Optical control of membrane mechanics via global and red-light-catalyzed, leaflet-selective photolipid switching

Abstract

Azobenzene photolipids are versatile actuators of membrane mechanics and protein function, yet long-wavelength control and leaflet-selective perturbations remain difficult to impose. Here, we address both limitations. First, we show that red-light excitation of a lipidated Nile Blue derivative (NB-lipid) catalyzes rapid and reversible cis[->]trans photoisomerization of co-localized azobenzene photolipids without requiring covalent conjugation. Second, we demonstrate that photocatalysis is predominantly intraleaflet, enabling leaflet-selective actuation by incorporating the membrane-targeted chromophore into only one bilayer leaflet. This enables on-demand and rapid writing of transbilayer mechanical asymmetry, which we track via lock-in capacitance signatures. Critically, symmetric and asymmetric leaflet mechanical perturbations can be evoked within the same membrane by illuminating with blue or red light, respectively. Photocatalysis of electron-rich azobenzenes is anticipated to proceed via the singlet excited state of NB-lipid and thus avoids triplet-state phototoxicity. We underscore the biocompatibility of catalysis by demonstrating the effect of leaflet-specific catalyzed perturbations on the ROS-sensitive mechanosensitive peptide ion channel gramicidin A. Our results establish a novel tool for dissecting the role of dynamic leaflet-specific mechanical changes in membrane remodeling and protein function.