References of "Laurent, Pascal"
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See detailAmphiphilic structure-surface property relationships of monosaccharide-based surfactants
Razafindralambo, Hary ULg; Nicks, Francois ULg; Richard, Gaetan ULg et al

Poster (2013, April 08)

A set of monosaccharide-based renewable surfactants has been prepared, structurally checked, and systematically screened for different activities and functionalities. These compounds vary in the polar ... [more ▼]

A set of monosaccharide-based renewable surfactants has been prepared, structurally checked, and systematically screened for different activities and functionalities. These compounds vary in the polar head group, linker, and hydrophobic tail. Beyond the goal to find out the most potential valuable surfactants for each measurement, relationships between chemical structure, basic properties, and functionalities have been examined by comparing compounds differing in a single structural variable. In this paper, we show and explain the impact of the anomeric alpha or bêta, neutral or acid sugar derivatives, equatorial or axial position of hydroxyl group, alkyl chain substitute attachment position, number, and length on surface properties of sugar-based surfactants. [less ▲]

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See detailEnzymatic synthesis and surface properties of novel rhamnolipids
Nott, Katherine ULg; Richard, Gaetan ULg; Laurent, Pascal ULg et al

in Process Biochemistry (2013), 48

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 ... [more ▼]

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. [less ▲]

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See detailAnalysis of calcium-induced effects on the conformation of fengycin
Nasir, Mehmet Nail ULg; Laurent, Pascal ULg; Flore, Christelle ULg et al

in Spectrochimica Acta Part A : Molecular and Biomolecular Spectroscopy (2013), 110

A combination of CD, FT-IR, NMR and fluorescence spectroscopic techniques was applied to elucidate the conformation of fengycin, a natural lipopeptide with antifungal and eliciting activities, in a ... [more ▼]

A combination of CD, FT-IR, NMR and fluorescence spectroscopic techniques was applied to elucidate the conformation of fengycin, a natural lipopeptide with antifungal and eliciting activities, in a membrane-mimicking environment and to investigate the effect of calcium ions on the conformation. We mainly observed that fengycin adopts a turn conformation and that the side chain of glutamate residues plays a key role on the stabilization of the peptide ring backbone conformation. More particularly, the binding of calcium ions by the carboxylic moieties has a consequence on the environment of the tyrosine residues. Our data suggest also an arrangement of fengycin molecules into “-sheet like micelles” in a membrane-mimicking environment and the enhancement of this aggregating effect in presence of calcium ions. The modulation of the fengycin conformation by the environmental conditions may influence its biological properties. [less ▲]

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See detailSynthesis and physico-chemical characterization of fatty esters
Sainvitu, Pauline ULg; Nott, Katherine ULg; Nicks, Francois ULg et al

Poster (2012, November 16)

Specific antioxidant molecules (e.g. phenolics) help to prevent oxidation reaction of the cell membrane. A fatty chain grafted on these compounds should enhance their capacity to interact with the ... [more ▼]

Specific antioxidant molecules (e.g. phenolics) help to prevent oxidation reaction of the cell membrane. A fatty chain grafted on these compounds should enhance their capacity to interact with the membrane lipids. In our study, three fatty esters comprising an aromatic part were synthesized. They differentiate the aromatic substituent and the number of carbons between the aromatic ring and the ester function. A structure-function relationships study was performed to identify the structural pattern affecting the interfacial properties and the membrane interaction properties. The behavior of their monolayer film at an air-water interface was studied. The interactions with membrane were assessed on living cells and were predicted by a computational approach. In the future, we will investigate the effect of the presence of a sugar unit on these molecules. [less ▲]

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See detailSynthesis and physico-chemical studies of glycine betaine derivatives
Laurent, Pascal ULg; NSimba Zakanda, Francis; Mvumbi Lelo, Georges et al

Poster (2012, October 11)

Design of new surfactants is of considerable interest in order to obtain materials with specific physico-chemical properties for targeted applications. Among them, quaternary ammonium surfactants are ... [more ▼]

Design of new surfactants is of considerable interest in order to obtain materials with specific physico-chemical properties for targeted applications. Among them, quaternary ammonium surfactants are widely employed in pharmaceutical and cosmetic industries. Unfortunately, as a consequence of their widespread use and strong resistance to biodegradation, those chemical surfactants may persist in wastewater treatment systems at relatively high concentrations and can cause a disturbance of the ecological equilibrium. In this context, glycine betaine based surfactants are of increasing interest today thanks to their higher biodegradability and low environmental impact. For example, alkylbetaines and alkylamidobetaines are produced on the industrial scale and are used as amphoteric surfactants less irritating compared to sodium dodecylsulfate (SDS) in cosmetics. In this study, new surface-active agents based on glycine betaine and issued from the green chemistry are synthesized. Very simple synthetic methodologies led to different betaine derivatives (esters, thioesters, amides). Their physico-chemical properties are investigated in order to give insights about the key parameters to take into account for the formulation of betaine derived compound preparations for cosmetic or pharmaceutical purposes. [less ▲]

