Effect of Lipid Headgroups and (Nonelectrolyte) Solution on the Structural and Phase Properties of Bilayer Membranes

Abstract

AbstractProperties of the biological and model membranes can be regulated by the lipid polar headgroups and their bathing solution. This occurs primarily via changes in the interfacial hydrophilicity and hydration, which are mostly a result of the lipid deprotonation or osmotic dehydration. Steric or electrostatic effects normaly play a minor role. Therefore, phosphate derivatization or protonation, further changes that decrease the lipid capacity for the hydrogen bonding and lower the interfacial affinity for binding water, as well as any system alterations that diminish the amount of interbilayer water can all cause the lipid chain melting phase transition temperature, the persistence of the lamellar lipid phase, and the colloidal stability of vesicle suspension, but also the height of the membrane permeability barrier to decrease, whereas lipid protonation or dealkylation have the reverse effect. – Lipid bilayers and their adjacent solution behave as single thermodynamic entity. Changes in the polar headgroup region and in the solvent composition consequently can regulate not only the membrane capacity for molecular or supramolecular reorganisation (e.g. phase changes or membrane fusion, respectively) but moreover may govern the short‐range intermembrane (e.g. hydration) forces and, to some extent, affect the membrane‐solute interactions. These effects are therefore of considerable interest and relevance for the studies and understanding of membrane binding and transport.