Molecular machines move to a new level

Ji awen Chen, PhD student of Organic Chemistry at the University of Groningen, has taken molecular machines to a new level. He has engineered a molecular stirrer, created self-assembling nanotubes from motor molecules that can switch to vesicles and back again, and visualized the movement of a single motor molecule. Chen will defend his thesis on 30 January 2015.

In 1999, University of Groningen Professor of Organic Chemistry Ben Feringa (Jiawen Chen’s supervisor) described the first light-driven molecular motor in the journal Nature. Ever since, his group has worked towards applying these motors under everyday conditions.
After more than fifteen years, this now appears feasible. An important first step towards using light-driven motors in biological systems was to make the oily molecules water soluble. This was the first hurdle Chen took: he added water-soluble groups to the motor molecule and made it soapy.

Switch morphology

In an aqueous solution, Chen created a slow-moving light-driven motor molecule that self-assembled into end-capped nanotubes, but would switch morphology into vesicles upon light irradiation, and back into tubes by applying heat. Thus, he was the first to change the shape of a larger nanostructure using motor molecules. This opens up the way for applications to store and deliver compounds in such nanostructures.

Nano-stirrer

Next, Chen fixed a molecular motor to a surface and added a rigid ‘paddle’ to create a light-driven nano-stirrer. Using paddles of different length and rigidity, Chen was able to measure how kinetic and thermodynamic parameters affect the amount of solvent which the stirrer can displace. Future applications could lie in mixing ingredients on a lab-on-a-chip, or moving materials in solution, possibly even inside cells.

Visualization

The visualization of the movement of a single molecular motor was another challenge, solved by attaching a fluorescent group to the motor using a long spacer. Single molecule techniques allowed Chen to directly view the rotary motion, another first in this field. This experiment with a small artificial molecular motor mimics to some extent a classic experiment in which the rotary movement of the much larger cellular ATPase protein complex (which produces the universal energy carrier ATP) was visualized.

Watershed

The work of Jiawen Chen has shown that knowledge about light-driven motors has now reached the point where they can be engineered to perform a specific job, like transport, mixing or moving nanoscale objects. According to his promotor Ben Feringa, Chen’s work represents a watershed in molecular machine engineering. ‘We can build a motor from scratch, visualize its movement, mimic natural motor systems, and place the motors on a surface. This opens up the way for all sorts of smart materials and smart surfaces.’

More information

Jiawen Chen performed his work at the Department of Synthetic Organic Chemistry at the Stratingh Institute for Chemistry, Faculty of Mathematics and Natural Sciences. He will continue working at the same Department as a postdoc researcher. The PhD thesis will be defended on 30 January 2015 at 11 a.m. in Groningen, The Netherlands. The title of his thesis is Advanced molecular devices based on light-driven molecular motors. His promotor is prof.dr. Ben Feringa.