Spreading of biomembranes at the air/water interface

This paper presents the compression isotherms obtained by spreading membranes of intestinal brush border, human erythrocyte and Escherichia coli (cytoplasmic) at the air/water interface. Unilamellar membrane films were formed, with a good yield, at zero surface pressure, whereas multilamellar structures were formed at high surface pressure. Once formed, the films were particularly stable and could be manipulated without any detectable loss. With doubly-labelled E. coli cytoplasmic membrane, we could show that phospholipids and proteins spread, with the same yield, as a single unit. Moreover, we studied the influence of hydrolytic enzymes, chemical agents and cations on the compression isotherm of biomembranes. The resultant changes in architecture of membrane films can provide a very simple method of studying the influence of membrane packing on catalytic activity and protein conformation of membrane-bound proteins.