A technique for directing individual proteins through nanoscale channels could lead to complicated biological purification and processing devices.
Researchers used naturally occurring molecular motors to create a nanoscopic conveyor belt for the proteins and an electric field to control the flow of traffic.
Scientists from Delft University of Technology in the Netherlands created a network of nanometre-scale channels within a block of glass. They coated the inside of these channels with 鈥渕otor proteins鈥�, called kinesin. These normally transport material inside cells by attaching to them at one end and using their free end to grab and crawl along proteins, called microtubules.
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The inside of the glass channels was coated so that they attracted the end of the kinesin that normally attaches to a cell. This left the other end free to pull free-floating microtubules through the channels. When fed into the channel head first the microtubules all travel in the same direction through it.
Electrodes embedded on either side of a channel, just before a Y-shaped junction, were used to push or pull the negatively charged microtubules so that they were flowed into one of the two branches. Normally a microtubule would attach to the next kinesin ahead of it, but the electric field draws it one side so that it sets off in a chosen direction.
Video game
Switching the electric field allowed the researchers to sort microtubules carrying red or green fluorescent molecules into two different chambers.
(mov format) created by the researchers shows the microscopic traffic junction in action. 鈥淚t鈥檚 a bit like a video game,鈥� says Cees Dekker, the nanotechnologist leading the project. 鈥淪ometimes we miss because more than one molecule comes through at once,鈥� he adds.
Dekker says it should be relatively simple to automate the process, by having a computer monitor the junction for colours and vary the electric field accordingly. He adds that the technique could have a range of applications. 鈥淚t would be possible to use this for purification [of a biological sample], or to integrate many of these in parallel鈥� to create a complex protein analysis device, he suggests.
Motor biophysics
Controlling the microtubules also allows the researchers to learn about the mechanical properties of molecular motors. 鈥淔or now I am interested in using the system to find out more about the biophysics of kinesin,鈥� Dekker says.
This could be crucial for the future of nanotechnology, says Viola Vogel, an expert in biological nanotechnology at the Swiss Federal Institute of Technology, Zurich, who was not involved with the study.
Vogel says using biological motors to transport nanoparticles should be much simpler than having to push them around with an atomic force microscope or laser tweezers, as nanoengineers currently do. 鈥淛ust like building in the macroscopic world, we need good motors to transport materials,鈥� she told 麻豆传媒. 鈥淪ince we have few good artificial motors, biological ones are important.鈥�
Journal reference: Science (vol 312, p 910)
