Effect of lysozyme subphase and insertion on several lipid films

Abstract

The influence of proteins on lipid monolayers is a subject of biological interest. In this work the influence of lysozyme on lipid films of stearic acid, oleic acid, cholesterol, DPPC and POPC has been studied. The Langmuir monolayer technique, using surface pressure-area isotherms and elastic modulus plots, as well as protein insertion experiments in lipid monolayers, have been used. Results indicate that lysozyme affects the lipid monolayer formation, the elastic modulus and, sometimes, the physical state of the monolayer. This influence is more important till moderate surface pressures. At high surface pressures and near the physiological value of lateral pressure of 33 mN/m, there is expulsion of lysozyme out of the monolayer. This expulsion is more important for stearic acid, DPPC and POPC. The lower value of maximum insertion pressure is for stearic acid and the higher one is for oleic acid. The relation between the initial and the increased surface pressure in insertion experiments has been analysed