Flexo-electricity in Membranes

Lipids contain electrical dipoles in their headgroups. In the figure below, the dipoles are further apart in the upper monolayer than the lower monolayer when the membrane is curved. The differential dipole density induces a net polarization and consequently a transmembrane electrical potential. This phenomenon is formally defined as the flexo-electric effect, first envisioned for liquid crystals. The reverse effect is equally compelling: a membrane will bend in response to an applied transmembrane electrical potential. Thus, curvature and electrical potential are strongly coupled in lipid systems.


Electric Fields and Curvature in Cellular and Model Membranes: Living cells are electrically negative on the inside, and an electrical potential of nearly -70 mV, equivalent to a field of 15 million V/m, is maintained across the cell membrane. In neurons, the potential can increase to values an order of magnitude bigger during the transmission of the action potential. We investigate if such potentials can induce functionally relevant curvature changes in model membranes. Membrane curvature has a well-recognized role to play in key cellular processes such as vesicle budding, membrane fusion, protein sorting and enzyme activation . Curvature and membrane tension can also affect the activity of mechanosensitive ion channels that are also sensitive to membrane potential. The relationship between membrane curvature and electric potential thus affects a range of vital cellular processes. Model lipid bilayer systems, which comprise pure or mixed lipid bilayers, are also obliged to be sensitive to the flexoelectric effect.

Relevant Publications

Bruhn, D. S., Lomholt, M. A., and Khandelia, H. (2016) Quantifying the Relationship between Curvature and Electric Potential in Lipid Bilayers, J Phys Chem B 120, 4812-4817