Bolaamphiphiles Derived from Alkenyl L-rhamnosides and Alkenyl D-xylosides: Importance of the Hydrophilic Head

in Molecules (2013), 18(5), 6101-6112

The two step synthesis of a new bolaamphiphile derived from alkenyl L-rhamnosides was described. The general synthetic strategy of bolaamphiphiles derived from L-rhamnose was based on a previous work ... [more ▼]

The two step synthesis of a new bolaamphiphile derived from alkenyl L-rhamnosides was described. The general synthetic strategy of bolaamphiphiles derived from L-rhamnose was based on a previous work describing the synthesis of bolaamphiphiles derived from D-xylose. The conformational properties of this new compound were investigated by FTIR spectroscopy in an aqueous film in order to obtain a reference for further studies about the membrane-interacting properties. Moreover, the surface activity of this new bolaamphiphile was analyzed by Langmuir balance technology and was compared with that of the analogous bolaamphiphile derived from alkenyl D-xylosides. The findings indicate that the rhamnoside-based bolaform has an increased surface activity and a better ability to form aggregates than xyloside-based one. [less ▲]

Influence of the 524-VAAEIL-529 sequence of annexins A6 in their interfacial behavior and interaction with lipid monolayers.

in Journal of Colloid & Interface Science (2013), In Press

Annexin A6 (AnxA6), a calcium- and membrane-binding protein, is expressed in mammalian cells in two isoforms: AnxA6-1 and AnxA6-2, the latter lacking the 524- VAAEIL-529 sequence at the start of repeat 7 ... [more ▼]

Annexin A6 (AnxA6), a calcium- and membrane-binding protein, is expressed in mammalian cells in two isoforms: AnxA6-1 and AnxA6-2, the latter lacking the 524- VAAEIL-529 sequence at the start of repeat 7. The different intracellular localization of these two isoforms suggests distinct function in membrane dynamics. The aim of this work was to analyze the behavior of AnxA6 isoforms at the air/water interface alone and in the presence of membrane mimicking lipid monolayers. Using Langmuir technique showed that AnxA6-2 was less adsorbed to the neat air-water interface than AnxA6-1 at acidic pH and minor differences in their PM-IRRAS spectra were observed. Both isoforms exhibited similar behavior towards cholesterol monolayer. However, the interactions of AnxA6-2 with cholesterol ester monolayer were most favorable compared to AnxA6-1. Our experimental data are discussed in relation with the different intracellular localization of the two isoforms and with our constructed model of AnxA6-2 with the known crystal structure of AnxA6-1 showing the persistence of the 516-529 α- helix in AnxA6-2 despite the absence of the 524-VAAEIL-529 sequence. [less ▲]

Physico-chemical and membrane-interacting properties of D-xylose-based bolaforms. Influence of the anomeric configuration

in MATEC Web of Conferences (2013), ACCEPTED

Sugar-based biosurfactants such as xylose-derived bolaforms have interesting properties, for example high biocompatibility and biodegradability which make them potential useful molecules in the ... [more ▼]

Sugar-based biosurfactants such as xylose-derived bolaforms have interesting properties, for example high biocompatibility and biodegradability which make them potential useful molecules in the pharmaceutical and cosmetic fields. Until now, no detailed analyses of the physico-chemical properties of these compounds have been undertaken. Two symmetrical D-xylose-based bolaforms were chemically synthesized where the two xylose heads are linked via an acetal link to a hydrocarbon chain containing 18 carbon atoms and an unsaturation. The two bolaforms differ only by their anomeric configuration: or The bolaform exhibits interfacial properties at the air-water interface which is not the case for the . FTIR spectroscopy showed that the interactions between the bolaform and POPC, a model phospholipid, involve the carbonyl groups of the phospholipid [less ▲]

Molecular analysis of the interfacial and membrane-interacting properties of D-xylose-based bolaforms

Poster (2012, October)

Biophysical Approaches Modelling the Interaction of the Antimicrobial Mycosubtilin with Sterol‐Containing Membranes of Sensitive Cells

Poster (2012, July)

Calcium-induced conformational changes of the elicitor and membrane-active fengycin

Poster (2012, April)

Fengycin is a natural lipopeptide synthetized by Bacillus subtilis strains. It is characterized by strong antifungal and low hemolytic activities. It seems also play a role in the promoting of elicitor ... [more ▼]

Fengycin is a natural lipopeptide synthetized by Bacillus subtilis strains. It is characterized by strong antifungal and low hemolytic activities. It seems also play a role in the promoting of elicitor activities of other compounds. The target of the biological activities of fengycin is supposed to be plasma membrane of sensitive cells. Even though the natural fengycin from has been discovered 25 years ago, nowadays, there is an increase of interest for this compound because of its potent applications. Until 15 years ago, the primary structure of fengycin was a matter of open debate before the publication of the corrected structure obtained by nuclear magnetic resonance and mass spectroscopy techniques. Although the infrared and ultraviolet absorption spectra of the lipopeptide were measured, no detailed analysis of these data was performed probably because of the unconventional sequence of the lipopeptide making these kinds of analyses complicated. In this work, our attempt was to analyze the conformational properties of fengycin as well as the calcium-induced changes using two complementary spectroscopic methods, Fourrier transformed infrared spectroscopy (FTIR) and circular dichroism (CD). In a first step, we have characterized the conformational properties of pure fengycin. The lipopeptide adopts turn conformation in trifluoroethanol, a membrane-mimicking solvent. D-aminoacids seem to be involved in intra molecular hydrogen bonds. In a second step, we have investigated the role played by Ca2+ ions on the possible conformational changes of fengycin. The addition of calcium gives rise to important modifications of the conformation. As fengycin has two glutamate residues, calcium is supposed to bind to their side chains. In conclusion, we have demonstrated that the conformation of fengycin is closely depending of the environment and the presence of calcium ions play an important role on the conformational changes of the lipopeptide. Moreover, spectra obtained both FTIR and CD methods ascertain the presence of turn conformation. [less ▲]

