Influence of Lipid Chemistry on the Osmotic Response of Cell Membranes: Effect of Non-Bilayer Forming Lipids

The cell membrane can withstand significant osmotic stress before pores open to relieve the tension. The amount of stress that the membrane can withstand is determined by the lipid chemistry; we have examined the effect of four non-bilayer forming lipids on the stability of phosphatidylcholine (PC, a bilayer forming lipid) membranes. Large unilamellar vesicles were subjected to hypo-osmotic gradients and the leakage of their contents was quantified. Three micelle forming lipids, lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), and lysophosphatidylglycerol (LPG), were studied along with one inverted-micelle forming lipid, phosphatidylethanolamine (PE). The inclusion of the lyso lipids resulted in greater leakage from the vesicles, while the inclusion of the PE resulted in less leakage from the vesicles. From the leakage data, the pressure difference at the point of pore closure was determined along with the critical surface tension and the line tension. Results will be presented detailing how the shape and percentage of non-bilayer forming lipids affects leakage.