Role of guanidinium group in the insertion of l-arginine in DMPE and DMPC lipid interphases

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.