French scientists reveal the design of a new molecular gate locked by a silver ion.

The gate was designed by a team at Louis Pasteur University, Strasbourg. As well as providing a controllable component for use in molecular machines, the researchers see a future for it as a switch that can store and release ions.

The gate has a porphyrin hinge and a freely rotating handle. The hinge and handle both include a pyridyl group designed to form a complex with a silver ion. When no silver ions are around, the handle can rotate freely around the hinge. As soon as a silver ion enters the gate, however, it forms a complex with both pyridyl groups, locking the handle in place. 

The inspiration for the system came from several places, including public park gates and ATP synthase, an enzyme which acts as a rotating molecular motor, said Wais Hosseini, who led the research. 

'The design principle is interesting because it is rather general and opens the way to set-up many other systems. In particular, we are currently working on other molecular gates based on different types of coordination sites and other metal centres such as mercury or palladium. We're also working on a system operated by proton concentration,' said Hosseini.

'The final goal of our investigation is to open the path to rotational motors with control of the direction of rotation,' he added. 'We are currently working on how to introduce a potential gradient to achieve that.'

Clare Boothby