DNA walkers are fascinating molecular machines that have been a focal point of a lot of research on biophysical processes. Recently, researchers at Purdue University developed a new super-resolution microscope that lets them peer even closer into the workings of these machines.
These DNA walkers are synthetic nanomotors designed to convert chemical energy into mechanical movement. They are designed after naturally occurring proteins, such as kinesin or dynein—cargo-transporting proteins that travel along microtubules whose workings are already well-understood. The only difference between naturally occurring nanomotors and synthetic ones being their building blocks—synthetic motors are made out of RNA and DNA. Synthetic walkers are able to transport nanoparticles along carbon nanotubes—performing specific tasks within the cell. Research groups across the globe have been creating these synthetic motors to test potential biomedical and industrial applications. One highly anticipated application area could be the targeted release of anticancer drugs, as demonstrated the researchers at Purdue.
Until recently the mechanisms behind the ‘walking’ was unobservable. Researchers, led by Jong Hyun Choi, developed a novel microscopy system specifically designed to study them. This microscope allows researchers to visualize structures smaller than the wavelength of visible light (250 nm), which is crucial for observing these motors. The process they developed allows one to studying a full walking cycle in a matter of minutes.
They designed their own DNA walking system with an enzymatic core and two arms. Their DNA walker moves along a carbon-nanotube track containing RNA, cutting off sections of RNA as it moves along, and harvesting energy from this process. One arm is tagged with a flourescent protein, allowing the walker to be observed.
They were able to capture images of a DNA walker by exposing it to laser light and capturing the emitted flourecence over thousands of frames. These pictures are then pieced together to form the image of the DNA walker’s movement, showing it is a six-step cycle.
Three key steps were identified in the walking mechanism. Researchers hope to develop ways to target these steps and therefore control the way these walkers move, which could lead to many wonderful ways of using these walkers in tinkering with cells.
(featured image courtesy of Tim Vickers, Wikimedia Commons)