Isothermal titration calorimetry studies of the interaction of surfactin analogues with a model membrane

Poster (2008)

Atomic force microscopy of supported lipid bilayers.

in Nature Protocols (2008), 3(10), 1654-9

Supported lipid bilayers (SLBs) are widely used in biophysical research to investigate the properties of biological membranes and offer exciting prospects in nanobiotechnology. Atomic force microscopy ... [more ▼]

Supported lipid bilayers (SLBs) are widely used in biophysical research to investigate the properties of biological membranes and offer exciting prospects in nanobiotechnology. Atomic force microscopy (AFM) has become a well-established technique for imaging SLBs at nanometer resolution. A unique feature of AFM is its ability to monitor dynamic processes, such as the interaction of bilayers with proteins and drugs. Here, we present protocols for preparing dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DOPC/DPPC) bilayers supported on mica using small unilamellar vesicles and for imaging their nanoscale interaction with the antibiotic azithromycin using AFM. The entire protocol can be completed in 10 h. [less ▲]

Characterization of the interactions between fluoroquinolone antibiotics and lipids: a multitechnique approach.

in Biophysical Journal (2008), 94(8), 3035-46

Probing drug/lipid interactions at the molecular level represents an important challenge in pharmaceutical research and membrane biophysics. Previous studies showed differences in accumulation and ... [more ▼]

Probing drug/lipid interactions at the molecular level represents an important challenge in pharmaceutical research and membrane biophysics. Previous studies showed differences in accumulation and intracellular activity between two fluoroquinolones, ciprofloxacin and moxifloxacin, that may actually result from their differential susceptibility to efflux by the ciprofloxacin transporter. In view of the critical role of lipids for the drug cellular uptake and differences observed for the two closely related fluoroquinolones, we investigated the interactions of these two antibiotics with lipids, using an array of complementary techniques. Moxifloxacin induced, to a greater extent than ciprofloxacin, an erosion of the DPPC domains in the DOPC fluid phase (atomic force microscopy) and a shift of the surface pressure-area isotherms of DOPC/DPPC/fluoroquinolone monolayer toward lower area per molecule (Langmuir studies). These effects are related to a lower propensity of moxifloxacin to be released from lipid to aqueous phase (determined by phase transfer studies and conformational analysis) and a marked decrease of all-trans conformation of acyl-lipid chains of DPPC (determined by ATR-FTIR) without increase of lipid disorder and change in the tilt between the normal and the germanium surface (also determined by ATR-FTIR). All together, differences of ciprofloxacin as compared to moxifloxacin in their interactions with lipids could explain differences in their cellular accumulation and susceptibility to efflux transporters. [less ▲]

Probing Peptide-Membrane Interactions Using Afm

in Surface and Interface Analysis [=SIA] (2008), 40(3-4), 151-156

Atomic force microscopy (AFM) has become a powerful addition to the range of instruments available to probe the organization of lipid monolayers and bilayers. Currently, AFM is the only tool that can ... [more ▼]

Atomic force microscopy (AFM) has become a powerful addition to the range of instruments available to probe the organization of lipid monolayers and bilayers. Currently, AFM is the only tool that can provide nanoscale topographic images of supported lipid membranes under physiological conditions, enabling researchers to resolve their detailed structure and to monitor their interaction with drugs, peptides and proteins. Here, we survey recent data obtained by our research groups that demonstrate the power of the technique for exploring peptide–membrane interactions, with an emphasis on microbial lipopeptides and on tilted peptides. [less ▲]

La chimie au service de la biomasse

Scientific conference (2007)

The Biologically Important Surfactin Lipopeptide Induces Nanoripples In Supported Lipid Bilayers

in Langmuir (2007), 23(19), 9769-72

Under specific conditions, lipid membranes form ripple phases with intriguing nanoscale undulations. Here, we show using in situ atomic force microscopy (AFM) that the biologically important surfactin ... [more ▼]

Under specific conditions, lipid membranes form ripple phases with intriguing nanoscale undulations. Here, we show using in situ atomic force microscopy (AFM) that the biologically important surfactin lipopeptide induces nanoripples of 30 nm periodicity in dipalmitoyl phosphatidylcholine (DPPC) bilayers at 25 degrees (i.e. well below the pretransition temperature of DPPC). Whereas most undulations formed the classical straight orientation with characteristic angle changes of 120 degrees , some of them also displayed unusual circular orientations. Strikingly, ripple structures were formed at 15% surfactin but were rarely or never observed at 5 and 30% surfactin, emphasizing the important role played by the surfactin concentration. Theoretical simulations corroborated the AFM data by revealing the formation of stable surfactin/lipid assemblies with positive curvature. [less ▲]

Investigation of interactions between phospholipids, cholesterol and surfactin by atomic force microscopy and differential scanning calorimetry

Poster (2006)

Effects of surfactin produced by Bacillus subtilis on a viral fusion peptide

Poster (2006)

Penetration of surfactin into phospholipid monolayers: Nanoscale interfacial organization

in Langmuir (2006), 22(26), 11337-11345

Atomic force microscopy (AFM) combined with surface pressure-area isotherms were used to probe the interfacial behavior of phospholipid monolayers following penetration of surfactin, a cyclic lipopeptide ... [more ▼]

Atomic force microscopy (AFM) combined with surface pressure-area isotherms were used to probe the interfacial behavior of phospholipid monolayers following penetration of surfactin, a cyclic lipopeptide produced by Bacillus subtilis strains. Prior to penetration experiments, interfacial behavior of different surfactin molecules (cyclic surfactins with three different aliphatic chain lengths-S13, S14, and S15-and a linear surfactin obtained by chemical cleavage of the cycle of the surfactin S15) has been investigated. A more hydrophobic aliphatic chain induces greater surface-active properties of the lipopeptide. The opening of the peptide ring reduces the surface activity. The effect of phospholipid acyl chain length (dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine- (DPPC), and distearoylphosphatidylcholine) and phospholipid polar head (DPPC, dipalmitoylphosphatidylethanolamine and dipalmitoylphosphatidylserine) on monolayer penetration properties of the surfactin S15 has been explored. Results showed that while the lipid monolayer thickness and the presence of electrostatic repulsions from the interfacial film do not significantly influence surfactin insertion, these parameters strongly modulate the ability of the surfactin to alter the nanoscale organization of the lipid films. We also probed the effect of surfactin structure (influence of the aliphatic chain length and of the cyclic structure of the peptide ring) on the behavior of DPPC monolayers. AFM images and isotherms showed that surfactin penetration is promoted by longer lipopeptide chain length and a cyclic polar head. This indicates that hydrophobic interactions are of main importance for the penetration power of surfactin molecules. [less ▲]

Hemolytic activity of new linear surfactin analogs in relation to their physico-chemical properties

in Biochimica et Biophysica Acta - General Subjects (2005), 1726

New linear analogs of surfactin have been synthesized. Their physico-chemical parameters were determined. The results indicate that these linear products show surface activities although they are lowered ... [more ▼]

New linear analogs of surfactin have been synthesized. Their physico-chemical parameters were determined. The results indicate that these linear products show surface activities although they are lowered compared to those of cyclic compounds. The hemolytic activities have also been assayed. In contrast with cyclic surfactins, no significant hemolysis occurs for the linear products in the range of concentrations tested. Moreover, a protective effect against Triton X-100 induced hemolysis has been highlighted for linear surfactins. The concentration at which this protective effect happens is correlated directly to the CMC, and inversely to the acyl chain length of the product. In a hypotonic medium, analogs having a long acyl chain tend to increase the hemolysis, meanwhile the product with the shortest chain tends to decrease it. [less ▲]