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Surfactant-like membranes containing the 21-residue peptide KLLLL-KLLLLKLLLLKLLLLK (KL4 ), have been clinically tested as a therapeu-tic agent for respiratory distress syndrome in premature infants. The aims of this study were to investigate the interactions between the KL4 peptide and lipid bilayers, and the role of both the lipid composition and KL4 structure on the surface adsorption activity of KL4 -containing membranes. | ềFEBS Journal Physical properties and surface activity of surfactant-like membranes containing the cationic and hydrophobic peptide KL4 Alejandra Saenz1 Olga Canadas1 Luis A. Bagatolli2 Mark E. Johnson3 and Cristina Casals1 1 Department of Biochemistry and Molecular Biology I Complutense University of Madrid Spain 2 MEMPHYS-Center for Biomembrane Physics Department of Biochemistry and Molecular Biology University of Southern Denmark Odense Denmark 3 Discovery Laboratories Mountain View CA USA Keywords differential scanning calorimetry DPH fluorescence GUV lung surfactant surface adsorption Correspondence C. Casals Department of Biochemistry and Molecular Biology I Faculty of Biology Complutense University of Madrid 28040 Madrid Spain Fax 34 91 3944672 Tel 34 91 3944261 E-mail ccasalsc@bio.ucm.es These authors contributed equally to this study Received 5 March 2006 revised 31 March 2006 accepted 3 April 2006 doi 10.1111 j.1742-4658.2006.05258.x Surfactant-like membranes containing the 21-residue peptide KLLLL-KLLLLKLLLLKLLLLK KL4 have been clinically tested as a therapeutic agent for respiratory distress syndrome in premature infants. The aims of this study were to investigate the interactions between the KL4 peptide and lipid bilayers and the role of both the lipid composition and KL4 structure on the surface adsorption activity of KL4-containing membranes. We used bilayers of three-component systems 1 2-dipalmitoyl-phosphat-idylcholine 1-palmitoyl-2-oleoyl-phosphatidylglycerol palmitic acid DPPC POPG PA and DPPC 1-palmitoyl-2-oleoyl-phosphatidylcholine POPC PA and binary lipid mixtures of DPPC POPG and DPPC PA to examine the specific interaction of KL4 with POPG and PA. We found that at low peptide concentrations KL4 adopted a predominantly a-helical secondary structure in POPG- or POPC-containing membranes and a b-sheet structure in DPPC PA vesicles. As the concentration of the peptide increased KL4 interconverted to a b-sheet structure in DPPC POPG PA or DPPC .
