Theory of self-assembled tubules and helical ribbons

Many types of amphiphilic molecules self-assemble in solution to form cylin drical tubules and helical ribbons. Some examples include diacetylenic lipi ds, amide amphiphiles, bile, and diblock copolymers. Researchers have propo sed a variety of models to explain the formation of these high-curvature st ructures. These models can be divided into two broad categories: models bas ed on the chiral elastic properties of membranes, and models based on other effects, including electrostatic interactions, elasticity of orientational order, and spontaneous curvature. In this paper, we review the range of th eoretical approaches and compare them with relevant experiments. We argue t hat the category of models based on chiral elastic properties provides the most likely explanation of current experimental results, and we propose fur ther theoretical and experimental research to give a more detailed test of these models.