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See detailMolecular analysis of the interfacial and membrane-interacting properties of D-xylose-based bolaforms
Nasir, Mehmet Nail ULg; Legrand, Vincent; Gatard, Sylvain et al

Poster (2012, October)

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See detailGreen synthesis and antioxidant activity of new PEGylated ferulic acids
Nicks, Francois ULg; Richel, Aurore ULg; Richard, Gaetan ULg et al

in Tetrahedron Letters (2012), 53(19), 2402-2405

PEGylation of ferulic acid is described through a green esterification process involving poly(ethylene glycol) (PEG) with three different average molecular weights (200, 400 and 1000 g/mol) as both ... [more ▼]

PEGylation of ferulic acid is described through a green esterification process involving poly(ethylene glycol) (PEG) with three different average molecular weights (200, 400 and 1000 g/mol) as both reactive and solvent. Esterification with PEG400 and PEG1000 leads to original compounds soluble in all proportions in water. These new compounds display an antioxidant activity similar to that of ferulic acid. [less ▲]

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See detailImpact of the alkyl chain carbon atom number of uronic acid-derivative surfactants on interfacial and colloidal systems
Razafindralambo, Hary ULg; Richard, Gaetan ULg; Laurent, Pascal ULg et al

Poster (2012, March 26)

Uronic acid-derivative surfactants represent today an attractive group of Carbohydrate-based amphiphilic compounds for both fundamental and practical reasons [1,2]. In the continuity of our screening of ... [more ▼]

Uronic acid-derivative surfactants represent today an attractive group of Carbohydrate-based amphiphilic compounds for both fundamental and practical reasons [1,2]. In the continuity of our screening of their basic properties, and the approach in establishing relationships between their structure and properties [3,4], the impact of the alkyl chain carbon atom number on interfacial and colloidal systems has been systematically investigated. In this communication, the effect of odd-even number of carbon atom from C11 to C18, and the particular behavior of long chain derivatives on interfacial properties, as well as their impact on the formation and stability of colloidal systems, are presented. Experimental approaches have been conducted by investigating their properties and behaviors at gas-liquid and liquid-liquid under dynamic, equilibrium, and oscillatory interfacial conditions. Results are completed by and discussed with single molecule models established by theoretical approaches. [1] Razafindralambo, H.;Blecker, C.; Paquot, M., Screening of Basic Properties of Amphiphilic Molecular Structures for Colloidal System Formation and Stability. In Amphiphiles: Molecular Assembly and Applications, American Chemical Society: 2011; Vol. 1070, pp 53-66. [2] Laurent, P.; Razafindralambo, H.; Wathelet, B.; Blecker, C.; Wathelet, J.; Paquot, M., Synthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials. J. Surfactants Deterg. 2011, 14, 51-63. [3] Razafindralambo, H.; Richel, A.; Wathelet, B.; Blecker, C.; Wathelet, J.; Brasseur, R.; Lins, L.; Miñones, J.; Paquot, M., Monolayer properties of uronic acid bicatenary derivatives at the air-water interface: effect of hydroxyl group stereochemistry evidenced by experimental and computational approaches. Physical chemistry chemical physics: PCCP 2011, 13 15291-15298. [4] Razafindralambo, H.; Blecker, C.; Mezdour, S.; Deroanne, C.; Crowet, J.; Brasseur,R.; Lins, L.; Paquot, M., Impacts of the Carbonyl Group Location of Ester Bond on Interfacial Properties of Sugar-Based Surfactants: Experimental and Computational Evidences. The journal of physical chemistry. B 2009, 113, 8872-8877. [less ▲]

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See detailFast-GC quantifacation of harmonine, the major defense alkaloid of the multicolored Asian ladybird Harmonia axyridis (Pallas)
Fischer, Christophe ULg; Laurent, Pascal ULg; Heuskin, Stéphanie ULg et al

in American Journal of Analytical Chemistry (2012), 3

These last few years the multicolored Asian ladybird, Harmonia axyridis (Pallas), previously introduced in Europe and North America as a biological control agent, has swiftly spread out on those ... [more ▼]

