Membrane Transport, A Molecular Straw

Researchers from the A*STAR Institute of Bioengineering and Nanotechnology have synthesized a much smaller molecule, which behaves like a ‘molecular drinking straw' and which may have applications in water purification and elsewhere

For some years, Huaqiang Zeng of the Institute of Bioengineering and Nanotechnology has led a team aiming to produce tubular molecules that could pipe water across membranes. In 2012, they created molecules that stacked into a helical tube; unfortunately, this tube was not particularly good at holding water in its central tunnel.

Undeterred, Zeng's team set out to modify that molecule. Substituting a carboxyphenyl group for a carboxybenzyl group was just what was needed — once again the molecules stacked into a helix, but this time it comfortably held a ‘string' of water molecules.

"The continuous one-dimensional ‘water chain' trapped by the molecules is indispensable for mediating water transport across a lipid membrane," says Zeng.

But early experiments attempting to use osmotic pressure to drive water through the ‘straw' into a membrane-bound compartment (vesicle) drew a blank. "We repeatedly failed to demonstrate the water-transporting ability of the molecule when using a sodium chloride concentration gradient," he says.

"Despite my skepticism, we proceeded to investigate whether a proton gradient could induce water transport. We were very surprised to find that it could."The system is the first known example of ‘proton gradient induced' water transport. "I am not aware of any other man-made or natural system that does this," says Zeng. "It seems to be without precedent."

Source: Nanowerk

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Taxonomy

• Purification
• Membranes
• Nano Materials