Kinetics of light-induced mesophase transitions in azo-benzene amphiphiles containing lyotropic liquid crystals

This study focuses on the kinetics of light-induced mesophase transitions in lyotropic liquid crystals containing a mixture of phospho-lipids and azo-benzene amphiphiles. Lipid membranes organize in a wide range of morphologies, directly influencing their functionality and the efficiency of associated components such as proteins. Transitions between mesophases occur naturally during membrane fusion and can also be triggered by multiple factors, such as pH, salinity, temperature and light. Employing light to isomerize artificial photoswitchable lipids in mixed model membranes containing 1,2-dipalmitoyl-phos-pha-tidylcholine or 1,2-didecanoyl-phosphatidylcholine revealed light-induced structural changes including mesophase transitions from a lamellar to a cubic Pn3m phase. Performing time-resolved small-angle X-ray scattering measurements, the kinetics of the change in membrane repeat distance and the transition from a lamellar to a bicontinuous cubic phase could be captured on the timescale of tens of seconds. The results demonstrate new possibilities for investigating intermediate states during mesophase transitions that are important to understand membrane fusion, and they highlight the potential of photoswitchable lipids for designing bespoke drug delivery systems.