These last few years the multicolored Asian ladybird, Harmonia axyridis (Pallas), previously introduced in Europe and North America as a biological control agent, has swiftly spread out on those territories and turns out to be a pest in several ways. In order to improve understanding of several key points of the biology of this ladybird, a novel fast-GC method of quantification of harmonine, the main defense alkaloid of H. axyridis, has been designed and validated using the accuracy profile concept for concentrations ranging from 13 to 264 µg/individual. This method allows quantifying harmonine in a single insect with a maximal error risk of 20%. For ladybirds collected in spring, mean harmonine concentration observed was 106.6 µg/individual with a very high standard deviation of 80.2 µg/individual, which can easily be explained by the strong asymmetry of the results distribution. Males and females seem equally chemically protected as the harmonine concentration did not significantly differ between sexes. This method is currently used to improve our comprehension of several key points of H. axyridis biology including aggregation behavior and aposematism. [less ▲]

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See detailBiosynthesis of Defensive Coccinellidae Alkaloids: Incorporation of Fatty Acids in Adaline, Coccinelline, and Harmonine
Haulotte, Eveline; Laurent, Pascal ULg; Braekman, Jean-Claude

in European Journal of Organic Chemistry (2012), 10

In this study, we report on in vitro incorporation experiments of several labelled fatty acids in the ladybird alkaloids coccinelline (Coccinella 7-punctata), adaline (Adalia 2-punctata),and harmonine ... [more ▼]

In this study, we report on in vitro incorporation experiments of several labelled fatty acids in the ladybird alkaloids coccinelline (Coccinella 7-punctata), adaline (Adalia 2-punctata),and harmonine (Harmonia axyridis). The obtained resultsclearly indicate that stearic acid is the precursor of coccinelline and harmonine, whereas myristic acid is at the origin of the carbon skeleton of adaline. Possible pathways for the biosynthesis of these alkaloids are presented. [less ▲]

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See detailEfficient microwave-promoted synthesis of glucuronic and galacturonic acid derivatives using sulfuric acid impregnated on silica
Richel, Aurore ULg; Nicks, Francois ULg; Laurent, Pascal ULg et al

in Green Chemistry Letters & Reviews (2012), 5(2), 179-186

Monomode microwave-assisted syntheses of D-glucuronic and D-galacturonic acid derivatives are reported in the presence of a solid acid catalyst, consisting of sulfuric acid loaded onto silica. This ... [more ▼]

Monomode microwave-assisted syntheses of D-glucuronic and D-galacturonic acid derivatives are reported in the presence of a solid acid catalyst, consisting of sulfuric acid loaded onto silica. This approach affords a variety of surface-active monoglycosylated glucofuranosidurono-6,3-lactones and disubstituted galacturonic adducts in excellent yields in less than 10 min at 85 °C. This study illustrates the application of microwave heating mode, in combination with a cost-effective solid catalyst, as an efficient, selective and eco-friendly methodology in carbohydrate chemistry. [less ▲]

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See detailBINDING INTERACTIONS OF URONIC ACID DERIVATIVES TO LIPID VESICLES INVESTIGATED BY ISOTHERMAL TITRATION CALORIMETRY
Razafindralambo, Hary ULg; Laurent, Pascal ULg; Wathelet, Jean-Paul ULg et al

Poster (2011, November 12)

Uronic acid derivatives (UAD) constitute a particular class of carbohydrate-based small compounds, which are receiving growing interests today for many reasons. Beyond their excellent environmental ... [more ▼]

