Network nanotrain arrives on time

Powered by nanoscale motors and controlled by DNA – the latest tiny self-assembling transport networks have been built by researchers in the UK.

The nanotrain system can construct its own network of tracks spanning tens of micrometres in length, transport cargo across the network, and then dismantle the tracks, say researchers from the University of Oxford and the University of Warwick.

Researchers developed a system resembling a bicycle wheel with a central point and spokes radiating outwards. The system is built from DNA and kinesin – a motor protein – which moves along the microtracks carrying control modules made from short strands of DNA.

“DNA is an excellent building block for constructing synthetic molecular systems, as we can program it to do whatever we need,” said Dr Adam Wollman from Oxford’s Department of Physics. “We design the chemical structures of the DNA strands to control how they interact with each other.”

[caption id="attachment_36216" align="alignright" width="200"] This image was taken a minute after the shuttles were refuelled, travelling towards the centre with their cargo of green dye. Credit Adam Wollman/Oxford University[/caption]

Assembly nanobots require two kinesin proteins – allowing them to move tracks around and assemble the network – shuttles only need one kinesin to travel along the tracks, and can either carry cargo, or deliver signals to other shuttles.

“We first use assemblers to arrange the track into ‘spokes’, triggered by the introduction of ATP. We then send in shuttles with green fluorescent cargo which spread out across the track, covering it evenly,” said Wollman. “When we add more ATP, the shuttles all cluster in the centre of the track where the spokes meet.”

Next, signal shuttles are sent along the track to tell the cargo-carrying shuttles to release their cargo into the environment where it disperses, said Wollard. Shuttles programmed with ‘dismantle signals can also be sent to the central hub, telling the tracks to break apart.

The team say that these spoke-like track systems could also be used to speed up chemical reactions by bringing compounds together at a central point; or using DNA to control motor proteins could lead to the development of more sophisticated self-assembly systems.

The researchers were inspired by melanophore – which is used by fish to control their colour. Tracks in their network come from a central point and motor proteins transport pigment around the network, either concentrating it in the centre or spreading it throughout the network.

Transport and self-organisation across different length scales powered by motor proteins and programmed by DNA http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2013.230.html

http://www.youtube.com/watch?v=Gk_XGrndwVw

This time-lapse video shows the network, with tracks shown in red, handling a cargo of fluorescent green dye over a period of eight minutes. There's a flash of bright green when the dye-carrying nanoshuttles are first added, which soon find their way onto the tracks. The shuttles are given ATP fuel at 209 seconds in, powering their journey to the centre of the network. Once they reach the centre at 319s, clean-up shuttles with the 'release' signal are sent in. These remove the dye from the network, leaving the tracks empty but for a few stragglers.

The time is shown in seconds (top left) and the scale bar is 10 micrometres (bottom left). Credit: Adam Wollman/Oxford University