Provided are substantially flat membranes that include a block or graft co-polymer and a water transport protein, such as Aquaporin-Z, or a synthetic mimic of such proteins. Also provided are methods of removing contaminants from a liquid, by contacting the liquid with a substantially flat membrane that includes a block or graft co-polymer and a water transport protein or synthetic mimic thereof. Also provided are methods of making such membranes. Further provided are compositions that include at least one active ingredient and vesicles surrounding the active ingredient, where the vesicles include a block or graft copolymer and a water transport protein or synthetic mimic surrounding the active ingredient. Also provided are methods that include administering such compositions to patients.