Abstract
The Langmuir monolayers of L-α-phosphatidylcholine from egg yolk were studied by Wilhelmy method. The surface pressure versus molecular area isotherm of lipid on pure water and different subphase (with a presence of divalent ions: Sr2+, Cd2+, Ba2+, Pb2+) was obtained. The limiting area of the isotherms depends on the presence of subphase ions. The addition of divalent ions to the subphase stabilized the monolayers and increased the limiting areas of the monolayer. During the compression in monolayer complexes of 1:1 and 2:1 stoichiometry between L-α-phosphatidylcholine from egg yolk and divalent ions are formed. We used the equilibrium theory to describe the behavior of monolayer components at the air/water interface. An equilibrium theory to describe the behavior of monolayer components at the air/water interface was developed in order to obtain the stability constants and area occupied by one molecule of LMe2+ or L2Me2+ complexes, and complex formation energy (Gibbs free energy) values. These mathematically derived and experimentally confirmed values are of great importance for the interpretation of phenomena occurring in lipid monolayers and bilayers.
Highlights
IntroductionResearchers have used Langmuir films as model systems of biological membranes [1]
For many years, researchers have used Langmuir films as model systems of biological membranes [1]
We present surface tension measurements of L-α-phosphatidylcholine from egg yolk monolayers obtained using a Langmuir method as a function of divalent M e2+ ion concentration
Summary
Researchers have used Langmuir films as model systems of biological membranes [1]. Amphiphilic monolayers (surface films formed at the air/water interface) are useful for studying mechanisms of biophysical and biochemical phenomena in living cells. These monolayers can provide important knowledge regarding the properties of thin amphiphilic arrangements (e.g., fatty acids, lipids, proteins, and mixed films) in agricultural, pharmaceutical, and food-science applications [2, 3]. L-α-Phosphatidylcholine from egg yolk (Fig. 1) monolayer models have been used to reconstruct various biophysical processes in biological membranes [2, 3, 5,6,7,8] Physicochemical properties of these monolayers depend on the three-dimensional structures of lipid molecules, their packing density at the interface, the pH of the subphase, and its ionic composition and concentration [3, 5]. Many interesting information on monolayers is provided by Chifu’s group studies about thermodynamics of equilibria in monolayers at various surface pressures, including the collapse pressure [23, 24]
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