Buckled Membranes in Mixed-Valence Ionic Amphiphile Vesicles Analyzed by X-Ray Scattering*

We demonstrate that charged amphiphilic molecules, including molecules with biological motifs, organize into non-spherical shapes expected for elastic membranes. Specifically, we demonstrate that anionic (-1) water insoluble amphiphiles and cationic amphiphiles (+3) (which form micelles in water), can co- assemble into small buckled vesicles ( J. Am. Chem. Soc., 131, 2030-12031 (2009) ). The strong electrostatic interaction between the +3 and -1 head groups increases the cohesion energy of the amphiphiles and favors the formation of two-dimensional, flat ionic domains on the vesicle surface, resulting in edges and a buckled shape. WAXS measurements confirm the presence of crystalline domains induced by these ionic correlations.