Dipole potentials and spontaneous curvature: membrane properties that could mediate anesthesia

General anesthetics alter both the membrane dipole potential and the membrane spontaneous curvature, two membrane properties that are likely to have a significant effect on membrane protein function. The dipole potential is a large hydrocarbon positive potential that appears to arise from the lipid carbonyl groups and/or water at the membrane-solution interface. Anesthetics reduce the magnitude of the membrane dipole potential at clinical levels of anesthetics, while non-anesthetics do not, and these changes in potential could modulate conformational transitions in membrane proteins that are electrically active. When the membrane distribution of anesthetic versus non anesthetic compounds is examined, anesthetics exhibit a preference for the membrane interface, whereas non-anesthetic compounds reside within the membrane hydrocarbon core. The preferential localization of anesthetics within the interface accounts for their effect on the membrane dipole potential, and may also serve to alter the membrane spontaneous curvature or lateral stress through the bilayer.