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Bouchet A.M.,Free University of Colombia | Bouchet A.M.,Laboratorio Of Fisicoquimica Of Membranas Lipidicas | Lairion F.,Laboratorio Of Fisicoquimica Of Membranas Lipidicas | Ruysschaert J.-M.,Free University of Colombia | Lensink M.F.,Lille University of Science and Technology
Chemistry and Physics of Lipids

Arginine-rich peptides receive increased attention due to their capacity to cross different types of membranes and to transport cargo molecules inside cells. Even though peptide-induced destabilization has been investigated extensively, little is known about the peptide side-chain and backbone orientation with respect to the bilayer that may contribute to a molecular understanding of the peptide-induced membrane perturbations. The main objective of this work is to provide a detailed description of the orientation of arginine peptides in the lipid bilayer of PC and negatively charged PG liposomes using ATR-IR spectroscopy and molecular modeling, and to relate these orientational preferences to lipid bilayer destabilization. Molecular modeling showed that above the transition temperature arginine side-chains are preferentially solvent-directed at the PC/water interface whereas several arginine side-chains are pointing towards the PG hydrophobic core. IR dichroic spectra confirmed the orientation of the arginine side chains perpendicular to the lipid-water interface. IR spectra shows an randomly distributed backbone that seems essential to optimize interactions with the lipid membrane. The observed increase of permeation to a fluorescent dye is related to the peptide induced-formation of gauche bonds in the acyl chains. In the absence of hydrophobic residues, insertion of side-chains that favors phosphate/guanidium interaction is another mechanism of membrane permeabilization that has not been further analyzed so far. © 2011 Elsevier Ireland Ltd. Source

Bouchet A.,Laboratorio Of Fisicoquimica Of Membranas Lipidicas | Lairion F.,Laboratorio Of Fisicoquimica Of Membranas Lipidicas | Disalvo E.A.,Laboratorio Of Fisicoquimica Of Membranas Lipidicas
Biochimica et Biophysica Acta - Biomembranes

l-Arginine (Arg) is a positively charged amino acid constituent of peptides and proteins, participating in diverse mechanisms of protein-membrane interaction. The effect of Arg on phosphatidylcholine (PC) membranes has been previously related to water structure changes and to the presence of water defects in the hydrocarbon region. However, no information is available with regard to phosphatidylethanolamine (PE), another important component of lipid membranes. For this reason, the aim of this study is to determine the effect of Arg on DMPE membranes and partially methylated PEs in comparison to DMPC. The adsorption of the amino acid onto the lipid membranes was followed by determining the changes in the surface potential as a function of the bulk amino acid concentrations. The effects of Arg on the surface properties were also measured by changes in the surface pressure and the dipole potential. The onset of the transition temperature was measured with a fluorophore anchored at the membrane interphase. The results provide a new insight on amino acid-PE interactions, which can be ascribed to specific perturbations in the head group region induced by the guanidinium residue. © 2009 Elsevier B.V. All rights reserved. Source

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