ELECTROSTATICS OF LIPID BILAYER BENDING

The electrostatic contribution to spontaneous membrane curvature is ca lculated within Poisson-Boltzmann theory under a variety of assumption s and emphasizing parameters in the physiological range. Asymmetrical surface charges can be fixed with respect to bilayer midplane area or with respect to the lipid-water area, but induce curvatures of opposit e signs. Unequal screening layers on the two sides of a vesicle (e.g., multivalent cationic proteins on one side and monovalent salt on the other) also induce bending. For reasonable parameters, tubules formed by electrostatically induced bending can have radii in the 50-100-nm r ange, often seen in many intracellular organelles. Thus membrane assoc iated proteins may induce curvature and subsequent budding, without th emselves being intrinsically curved, Furthermore, we derive the previo usly unexplored effects of respecting the strict conservation of charg e within the interior of a vesicle. The electrostatic component of the bending modulus is small under most of our conditions and is left as an experimental parameter. The large parameter space of conditions is surveyed in an array of graphs.