Performing light-driven electron transfer under non-compartmentalized conditions, with electron donor and acceptor in the outer bulk ([1] 2+ /NADH, XTT in Figure and Table entry 2), significantly reduced the overall electron transfer efficiency, especially under aerated conditions. This suggests that the transmembrane electron transfer is indeed more efficient than a liposome-bulk system, and that compartmentalization might play a large role in accelerating the desired reactions, thereby minimizing the detrimental effect of oxygen. There are several reasons for such an improvement design is that a transmembrane potential can build up, which ultimately stops the transmembrane electron transfer. To balance the buildup of charges across the membrane, we tested two transmembrane ion transporters, gramicidin A and 18-crown-6 ether (also see Table , entries 3,4).