| Abstract
| - The interaction of the three main components of the mitochondrial membrane, namely cardiolipin,phosphatidylcholine, and phosphatidylethanolamine, has been studied investigating mixed cardiolipin−phosphatidylcholine and cardiolipin−phosphatidylethanolamine monolayers at different cardiolipin molarfractions. The thermodynamic behavior of the mixed monolayers was investigated by means of surface pressureand surface potential measurements, and atomic force microscopy was employed to characterize the morphologyof the monolayers. Langmuir isotherms and surface potential curves show a regular behavior with a progressivetransition toward the isotherm of the pure component. Positive deviations from ideality in the excess Gibbsenergies of mixing suggest the presence of repulsive interactions in both systems. Analysis of partial moleculardipole moment indicates a discontinuity at a definite cardiolipin/phosphatidylethanolamine molar fraction,suggesting the formation of a stoichiometric complex; as a consequence, in mixed cardiolipin−phosphatidylethanolamine monolayers, a phase separation is observed at phosphatidylethanolamine excess. AFMmeasurements indicate the presence of two domains: one made by phosphatidylethanolamine and the otherby a regular arrangement of phosphatidylethanolamine and cardiolipin at a fixed molecular ratio.
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