Isoprenoid lipid chains increase membrane resistance to pore formation

Abstract

The process of electroporation of bilayer lipid membranes made of diphytanoylphosphatidylcholine (DPhPC) has been studied. DPhPC combines a polar part typical for lipids of eukaryotic cells and branched isoprenoid chains forming the hydrophobic “tails” of archaea lipids. From the experimental dependence of the average lifetime on the magnitude of the applied transmembrane potential difference we evaluated line tension of the pore edge in DPhPC bilayers (Γ) and the diffusion coefficient of the defect in the space of the pore radii (D). Line tension Γ was 5.5 ± 0.2 pN and diffusion coefficient D, (6 ± 2) × 10−19 m2/s. Comparison of these values with the values typical for eukaryotic lipids suggests that the critical radius of the pore, further growth of which results in an irreversible electrical breakdown of the lipid bilayer, is less in the case of DPhPC than for conventional membranes of phosphatidylcholines, but the probability of the defect emergence and the increase of its radius is also lower for the DPhPC membranes. Apparently, these peculiarities can be accounted for by high hydrophobicity of the branched isoprenoid chains of DPhPC.