Effect of tension and curvature on the chemical potential of lipids in lipid aggregates

Abstract

Understanding the factors that influence the free energy of lipids in bilayer membranes is an essential step toward understanding exchange processes of lipids between membranes. In general, both lipid composition and membrane geometry can affect lipid exchange rates between bilayer membranes. Here, the free energy change ΔG_des for the desorption of dipalmitoyl-phosphatidylcholine (DPPC) lipids from different lipid aggregates has been computed using molecular dynamics simulations and umbrella sampling. The value of ΔG_des is found to depend strongly on the local properties of the aggregate, in that both tension and curvature lead to an increase in ΔG_des. A detailed analysis shows that the increased desorption free energy for tense bilayers arises from the increased conformational entropy of the lipid tails, which reduces the favorable component −TΔS_L of the desorption free energy.