as their natural counterparts while avoiding the use of the pathogenic Pseudomonas aeruginosa for their production. Secondly, their basic surface properties (critical aggregation concentration, surface tension at CAC and interfacial behaviour of their monolayer) and their interaction with model membranes are investigated in relation with their structure in order to give insight about the mechanism of their biological actions. [1] Vatsa P. et al. Int. J. Mol. Sci. 2010;11:5095. [2] Varnier A-L. et al. Plant, Cell Environ. 2009;32:178. [3] Lang S. et al. Appl. Microbiol. Biotechn. 1999;51:22. [4] Aranda F.J. et al. Langmuir. 2007;23:2700. [5] Nott K. et al. Process Biochemistry, http://dx.doi.org/10.1016/j.procbio.2012.11.019 http://hdl.handle.net/2268/148426 Titre: Structural characterization of disulfide-bridged-peptides by a combined use of ETD and Ion-Mobility mass spectrometry <br/> <br/>Auteur, co-auteur: Massonnet, Philippe; Quinton, Loïc; Smargiasso, Nicolas; Gilles, Nicolas; De Pauw, Edwin http://hdl.handle.net/2268/148363 Titre: Electroinitiated polymerization <br/> <br/>Auteur, co-auteur: Jérôme, Christine <br/> <br/>Résumé: Electroinitiated polymerization, a method particularly relevant in coating technology, offers the unique opportunity of imparting permanent functionality/reactivity to a variety of surfaces, provided that the solid substrate is (semi)conducting. By focusing on the electroinitiation of acrylic monomers, basic concepts and some tools dedicated to the analysis of this peculiar polymerization process are discussed in this chapter. The important role of this polymerization method in the field of conjugated polymers is also highlighted. Finally, this chapter concludes with the opportunities and future challenges of this technology. http://hdl.handle.net/2268/148128 Titre: Enzymatic synthesis and surface properties of novel rhamnolipids <br/> <br/>Auteur, co-auteur: Nott, Katherine; Richard, Gaetan; Laurent, Pascal; Jérôme, Christine; Blecker, Christophe; Wathelet, Jean-Paul; Paquot, Michel; Deleu, Magali <br/> <br/>Résumé: New rhamnolipids were obtained via the development of a synthesis procedure consisting of two biocatalyzed steps. In the first step, naringinase was used to introduce a primary alcohol function onto rhamnose by glycosylation of 1,3-propanediol. In the second step, immobilized lipase B from Candida antarctica catalyzed the esterification of the primary hydroxyl group with mono- and di-carboxylic fatty acids of increasing chain length (from C8 to C14). For the monoic acids, the initial rate and 24 h yield decreased with increasing chain length. For the dioic acid, the number of carbon atoms of the acid did not influence these parameters. The new rhamnolipid obtained with tetradecanoic acid showed very good surface properties. At pH 5, it had a very low critical aggregation concentration of 1.70 M and it diminished water’s surface tension to 27.6 mN/m. It was also able to form stable insoluble monolayers. On the other hand, the rhamnolipid formed with tetradecanedioic acid showed far less interesting surface properties.