Techniques spectroscopiques pour comprendre les interactions entre des molécules biologiques et des modèles membranaires

Scientific conference (2012, March)

De nombreux processus biochimiques impliquent une interaction entre la membrane plasmique et une molécule agissant sur celle-ci. Les peptides antimicrobiens constituent un bel exemple pour les molécules ... [more ▼]

De nombreux processus biochimiques impliquent une interaction entre la membrane plasmique et une molécule agissant sur celle-ci. Les peptides antimicrobiens constituent un bel exemple pour les molécules actives sur la membrane. Notre but est de comprendre les interactions de ces peptides avec la membrane plasmique de leurs cellules cibles. En raison de la complexité de la membrane rendant difficile la compréhension de ces processus, nous avons recours à des systèmes plus simples appelée modèles membranaires. Les modèles membranaires sont donc analysés en absence et en présence des peptides antimicrobiens par différentes techniques spectroscopiques afin d’obtenir des informations à l’échelle moléculaire. La présentation revisite ces techniques d’analyse en mettant en évidence leurs potentialités [less ▲]

Second harmonic generation to monitor the interactions of the antimicrobial mycosubtilin with membrane-mimicking interfacial monolayers

in BioNanoScience (2012), 2(2), 108-112

Mycosubtilin is a strong antimicrobial agent belonging to the iturinic lipopeptide family which contains a single tyrosine residue. Its cell target has been shown to be the cytoplasmic membrane. This ... [more ▼]

Mycosubtilin is a strong antimicrobial agent belonging to the iturinic lipopeptide family which contains a single tyrosine residue. Its cell target has been shown to be the cytoplasmic membrane. This tyrosine residue has been previously shown to be essential for the biological activity of mycosubtilin. Since we have previously demonstrated that tyrosine, an aromatic amino acid, can be used as an endogenous probe for the frequency doubling process, the presence of a tyrosine residue in mycosubtilin allowed us to investigate the interactions of mycosubtilin with biomimetic lipid monolayers at the air–water interface by second harmonic generation (SHG). Mycosubtilin was added underneath dipalmitoylphosphatidylcholine or cholesterol monolayers at the air–water interface and significant increases in the surface pressure were observed in both cases. This observation demonstrates that mycosubtilin interacts with these biomimetic membranes. A light polarization resolved analysis of the SHG signals recovered for these two systems was then performed and confirmed that those interactions between the tyrosine residue in mycosubtilin and the membranes could be monitored by SHG. Furthermore, the differences exhibited by the nonlinear optical measurements for different membranes showed that these interactions depend on the nature of the biomimetic membrane present at the air–water interface. [less ▲]

Annexins as organizers of cholesterol- and sphingomyelin-enriched membrane microdomains in Niemann-Pick type C disease.

in Cellular and Molecular Life Sciences : CMLS (2011), 69(11), 1773-1785

Growing evidence suggests that membrane microdomains enriched in cholesterol and sphingomyelin are sites for numerous cellular processes, including signaling, vesicular transport, interaction with ... [more ▼]

Growing evidence suggests that membrane microdomains enriched in cholesterol and sphingomyelin are sites for numerous cellular processes, including signaling, vesicular transport, interaction with pathogens, and viral infection, etc. Recently some members of the annexin family of conserved calcium and membrane-binding proteins have been recognized as cholesterol-interacting molecules and suggested to play a role in the formation, stabilization, and dynamics of membrane microdomains to affect membrane lateral organization and to attract other proteins and signaling molecules onto their territory. Furthermore, annexins were implicated in the interactions between cytosolic and membrane molecules, in the turnover and storage of cholesterol and in various signaling pathways. In this review, we focus on the mechanisms of interaction of annexins with lipid microdomains and the role of annexins in membrane microdomains dynamics including possible participation of the domain-associated forms of annexins in the etiology of human lysosomal storage disease called Niemann-Pick type C disease, related to the abnormal storage of cholesterol in the lysosome-like intracellular compartment. The involvement of annexins and cholesterol/sphingomyelin-enriched membrane microdomains in other pathologies including cardiac dysfunctions, neurodegenerative diseases, obesity, diabetes mellitus, and cancer is likely, but is not supported by substantial experimental observations, and therefore awaits further clarification. [less ▲]

Second harmonic generation as a tool to probe the interactions of peptides with membrane-mimicking interfacial monolayers

Conference (2011)