28 March 2011

from NatureAsia Website

AFM images showing the movement of

a DNA motor along a DNA track.
 

Molecular motors play a crucial role in many important biological events, such as the separation of chromosomes in cell division and assisting the transcription of DNA into RNA.

Inspired by these sophisticated devices, researchers from Kyoto University in Japan and the University of Oxford in the UK have now developed a method for generating a synthetic molecular transport system using DNA.¹

Taking advantage of the one-of-a-kind ability of nucleic acids to form specific hydrogen bonds, the collaborative team led by Andrew Turberfield and Hiroshi Sugiyama has exploited DNA strands to create track components, motor and fuel for this transport system.

“DNA is a uniquely flexible material that allows the exploration of self-assembling molecular structures and devices,” says Turberfield. “This is because the interactions between components can be programmed very easily using the natural specificity of base-pairing.”

In this all-DNA system, the researchers monitored the motion of a single strand of DNA that acts as a motor on a track.

To manufacture the track, they immobilized 15 single DNA strands known as stators on a raft-like, rectangular DNA origami tile consisting of double helices stitched together through short double-stranded DNA ‘staples’. These stators are complementary to the motor, which hybridizes to one of them, forming a double helix.

To fuel the transport system, the team opted for a ‘nicking restriction’ enzyme that cuts a fragment off the end of the motor-stator double-helix.

Turberfield explains that the dissociation of this fragment causes the motor to migrate to the next stator where it can bind more strongly because of the increased number of base pairs, allowing the cycle to repeat.

“This is described as a ‘burnt bridges’ mechanism because the track is destroyed as the cargo passes,” he says.

Fluorescence imaging and atomic force microscopy (AFM) revealed that the motor travelled in a controlled, linear 16-step movement over a large distance. The AFM imaging (pictured above) captured the motor stepping down the track in real time.

The researchers believe that this controlled motion can be used to direct molecular assembly, producing a nano-scale production line.

“We are now working on programmable systems that function autonomously and can navigate complex systems of tracks,” says Turberfield.

Reference

1. Wickham, S. F. J.1, Endo, M.2,3, Katsuda, Y.4, Hidaka, K.4, Bath, J.1, Sugiyama, H.2,3,4 & Turberfield, A. J.1 Direct observation of stepwise movement of a synthetic molecular transporter. Nature Nanotechnol. 6, 166–169 (2011).

Author affiliation

1. University of Oxford, Department of Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK

2. Institute for Integrated Cell–Material Sciences, Kyoto University, Yoshida-ushinomiyacho, Sakyo-ku, Kyoto 606-8501, Japan

3. Core Research for Evolutional Science and Technology, Japan Science and Technology Corporation, Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan

4. Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan