A DNA-based molecular motor that can navigate a network of tracks

TLDR: It is shown that the path of a motor through a network of tracks containing four possible routes can be programmed using instructions that are added externally or carried by the motor itself, and when external control is used it is found that 87% of the motors follow the correct path.

Abstract: Synthetic molecular motors can be fuelled by the hydrolysis or hybridization of DNA. Such motors can move autonomously and programmably, and long-range transport has been observed on linear tracks. It has also been shown that DNA systems can compute. Here, we report a synthetic DNA-based system that integrates long-range transport and information processing. We show that the path of a motor through a network of tracks containing four possible routes can be programmed using instructions that are added externally or carried by the motor itself. When external control is used we find that 87% of the motors follow the correct path, and when internal control is used 71% of the motors follow the correct path. Programmable motion will allow the development of computing networks, molecular systems that can sort and process cargoes according to instructions that they carry, and assembly lines that can be reconfigured dynamically in response to changing demands.

Frequently asked questions

Q1. What is the effect of blocking strands on the motor?

Stators at track ends contain a single-base mismatch in the enzyme recognition site that prevents cleavage and thus captures the motor when it reaches the end of the track. 

Q2. What is the effect of the instruction carried by amotor on the unlabeled tile?

If the instruction carried by amotor does not act locally then motor(L) on the unlabeled tile would unlock the left-hand branch of the labeled tile and reduce or remove the designed bias toward theright-hand branch of the labeled tile. 

Q3. How many times were the origami samples purified?

Origami samplesof up to 60 μL were purified 3 times, on columns of ~500 μL resin volume, by3centrifugation at 1000 g for 4 minutes. 

Q4. What are the characteristics of a p-net-style robot?

These characteristics provide the elements of control required to implement Petri-Net-style computation28; they also permit complex collective behaviours such as those that underlie ‘social’ robotics29.61. 

Q5. What is the trade off between a programmable and adaptable molecular system?

The capacity to control routing decisions locally, by means of signals carried by the motors that they control, is a particularly significant step: molecular transporters can already operate without the need for external control1-4,7-14; they can now process information autonomously, Individual molecular robotic systems that to respond to local stimuli and pass control signals to each other could lead, for example, to the development of responsive systems for distributed drug manufacture and release. 

Q6. What is the motor's instruction to open the righthand path?

c Motor(R) carries the instruction to open the righthand path, and is directed to S8(R), quenching F8(R). d Motor(L) quenches F8(L). 

Q7. What is the sequence used in the second layer?

The same set of sequences (binding, block and unblock) is used at bothjunctions in the second layer, i.e. after S10(R) and S10(L). 

Q8. How was the annealed strands compared to the motor?

Origami tiles were annealed without the staple corresponding tostator S1, then incubated with a sub-stoichiometric quantity (0.9×) of the S1 + motorduplex for 1 hour at 37 °C to load the motor at the start of the track. 

Q9. What is the trade off between controlling the path taken at a junction and controlling it?

The path taken at a junction can be externally controlled or programmed by information carried by the motor itself (with 87% and 71% of the cargo routed correctly for external and internal control respectively). 

Q10. What was used to determine the location of the motor?

Motor strands modified with biotin were labeled with streptavidin after execution of the program, then imaged by AFM to determine the motor location.