Photoregulated “Breathing” Vesicle with Inversed Supramolecular Chirality

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.