Effects of passive phospholipid flip-flop and asymmetric external fields on bilayer phase equilibria

Abstract

Compositional asymmetry between the leaflets of bilayer membranes modifies their phase behaviour, and is thought to influence other important features such as mechanical properties and protein activity. We address here how phase behaviour is affected by passive phospholipid \textit{flip-flop}, such that the compositional asymmetry is not fixed. We predict transitions from "pre flip-flop" behaviour to a restricted set of phase equilibria that can persist in the presence of passive flip-flop. Surprisingly, such states are not necessarily symmetric. We further account for external symmetry-breaking, such as a preferential substrate interaction, and show how this can stabilise strongly asymmetric equilibrium states. Our theory explains several experimental observations of flip-flop mediated changes in phase behaviour, and shows how domain formation and compositional asymmetry can be controlled in concert, by manipulating passive flip-flop rates and applying external fields.

arXiv commentAs accepted to Biophys. J

References in corpus (5)

• Freezing in Ising Ferromagnets
• Non-equilibrium raft-like membrane domains under continuous recycling
• Undulation instability in a bilayer lipid membrane due to electric field interaction with lipid dipoles
• Nucleation of symmetric domains in the coupled leaflets of a bilayer
• Kinetics of symmetry and asymmetry in a phase-separating bilayer membrane