| Abstract
| - We have investigated the effect of the insertion of a triblock peptide (hydrophobic−hydrophilic−hydrophobic) in a nonionic lamellar phase composed of C12E4, decane, and water, stabilized by bilayerthermal fluctuations. Circular dichroism shows the peptide to be unordered in water, whereas its hydrophilicpart is rigid and organized in an α-helix in the presence of surfactant bilayers. Surface tension measurementsprove that the peptide is located at the hydrophobic−hydrophilic interface. Together with spectrofluorometry,these experiments suggest that the peptide lies on the bilayer surface. The Caillé parameter, η, of thelamellar phase, obtained by SAXS experiments, decreases with peptide concentration. This decrease hasbeen interpreted as an increase of the bilayer effective thickness induced by the peptide and is well fittedby a recent model. The bilayer bending rigidity κ increases linearly with peptide concentration, up to twotimes the rigidity of a bare bilayer with mole ratio of peptide to surfactant as low as 5.2 × 10-4. The smecticcompressibility modulus, B̄, decreases, implying that the peptide presence softens interactions betweenbilayers.
|
