The idea of a robot is not something I’ve especially given thought to before. It did not strike me that while the programming of electrical components was to mimick behaviors like walking and hand movements, these are always viewed in the context of our environment. Walking is but the application of force on a flat surface, and as we know from 3rd law, we’re propelled forth.
To engineer a molecule to walk, we must consider a similar system. Walking here is equivalent to associating and dissociating from a suitable landscape. These landscapes can be designed using DNA origami to generate the scaffold from which appropriate probes can be attached. A nice visual of this is perhaps a mat with dangly bits sticking out. Our walking spider has a body made of streptavidin with its legs as deoxyribozymes. I’ve only come across the idea of deoxyribozymes recently and found it totally brilliant that people saw ribozymes and decided to engineer its counterparts with DNA – more stable and all the jazz. It suggests that DNA can now perform almost all the tasks that have been divided between biomolecules – information storage and maintenance, catalysis, and running the cell and even provide support. I wonder if we can somehow harness this ability to make it breakdown sugars or generate energy so that a cell can sufficiently run on just DNA – like a virus, but self-sufficient.
The deoxyribozymes, through its ability to associate and dissociate preferentially with the substrate over the product on the origami scaffold, enables it to move. The starting line is encoded by immobilizing the spider and allowing it to move on the addition of a complementary trigger that frees it. The concept was demonstrated on a linear track, with some turns by following the system using two colour fluorescent particle tracking. It was also demonstrated using AFM to show the localisation of the molecule from the start of the experiment to positions in the track – it did appear to move from the start, and over 50% did seem to reach the end. The stochasticity in the process makes sense, it is executing something like a biased random walk.
I’m not sure what the real use is yet, but being able to control a molecule’s motion sounds very cool. A thing that struck me is if an origami box is used in drug delivery, such a molecular spider could be immobilized on the box, and on the addition of a trigger, there could be controlled drug release. Just a wild idea.
Sankalpa Venkatraghavan 