Symmetries Broken by Electrostatics in Nanoscale Ionic Assemblies

Electrostatic interactions are essential in the structure and function of biological assemblies since most biomolecules are charged. Oppositely charged molecules often co-assemble into units with some inherent asymmetry that renders functionality. Symmetric electrostatic interactions alone are shown to spontaneously break symmetries at the nanometer scale, such as the formation of helical ionic patterns on fibers and the buckling of ionic shells into icosahedra. Through varying the strength of the electrostatic interactions we control the pitch of the helical patterns of the surface of virus-like fibers or of aqueous channels. In ionic spheres, correlations may lead to faceting into icosahedra without rotational symmetry. This buckling appears on vesicles of cationic-anionic molecules, as well as on co-adsorbed charged molecules that form ionic rafts.

Monica Olvera de la Cruz, Northwestern University

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