Uronic acid derivatives (UAD) constitute a particular class of carbohydrate-based small compounds, which are receiving growing interests today for many reasons. Beyond their excellent environmental compatibility, their potentiality mainly arises from the large abundance of their precursors from renewable resources, and the quasi-unlimited availability of their molecular structure and geometry [1]. Such a structural diversity allows them to be a typical compound class for the structure-activity relationship investigation using simplest models. This approach is very important for predicting their functionalities and activities. Among others, searching specific and potent biological activities against target molecules, cells, and micro-organisms is a big challenge today. In this context, binding interactions of three UAD having different hydrophobic residues (allyl, benzyl, and cyclohexyl) to 1-palmitoyl-2-oleyl-sn-glycerol-3-phosphatidylcholine (POPC) vesicles have been investigated using Isothermal Titration Calorimetry (ITC) technique [2]. The binding affinity (Ka) to the membrane model at 25°C has been determined and compared for the three compounds. Based on thermograms resulting from UAD aqueous solution titration experiments, with and without POPC vesicles, it clearly appears that both derivatives with a cyclic residue interact stronger with the lipid membrane model than their linear derivative counter-part, which exhibits almost no interaction. Moreover, the derivative compound with a cyclohexyl residue saturates faster POPC vesicles than that with a benzyl residue. We conclude that: (a) UAD having a cyclic hydrophobic residue, either saturated or unsaturated, bind more easily to the lipid membrane model than a linear one ending with a double bond; (b) the greater the number of hydrogen in the UAD residue chemical structure (saturated bonds), the stronger their binding affinity to POPC vesicles, suggesting the importance of H-bonding to such a lipid membrane model. The Ka mean value of the best tested UAD, i.e. with a cyclohexyl residue, is about 5.103 M-1. [1] Razafindralambo, H.; Blecker, C; and M. Paquot., Screening of basic properties of amphiphilic molecular the structures for colloidal system formation and stability: the case of carbohydrate-based surfactants in: Amphiphiles: Molecular Assembly and Applilcations, ed. R. Nagarajan, ACS, Washignton, 2011, (In press). [2] Razafindralambo, H.; Dufour, S.; Paquot, M.; Deleu, M., Thermodynamic studies of the binding interactions of surfactin analogues to lipid vesicles: application of isothermal titration calorimetry. J. Therm. Anal. Calorim., 2009, 9 (3), 817-821. Acknowledgment: This work was supported by Belgian Walloon Region with DG06 research project of excellence (TECHNOSE). [less ▲]

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See detailLipase catalysis and thiol-Michael addition: a relevant association for the synthesis of new surface active carbohydrate esters
Boyère, Cédric ULg; Favrelle, Audrey ULg; Broze, Guy ULg et al

in Carbohydrate Research (2011), 346(14), 2121-2125

A novel class of surface-active carbohydrate esters is prepared by a two-step strategy that takes advantage of the selectivity of enzymatic catalysis and the versatility of the thiol-Michael addition ... [more ▼]

A novel class of surface-active carbohydrate esters is prepared by a two-step strategy that takes advantage of the selectivity of enzymatic catalysis and the versatility of the thiol-Michael addition reaction. The surfactant performance of the produced aliphatic, fluorinated and silicon based sugar esters are evaluated by surface tension measurements. The novel thiolated mannose, made available in this work, appears as a powerful building block for the incorporation of unprotected sugar moieties into complex molecules. [less ▲]

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See detailEnzymatic synthesis and surface active properties of novel hemifluorinated mannose esters
Favrelle, Audrey ULg; Boyère, Cédric ULg; Laurent, Pascal ULg et al

in Carbohydrate Research (2011), 346(9), 1161-1164

The lipase-catalysed esterification of sugars with hemifluorinated acid derivatives is reported for the first time. A series of mannose modified derivatives having fluorinated chains with different length ... [more ▼]

The lipase-catalysed esterification of sugars with hemifluorinated acid derivatives is reported for the first time. A series of mannose modified derivatives having fluorinated chains with different length have been prepared accordingly in moderate yield. A preliminary evaluation of the surface active properties of these hemifluorinated mannose esters revealed their ability to reduce the surface tension of water much more efficiently than their aliphatic counterparts. [less ▲]

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See detailDiallyl disulfides: comparison between classical and microwave assisted synthesis
DETHIER, Bérénice ULg; Richel, Aurore ULg; Laurent, Pascal ULg et al

Poster (2011, June)

Garlic contains organosulfur compounds, such as diallyl disulfides (DADS), diallyl monosulfides (DAMS) and diallyl trisulfides (DATS), which have potential health properties. The first objective of this ... [more ▼]

Garlic contains organosulfur compounds, such as diallyl disulfides (DADS), diallyl monosulfides (DAMS) and diallyl trisulfides (DATS), which have potential health properties. The first objective of this work is to conduct the synthesis of these molecules by heating in a classical oil bath or by microwave irradiation with a phase transfer catalyst. We concluded that the synthesis should be cnducted at 40°C in an oil bath, with a phase transfer catalyst. [less ▲]

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See detailStructure-Surface Activity Relationships Of Uronic Acid-Derivative Surfactants From Renewable Resources Applications
Razafindralambo, Hary ULg; Richel, Aurore ULg; Richard, Gaetan ULg et al

Poster (2011, June)

Introduction and Background: Uronic acid-derivative surfactants are amphiphilic compounds with growing interests owing to their potential applications in various areas [1]. This class of carbohydrate ... [more ▼]

