Water Permeability across the Droplet Bilayer Reveals Interaction between Cholesterol and Polyunsaturated Lipids

Abstract

Cholesterol can be the major component of total lipid in mammalian cellular membranes, hence the knowledge of its association with lipid bilayer membranes will be essential to understanding membrane structure and function. A Droplet Interface Bilayer (DIB) provides a convenient and reliable platform through which permeability coefficient and activation energy for water transport across the membrane can be determined. In this paper, we present the effect of acyl chain structure in amphiphilic monoglycerides in the presence and absence of cholesterol on the permeability of water across DIB membranes composed of these monoglycerides, where the acyl chain length, number of double bonds, and the position of double bond are varied systematically along the acyl chains, at two different cholesterol concentrations. Our systematic studies show dramatic sensitivity and selectivity of specific interaction of cholesterol with the monoglyceride bilayer having structural variations in acyl chain compositions. Our findings allow us to delineate the exquisite interplay between membrane properties and structural components and understand the balanced contribution of each. This successful demonstration will provide important insights into the factors determinative of passive membrane permeability in a wide variety of biologically relevant systems.