Graphene-oxide membranes are known to be great filters. They have been modified in the past to be impermeable to all solvents except water. The International Business Times had reported in April that a team of researchers from the University of Manchester has made a breakthrough that could potentially change the way we drink water. They used a grapheme-oxide membrane that can be used as a sieve to remove salt from seawater. Now, the same team has tweaked the filter around a bit to remove the amber pigment from whiskey, making it clear.
Zeolitic imidazolate framework (ZIF) membranes are emerging as a promising energy-efficient separation technology. However, their reliable and scalable manufacturing remains a challenge. We demonstrate the fabrication of ZIF nanocomposite membranes by means of an all-vapor-phase processing method based on atomic layer deposition (ALD) of ZnO in a porous support followed by ligand-vapor treatment. After ALD, the obtained nanocomposite exhibits low flux and is not selective, whereas after ligand-vapor (2-methylimidazole) treatment, it is partially transformed to ZIF and shows stable performance with high mixture separation factor for propylene over propane (an energy-intensive high-volume separation) and high propylene flux. Membrane synthesis through ligand-induced permselectivation of a nonselective and impermeable deposit is shown to be simple and highly reproducible and holds promise for scalability.
Medical science often targets drugs at the proteins in cell membranes. They've developed artificial cell membranes that grow and model themselves just like those in mammal cells, making them ideal for testing how drugs will behave. The trick is to use reversible chemical reactions that remodel phospholipids (key molecules in the cell membrane) and make the cell'recycle' them, rather than generate them from scratch. That, in turn, saves the cell a lot of effort as its membrane grows.
Some antibiotics destroy harmful bacteria by disrupting their membranes. Pitsalidis et al. used a monolayer of lipids as an analog for the membrane in a device designed to measure membrane destruction. The layer is tethered to the surface of an organic electrochemical transducer, where it forms an insulating barrier. The introduction of an antibiotic, such as polymyxin B, disrupts the phospholipids, causing a flux of ions that can be measured as an electrical signal. The authors show that their device can discern molecular-scale differences in the disruption capabilities of two amine-based oligothioetheramide isomers that show a fivefold difference in antibacterial activity.
In bacteria, energy production by the electron transport chain occurs at cell membranes and can be influenced by the lipid composition of the membrane. Budin et al. used genetic engineering to influence the concentration of unsaturated branched-chain fatty acids and thus control membrane viscosity (see the Perspective by Schon). Experimental measurements and mathematical modeling indicated that rates of respiratory metabolism and rates of cell growth were dependent on membrane viscosity and its effects on diffusion. Experiments on yeast mitochondria also showed similar effects. Maintaining efficient respiration may thus place evolutionary constraints on cellular lipid composition.