The permeability and solute transport characteristics of amphiphilic triblock-polymer vesicles containing the bacterial water-channel protein Aquaporin Z (AqpZ) were investigated. The vesicles were made of a block copolymer with symmetric poly-(2-methyloxazoline)-poly-(dimethylsiloxane)-poly-(2-methyloxazoline) (PMOXA 15-PDMS110-PMOXA 15) repeat units. Light-scattering measurements on pure polymer vesicles subject to an outwardly directed salt gradient in a stopped-flow apparatus indicated that the polymer vesicles were highly impermeable. However, a large enhancement in water productivity (permeability per unit driving force) of up to Ϸ800 times that of pure polymer was observed when AqpZ was incorporated. The activation energy (E a) of water transport for the protein-polymer vesicles (3.4 kcal/mol) corresponded to that reported for water-channel-mediated water transport in lipid membranes. The solute reflection coefficients of glucose, glycerol, salt, and urea were also calculated, and indicated that these solutes are completely rejected. The productivity of AqpZ-incorporated polymer membranes was at least an order of magnitude larger than values for existing salt-rejecting polymeric membranes. The approach followed here may lead to more productive and sustainable water treatment membranes, whereas the variable levels of permeability obtained with different concentrations of AqpZ may provide a key property for drug delivery applications.permeability ͉ triblock copolymer ͉ water treatment B iological membranes have excellent water transport characteristics, with certain membranes able to regulate permeability over a wide range. The permeability of membranes such as those present in the proximal tubules of the human kidney (1) can be increased by insertion of specific water-channel membrane proteins known as Aquaporins (AQPs). Other biological membranes, such as those in mammalian optic lenses (2), erythrocytes (3), and many other cell membranes (4) are constitutively AQP-rich. The permeabilities of AQP-rich membranes are orders of magnitude higher than those observed for unmodified phospholipid membranes (5). Additionally, some members of the AQP family have excellent solute retention capabilities for small solutes such as urea, glycerol, and glucose, even at high water transport rates (5, 6). These properties result from the unique structure of the water-selective AQPs. These AQPs have six membrane-spanning domains and a unique hourglass structure (7) with conserved charged residues that form a pore that allows both selective water transport and solute rejection. The AQP used in this study was a bacterial aquaporin from Escherichia coli, Aquaporin Z (AqpZ). AqpZ was selected because it can enhance the permeability of lipid vesicles by an order of magnitude while retaining small uncharged solutes (5). Additionally, AqpZ can be expressed in relatively large quantities in E. coli and has been reported to be quite stable under different reducing conditions and at temperatures of 4°C (5)-properties that make it att...

Surface‐immobilized nanoscale reactors utilizing membrane protein channels are used to generate precisely patterned chemically and biologically active surfaces (see image). The enzymatic conversion of a fluorogenic substrate in the cavity of immobilized nanoreactors is a model reaction demonstrating future potential application of the system in sensors, analytics, microfluidics, and single‐molecule spectroscopy.

Nanoscale devices for energy conversion require the transfer of electrons from one compartment to another. The enzyme complex I, which in vivo mediates electron transfer from NADH to ubiquinone, is an intriguing candidate for this role in nanodevices. However, complex I normally requires the presence of lipids to remain active, potentially limiting its application. Here we demonstrate for the first time that complex I can be actively reconstituted in the synthetic membrane of amphiphilic triblock copolymer vesicles. The functionality of the reconstituted protein was characterized by EPR and activity assays. Its activity is strongly influenced by the molar mass and the block length of the membrane‐forming polymers, and increases with increasing membrane thickness.magnified image

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