Analysis of constant tension-induced rupture of lipid membranes using activation energy

Abstract

The stretching of biomembranes and lipid membranes plays important roles in various physiological and physicochemical phenomena. Here we analyzed the rate constant k_p of constant tension-induced rupture of giant unilamellar vesicles (GUVs) as a function of tension σ using their activation energy U_a. To determine the values of k_p, we applied constant tension to a GUV membrane using the micropipette aspiration method and observed the rupture of GUVs, and then analyzed these data statistically. First, we investigated the temperature dependence of k_p for GUVs of charged lipid membranes composed of negatively charged dioleoylphosphatidylglycerol (DOPG) and electrically neutral dioleoylphosphatidylcholine (DOPC). By analyzing this result, the values of U_a of tension-induced rupture of DOPG/DOPC-GUVs were obtained. U_a decreased with an increase in σ, supporting the classical theory of tension-induced pore formation. The analysis of the relationship between U_a and σ using the theory on the electrostatic interaction effects on the tension-induced rupture of GUVs provided the equation of U_a including electrostatic interaction effects, which well fits the experimental data of the tension dependence of U_a. A constant which does not depend on tension, U₀, was also found to contribute significantly to U_a. The Arrhenius equations for k_p using the equation of U_a and the parameters determined by the above analysis fit well to the experimental data of the tension dependence of k_p for DOPG/DOPC-GUVs as well as for DOPC-GUVs. On the basis of these results, we discussed the possible elementary processes underlying the tension-induced rupture of GUVs of lipid membranes. These results indicate that the Arrhenius equation using the experimentally determined U_a is useful in the analysis of tension-induced rupture of GUVs.