Membrane stability is of vital importance to cells. When subjected to strong stimuli, such as electric pulses, pores open in the membrane. Usually, pores reseal and membrane integrity is restored, as observed in neutral PC (phosphatidylcholine) giant unilamellar vesicles (GUVs). However, GUVs containing charged lipids may display a different response to strong DC electric pulses: Some micron-sized pores open indefinitely leading to vesicle burst while GUVs that apparently restore their integrity after macropore closure can exhibit a long-lasting high permeability revealing the persistence of sub-microscopic pores minutes after the end of the pulse. Here, the stability of GUVs composed of PC and increasing fractions of other physiologically relevant anionic lipids, such as cardiolipin (CL), phosphatidylinositol (PI) and phosphatidylinositol 4,5-bisphosphate (PIP2), is investigated with phase contrast optical microscopy. First, the occurrence frequency of disturbing events is quantified in a large population of GUVs. Then, the dynamics of vesicle contrast loss due to long-lasting permeability is assessed on individual GUVs. Finally, the pore edge tension, which reflects the energy penalty per unit length to arrange lipids in the pore rims, is measured from the dynamics of macropore closure following a previously developed method. Overall, membranes containing higher fractions of charged lipids are more unstable and prone to disturbances, as a result of a reduced pore edge tension. More specifically, the membrane edge tension decreased significantly for membranes containing 50% of anionic lipid.

Stability of membranes containing different types of anionic lipids

ACS Spring Meeting 2021

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