Studying the Permeability of Lipid Membranes

Abstract

Lipid molecules contribute to about 50% of the cell structure of a cell. Along with membrane proteins, these molecules have a significant role in transporting substances in and out of the cell. Lipid (phospholipid) molecules are arranged in two layers (a bilayer) given their special properties and act as a lipid bilayer protector for the cell. Proteins transport ions and sugars in and out in cases needed, and two lipid layers prevent excessive entry and exit of these substances. However, some of these substances and particles cannot be passed on by proteins, yet the two lipid layers do the specific processes of this. Firstly, the spherical lipid bilayer membrane was made of phospholipid molecules in the study. These artificial membranes are called a vesicle. Their diameter ranges from a few tens of nanometers to a few tens of micrometers. Holes of several hundred nanometers are used in processes like drug delivery in the body. A few tens of microns model is considered a good one for cell membranes. Vesicles can behave similarly to the lipid portion of a cell membrane. After the production of vesicles, by applying electric potential and creating a pore, they became permeable to ions. Using an experimental arrangement and taking into account the electrophysiological conditions of ionic current passing through the vesiclehole and the value of its permeability time was measured and by converting this ionic current to electrical potential, the value of membrane potential was measured. It was then seen that the electrical potential of the membrane and the time that the membrane remains permeable increase with the increase in ion concentration. With this measurement, information was obtained about the permeability behavior and the value of membrane changes at various ion concentrations.