Regions of Correlated Fluctuations in Membrane Lipid Concentrations as a Consequence of Charged Cytoplasmic Lipids

Abstract

The cytoplasmic leaflet of the mammalian plasma membrane is characterized by charged lipids such as phosphatidylserine and phosphatidylinositol and its phosphorylated derivatives PIP and PIP2. Their concentrations vary from about ten to less than one percent. The charges are balanced by counter ions in the cytosol. As a consequence there are electric dipole moments in the cytoplasmic leaflet. The extra-cellular leaflet has essentially no charged lipids. In contrast to the electric dipole moments of the lipid head groups in both leaves which, due to their opposite orientation, essentially cancel one another at large distances, the dipole moments of the charged lipids in the cytoplasmic leaf interact via a long-ranged force.