The influence of different membrane components on the electrical stability of bilayer lipid membranes.

A good understanding of cell membrane properties is crucial for better controlled and reproducible experiments, particularly for cell electroporation where the mechanism of pore formation is not fully elucidated. In this article we study the influence on that process of several constituents found in natural membranes using bilayer lipid membranes. This is achieved by measuring the electroporation threshold (V(th)) defined as the potential at which pores appear in the membrane. We start from highly stable 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) membranes (V(th) approximately 200 mV), and subsequently add therein other phospholipids, cholesterol and a channel protein. While the phospholipid composition has a slight effect (100 mV<or=V(th)<or=290 mV), cholesterol gives a concentration-dependent effect: a slight stabilization until 5% weight (V(th) approximately 250 mV) followed by a noticeable destabilization (V(th) approximately 100 mV at 20%). Interestingly, the presence of a model protein, alpha-hemolysin, dramatically disfavours membrane poration and V(th) shows a 4-fold increase ( approximately 800 mV) from a protein density in the membrane of 24x10(-3) proteins/microm(2). In general, we find that pore formation is affected by the molecular organization (packing and ordering) in the membrane and by its thickness. We correlate the resulting changes in molecular interactions to theories on pore formation.