Chemically fueled active transport.

Biology uses chemical potential differences from molecules like ATP to drive membrane pumps, transporting molecules across mem-branes even against concentration gradients. Here, we report a synthetic system that transports small molecules from an aqueous phase (the sender) to an aqueous receiver across a centimeter-sized immiscible solvent at the expense of chemical energy. Molecules with high chemical potential (fuels) in the sender phase transiently activate the transporter molecule to enter the immiscible solvent and exit on the receiver phase side, thus allowing transport from sender to receiver against a concentration gradient. Importantly, we show this active transport mechanism transports molecules across a hydrophobic barrier without complex pumping machinery. Using a reaction-diffusion model, we determined the critical parameters that determine the efficiency of the active transport. Selective transport enables the sorting of a mixture of different molecules. In future work, we will use these design criteria to actively transport molecules across membranes, e.g., of vesicles, at the expense of chemical fuel, thereby mimicking biological processes and enabling the feeding of synthetic cells.