Molecular machines are ubiquitous in nature. These machines, which are made up of complicated assemblies of proteins, are responsible for a host of processes in living organisms, such as ion transport, ATP synthesis and cell division. In fact, our muscles are controlled by the co-ordinated movement of thousands of these machines.

Although scientists have made remarkable progress in synthesising artificial nanomachines over the last decade, they have not been very successful in co-ordinating the movement of assemblies of these nanodevices so that they behave more like their natural counterparts. Nicolas Giuseppone of the University of Strasbourg and colleagues at Paris-Diderot University may now have overcome this problem.

Making the connection

The researchers have succeeded in connecting thousands of nanomachines together by modifying them with ligands of molecules known as terpyridines that bind to metal ions to produce very long single-chain supramolecular polymers. Each monomer, made of "double-threaded" rotaxanes, is composed of two gliding filaments and contracts and expands over a distance of about 1 nm when the pH of the surrounding solution is changed. However, since this motion is repeated along thousands of joined-up monomers along the polymer chains, the overall contraction/expansion movements occur over a distance of tens of microns. This motion is very similar to that of the gliding units in natural muscle fibre, known as sacormers, explains Giuseppone.

“Our results are experimental proof in an artificial system of an integrated mechanism that is already found in nature,” he told “Potential applications include the construction of nano- and micro-robots but also biomaterials with contractile properties, such as artificial muscle fibres.”

Spurred on by its findings, the team is now trying to amplify the expansion/contraction motion even further and to co-ordinate other types of movement, such as twisting and rotation. Such motion would be like that practised by bacteria when they use their flagella to move.

The present work is reported in Angewandte Chemie International Edition.