Chemists develop molecular claw to sequester arsenic

Chemists at the University of Oregon have developed a molecular 'claw' that grabs onto arsenic and sequesters it from groundwater, soil, and possibly even from people.

Known as chelators (meaning crab claw) the molecules are made of synthesised sulphur and carbon and are able to trap and immobilise heavy metal atoms. In the presence of a toxic form of arsenic, three of these molecules bond with two arsenic atoms to create a triangular, pyramid-like molecular structure.

It was developed by Darren Johnson, assistant professor of chemistry at the University, along with Jake Vickaryous, a graduate student. "By improving our understanding of these chemical interactions, we hope to develop more effective remediation agents - molecules that can do the work of rendering arsenic harmless," Johnson said.

Although the 'claw' has been shown to work in laboratory settings, Johnson believes the nest step is to verify that the new molecule can render arsenic harmless within the bodies of poisoned individuals. "We're trying to prove that our molecule wants arsenic more than things in your body want arsenic," said Johnson.

Minute amounts of arsenic in drinking water can cause higher incidences of lung, bladder, kidney and skin cancers and is found in numerous groundwater sites around the world. Roughly 10% of US groundwater contains arsenic at levels higher than the World Health Organisation standard of 10 parts per billion.

While they used computer-generated molecular models to predict many of the features they observed, the project also yielded some unexpected, and pleasant surprises.

"We have stumbled upon some surprisingly stable self assembled arsenic complexes. Someday, this approach may provide better agents for sensing and removing arsenic from the environment as well as from the body," Johnson said.

Self-assembly refers to the ability of molecules to naturally join themselves together into larger structures due to the manners in which their geometric and binding structures complement one another. Johnson explained that this was quite promising because it creates a final product that is more stable than the sum of its parts.

This research was first published in Angewandtw Chemie international edition, a chemistry journal. Since then the team has found additional ways of capturing arsenic so that it cannot bond with other substances.



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