Our synthetic active transport system uses a glass U-tube in which a chloroform phase separates an aqueous sender from an aqueous receiver phase (Fig. ). The sender contains 200 mM MES buffered water at pH 6 and a dicarboxylate as a transporter molecule. At the same time, the receiver is also aqueous buffered at pH 6 by 200 mM MES (Fig. ). By stirring the chloroform phase but not the aqueous phases, we ensure a homogenous mixing of the chloroform phase. In our design, the transporter molecule and fuel partition poorly in the chloroform phase to ensure that passive transport is limited. Passive transport refers to molecules diffusing from one side to the other without fuel, negating the active transport's work. We used the water-soluble EDC as fuel and the anionic dicarboxylate, Cbz-D, as a transporter molecule to meet this requirement (Fig. ). The application of fuel activates the poorly partitioning transporter molecule into its corresponding anhydride, which is expected to partition better. The activated transporter molecule diffuses to the receiver side, where it hydrolyzes and remains trapped.