Chemically Fueled Active Transport Cascades in Large Unilamellar Vesicles

Biology routinely transduces energy stored in chemical bonds to create transmembrane gradients, which are themselves a crucial on-demand energy store to drive life's vital processes. We report a strategy for the chemically fueled active transport of molecular cargo in large unilamellar vesicles. We outline the features required for driving active transport across phospholipid bilayers. Through a series of experiments in both hybrid lipid-liquid supported membranes and biomimetic vesicles, we demonstrate the transmembrane transport of our diacid cargo and quantify key performance indicators of our system. The active transport mechanism gives rise to an associated generation of transmembrane pH gradients of up to ∼0.3 pH units, comparable to the gradient required to drive ATP synthase. We harness this gradient as an energy source to drive a secondary active transport process through symport/antiport mechanisms. These chemically fueled active transport cascades demonstrate the successive transduction of free energy from chemical bonds to transmembrane proton gradients to transmembrane Na+ or Cl- gradients. Our work establishes the first example of chemically fueled active transport in unilamellar vesicles and demonstrates how transmembrane gradients can both absorb energy and transfer it as part of a greater systems-level, life-like, compartmentalized nanotechnology.