A MOLECULE that can bite a uranium-containing ion between its "jaws", not unlike the munching blob in the arcade game Pac-Man, could one day lead to a way to clean up groundwater contaminated with the toxic metal.
Uranium leaches into groundwater from natural deposits of its ore, depleted uranium munitions, nuclear facilities and the detritus of uranium mining. It occurs most commonly in the form of the water-soluble uranyl ion, (UO2)2+, in which the uranium atom is linked to two oxygen atoms by double bonds.
Allowing uranyl to react with other substances might change it into a different, insoluble ion, which can be filtered out. But uranium binds very strongly to oxygen - the bonds it forms are 25 per cent stronger than typical double bonds - making the uranyl ion very stable. Combined with its solubility, this makes dissolved uranium virtually impossible to remove. "It's a very problematic, persistent groundwater contaminant," says Polly Arnold, a chemist at the University of Edinburgh in the UK.
Enter Pac-Man. Arnold's colleague Jason Love had been working on improving catalysts for fuel cells using a large organic molecule known as a macrocycle, that can fold in half to form a structure like a pair of jaws. Love was using the gap between the jaws to capture a pair of cobalt ions, but Arnold realised that it was just the right size and shape to clamp onto a uranyl ion.
To read the full article go to
http://environment.newscientist.com/article/mg19726396.200-pacman-molecule-chews-up-uranium-contamination.html or see issue 2639 of New Scientist magazine, 17 January 2008, page 24 in Kevin St Library.
