Photoregulated "Breathing" Vesicle with Inversed Supramolecular Chirality.

Abstract

Though phospholipids possess chiral centers, their chiral aggregation within bilayer cell membranes has seldom been referred and recognized. Insight into the chirality at higher levels in artificial molecular bilayer assemblies such as vesicles or liposomes is important to better understand biomembrane functions. In this work, we illustrate the fabrication of chiral vesicles with photoresponsive supramolecular chirality and structural transformation property. Cholesterol was conjugated to azobenzene via different spacers, of which molecular chirality underwent transfer to supramolecular level upon aggregation in water. The resultant building block self-assembled into unilamellar vesicles that could respond to light irradiation by showing reversible extension/contraction behavior. Such "breathing" behavior was accompanied with supramolecular chirality inversion from M- to P-handedness, confirmed by the solid-state crystal structure and electronic circular dichroism spectra based on density functional theory. The vesicle membrane behaves as a matrix to accommodate guest molecules via aromatic interactions, which significantly elevated the UV light resistance with respect to the structural and supramolecular chirality transformation. This work offers an unprecedented rational control over supramolecular chirality using photoresponsiveness in vesicular membranes.