Introduction and Background: Uronic acid-derivative surfactants are amphiphilic compounds with growing interests owing to their potential applications in various areas [1]. This class of carbohydrate-based surfactants can be easily prepared from renewable raw materials in a wide range of structure by modular synthesis thanks to the presence of one carboxylic and numerous hydroxyl groups. The polar head group configurations according to the stereochemistry of OH groups, and geometry (cyclic or not), the hydrophobic tail (number and length of alkyl chain), and the type of linker (ester, acetal and amide, etc) are among the main variables in their structural entities. Therefore, the investigation of their structure-surface activity relationships appears valuable for increasing backgrounds, and achieving a rational design for selecting the best structures to be used in different industrial fields [2]. Methodology: A few analogous of glucuronic acid-derivative surfactants have been synthesized by chemical or enzymatic routes. After purification, their structure has been confirmed by various spectroscopic techniques (RMN, MS, IR). Surface tensions of true aqueous solution have been then measured in dynamic and static modes using a series of complementary techniques. Critical micelle concentrations, minimum molecular areas, and maximum surface excesses have also been determined. Results and Discussion: Glucuronic acid derivative surfactants under investigation vary in the polar head group configuration including cyclic or non-cyclic structure and α or β anomeric form, in the hydrophobic tail regarding to the chain length (C8 to C14), the presence of a double bond, as well as an OH group at the terminal carbon, and in the type of linker, ester in C6 or acetal in C1. Results showed that all of these structural attributes affect both dynamic and equilibrium surface properties of glucuronic acid -based surfactants. Conclusion: A set of synthetic glucuronic acid-based surfactants varying in the polar head group, hydrophobic tail, and linker allow us to generate various surface-active properties at the air-water interface, and to increase the knowledge on relationships between their structure and surface-active properties. [1] Laurent, P.; Razafindralambo, H.; Wathelet, B.; Blecker, C.; Wathelet, J.-P.; Paquot, M., Synthesis and Surface-Active Properties of Uronic Amide Derivatives, Surfactants from Renewable Organic Raw Materials. Journal of Surfactants and Detergents 2010, in press. [2] Razafindralambo, H.; Blecker, C.; Mezdour, S.; Deroanne, C.; Crowet, J.; Brasseur, R.; Lins, L.; Paquot, M., Impacts of the Carbonyl Group Location of Ester Bond on Interfacial Properties of Sugar-Based Surfactants: Experimental and Computational Evidences. The Journal of Physical Chemistry B 2009, 113 (26), 8872-8877. Acknowledgment: This work was supported by Belgian Walloon Region within DGTRE research project of excellence (TECHNOSE). [less ▲]

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See detailLipase-catalyzed synthesis of L-cysteine glucosyl esters in organic media
Valepyn, Emmanuel ULg; Nys, Joël ULg; Richel, Aurore ULg et al

in Biocatalysis & Biotransformation (2011), 29(1), 25-30

New sugar amino acids were synthesized by enzymatic esterification of D -glucose with L -cysteine using immobilized lipase B from Candida antarctica in a mixed solvent system composed of 2-methyl-2 ... [more ▼]

New sugar amino acids were synthesized by enzymatic esterification of D -glucose with L -cysteine using immobilized lipase B from Candida antarctica in a mixed solvent system composed of 2-methyl-2-butanol and dimethyl sulfoxide. Addition of small quantities of water to the medium improved the glucose conversion yield by a factor of two. [less ▲]

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See detailLe bioraffinage, une alternative prometteuse à la pétrochimie
Laurent, Pascal ULg; Roiz, Julie ULg; Wertz, Jean-Luc ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2011), 15(4), 597-610

Because of the price increase of fossil resources, of their uncertain availability and because of environmental concerns, alternative solutions able to mitigate global warming, and reduce the consumption ... [more ▼]

Because of the price increase of fossil resources, of their uncertain availability and because of environmental concerns, alternative solutions able to mitigate global warming, and reduce the consumption of fossil fuels and carbon dioxide emissions should be promoted. The replacement of petroleum with biomass as raw material for bioenergy (biofuels, power and heat) and chemical production is an interesting option and is the driving force for the development of biorefinery complexes that will have a critical role to play in our common future. A biorefinery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, heat and chemicals from biomass. In biorefinery, almost all types of biomass feedstocks can be converted to different classes of biofuels and biochemicals through various processes that maximize economic and environmental benefits, while minimizing waste and pollution. Through the integration of green chemistry into biorefineries, and the use of low environmental impact technologies, future sustainable production chains of biofuels and high value chemicals from biomass can therefore be established. Currently, the green biorefinery, the whole-crop biorefinery, the oilseed biorefinery and the lignocellulosic feedstock biorefinery are favoured in research, development and industrial implementation, essentially through fully integrated biorefinery complexes. [less ▲]

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