Nature Chem. doi:10.1038/nchem.544 (2010)

A little help from a template has allowed a long, straight molecule to be tied into a knot.

Molecular knots occur naturally in DNA and proteins, but are difficult to make synthetically. Christopher Hunter at the University of Sheffield, UK, and his colleagues solved the knotty problem by taking a long-chain organic molecule and wrapping it around a zinc ion. On its first circuit around the ion, the molecule formed a loop, and on its second circuit threaded through this loop. The two ends of the molecule then joined up and the zinc ion was removed, leaving an arrangement shaped like a trefoil, the simplest known knot.

The example suggests that it might one day be easy for chemists to make complex molecular machines involving knots.