Abstract
Basic understanding of the barrier properties of biological membranes can be obtained by studying model systems, such as planar lipid bilayers. Here, we study water pores in planar lipid bilayers in the presence of transmembrane voltage. Planar lipid bilayers were exposed to fast and slow linearly increasing voltage and current signals. We measured the capacitance, breakdown voltage, and rupture time of planar lipid bilayers composed of 1-pamitoyl 2-oleoyl phosphatidylcholine (POPC), 1-pamitoyl 2-oleoyl phosphatidylserine (POPS), and a mixture of both lipids in a 1:1 ratio. Based on the measurements, we evaluated the change in the capacitance of the planar lipid bilayer corresponding to water pores, the radius of water pores at membrane rupture, and the fraction of the area of the planar lipid bilayer occupied by water pores.planar lipid bilayer capacitance, which corresponds to water pores, water pore radius at the membrane rupture, and a fraction of the planar lipid bilayer area occupied by water pores. The estimated pore radii determining the rupture of the planar lipid bilayer upon fast build-up of transmembrane voltage are 0.101 nm, 0.110 nm, and 0.106 nm for membranes composed of POPC, POPS, and POPC:POPS, respectively. The fraction of the surface occupied by water pores at the moment of rupture of the planar lipid bilayer The fraction of an area that is occupied by water pores at the moment of planar lipid bilayer rupture is in the range of 0.1–1.8%.
Highlights
Biological membranes, the barriers that envelope the cell and its inner organelles, play an important role in the physiology and functionality of cells
Planar lipid bilayers were exposed to linearly rising voltage and current signals of various slopes to examine Ubr, the change in C at tbr and the fraction of the planar lipid bilayer occupied by water pores close to the membrane rupture
Theories of pore formation and molecular dynamics simulations suggest recurrent hydrophobic pores or water pores whose occurrence is strongly dependent on the electric field
Summary
Biological membranes, the barriers that envelope the cell and its inner organelles, play an important role in the physiology and functionality of cells. Biological membranes are composed of lipids, proteins, and small amounts of carbohydrates, the barrier function is assured by the thin lipid bilayer. The simplest model of a cell membrane patch is a planar lipid bilayer. To mimic a non-curved fragment of the cell membrane, the planar lipid bilayer should separate two electrolytes. The planar lipid bilayer is usually vertically formed across a small aperture in a hydrophobic partition that separates two compartments filled with electrolytes [1]. Electrodes immersed in the electrolyte permit measurements of electric parameters of the planar lipid bilayer. Voltage-controlled and current-controlled methods enable observing electrical properties of the planar lipid bilayer and its structural changes that are reflected in the electrical characteristics [4,5,6,7]
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