For the first time, scientists successfully created a molecular electric motor using the DNA origami method. The motor consists of genetic material that assembles itself and converts electrical energy into kinetic energy.
Paul Rothemund created this technique in 2006, and the research group at TUM later improved it. DNA comprises several lengthy single strands that act as the base for other DNA strands to attach to as counterparts. The DNA sequences are chosen, so the joined strands and folded regions result in the desired structures.
Hendrik Dietz, Professor of Biomolecular Nanotechnology at TUM, said, “We’ve been advancing this fabrication method for many years and can now develop particular and complex objects, such as molecular switches or hollow bodies that can trap viruses. If you put the DNA strands with the right sequences in solution, the objects self-assemble.”
The new nanomotor made of DNA material consists of three components: base, platform, and rotor arm. The base is approximately 40 nanometers high and is fixed to a glass plate in solution via chemical bonds on a glass plate. A rotor arm of up to 500 nanometers in length is mounted on the base so that it can rotate. Another crucial component for the motor to work as intended is a platform between the base and the rotor arm. This platform contains obstacles that influence the movement of the rotor arm. The rotor arm must bend upward a little to pass the obstacles and rotate, similar to a ratchet.
The rotor arms of the motor move randomly in one direction or the other without energy supply. It happens due to random collisions with molecules from the surrounding solvent. When AC voltage is applied through two electrodes, the rotor arms rotate in a targeted and continuous manner in one direction.
Ramin Golestanian, who led the theoretical analysis of the mechanism of the motor, said, “The new motor has unprecedented mechanical capabilities: It can achieve torques in the range of 10 piconewton times nanometer. And it can generate more energy per second than when two ATP molecules are split.”
The motors’ targeted movement results from the electrical forces’ superposition with the forces the rotor arm is subjected to because of the ratchet barriers. An alleged “flashing Brownian ratchet” is realized via the underlying process. The electric field‘s direction, as well as the frequency and amplitude of the AC voltage, allowed scientists to control the rotation’s speed and direction.
Dietz said, “The new motor could also have technical applications in the future. If we develop the motor further, we could use it in the future to drive user-defined chemical reactions, inspired by how ATP synthase makes ATP driven by rotation. Then, for example, surfaces could be densely coated with such motors. Then you would add starting materials, apply a little AC voltage, and the motors produce the desired chemical compound.”
- Anna-Katharina Pumm, Wouter Engelen, Enzo Kopperger, Jonas Isensee, Matthias Vogt, Viktorija Kozina, Massimo Kube, Maximilian N. Honemann, Eva Bertosin, Martin Langecker, Ramin Golestanian, Friedrich C. Simmel & Hendrik Dietz. A DNA origami rotary ratchet motor. Nature (2022). DOI: 10.1038/s41586-022-04910-y