Preparation and Characterization of Pore-Suspending Biomimetic Membranes Embedded with Aquaporin Z

Aquaporin, a transmembrane protein that functions as a highly selective water channel, has intrigued membrane researchers around the world to attempt synthesizing membranes embedded with aquaporin for water purification. We have molecularly designed pore-suspending biomimetic membranes embedded with Aquaporin Z (AQPz) based on different lipid protein ratios and investigated their local mechanical stabilities by force indentation using atomic force microscopy (AFM). The compatibility between phosphocholine lipid and AQPz was proved by stop-flow experiments, in which the lipid -AQPz (a lipid to protein molar ratio of 2000:1) exhibited 3000-fold higher permeability than the pristine lipid vesicles. A series of vesicles were then ruptured on the pristine porous substrate. The local membrane mechanical stability is further improved by increasing the AQPz content, suggesting that AQPz increases the energy barrier required for a normal force to punch through the resultant biomimetic membrane. If a proper substrate is employed, no much sacrifice in the diffusivity of the lipid -AQPz membrane can be found through the fluorescence recovery after photobleach (FRAP) experiments. With the involvement of the transmembrane water channel protein and a proper substrate, the membrane exhibits great potential in water treatment, especially in the forward osmosis (FO) process.

Acknowledgement

This work was financially supported by the Environment and Water Industry Programme Office (EWI) (NUS grant number: R-279-000-293-272) under the Singapore National Research Foundation (NRF).