Shape Transitions in Anisotropic Multicomponent Lipid Tubules

Ternary mixtures of saturated and unsaturated lipids together with cholesterol can be induced to phase separate by photo-peroxidation into lipid-ordered (lo) and lipiddisordered (ld) domains. Because these have different mechanical properties, the phase separation is accompanied by dramatic changes in morphology. This work considers a tubule composed of ld phase with lo phase inclusions that possess greater rigidity; this system has been shown experimentally by Yuan and coworkers to spontaneously adopt either banded or disk configurations following phase separation. The static behavior of inter-domain interactions is analyzed in each of these geometries by solving the linearized shape equations. These calculations suggest a possible mechanism by which the two structures form.