Lipid-mediated interactions between intrinsic molecules in bilayer membranes

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Abstract
The effect of intrinsic molecules (impurities) dissolved in phospholipid bilayers on their lipid enviroment and the related lipid-mediated interactions between such molecules are examined in terms of a ten-state model for lipid chain configurations and interchain interactions. The numerical parameters used in the calculations were previously obtained by fitting to experimental data. Numerical results are presented for the case when the impurity is a cholesterol molecule, a protein, or a vacancy and when the lipid bilayer is either in the gel or fluid (liquids crystal) phase. The calculations indicate that proteins fluidize their lipid environment when the bilayer is in the gel phase. The resulting lipid-mediated interaction is shown to be short range and to have a different behavior below and above the main gel–fluid phase transition. The relation to previous theories is discussed in the final section.