DNA strands form nano-machineBy Kimberly Patch, Technology Research News
Researchers at Bell Laboratories have adopted the mechanics of DNA's replication process to make a tiny step motor entirely out of DNA. The motor could one day be used to manipulate other molecules.
The key realization that led to the motor design was that one strand of DNA can physically change another, said Bernard Yurke, a distinguished researcher at Lucent's Bell Labs.
Living things use long strands of DNA, which is made up of four types of bases, to store information. When cell DNA replicates, it unzips into two single strands and each single strand attracts complementary bases, which, in turn, form another single strand of DNA paired with the original strand. Similarly, when strands of DNA have complementary sections of bases, the sections attract each other like magnets.
When working with DNA, Yurke noticed that a certain single strand that was manufactured with random sequences folded in on itself like a hairpin when complementary sequences on the single strand paired. What surprised him, however, was that this hairpin DNA was able to unfold and assemble into the structure he intended when complementary strands of DNA were added to the solution. The hairpin strand unfolded because the new strand had more base pairs in common with the hairpin strand as a whole, and that allowed it to also usurp the portions that had doubled up.
"We realized that one strand of DNA could induce changes in the configuration of another strand, and that led us to think about how one could actually build molecular motors out of DNA," said Yurke.
Yurke's DNA motor resembles a pair of tweezers. The tweezer's arms are made of double-stranded DNA and are bound together on one end by a more flexible single strand. The double strands of the arms are not even, leaving single-strand overhangs on the pincer ends of the arms.
The motor works when two single strands of DNA bind with the overhangs to alternately open and shut the tweezers.
The tweezers shut when a "fuel" strand pairs with the overhangs on the tweezer ends. They open when a "removal" strand pairs with a longer portion of the fuel strand then the overhangs are attached to, then takes over the portion paired with the overhangs, pulling the fuel strand off the tweezers.
"When you go from open tweezer to close tweezer and then back to open tweezer you end up with a fuel strand and removal strand hybridized together and that's the waste product." said Yurke.
The DNA motor works in a step process, meaning the researchers must add the fuel strand first, which closes the tweezer, then add the removal strand. Otherwise, the two would simply pair together.
This method can be used to make DNA motors that respond to different fuel and removal strands, Yurke said. "The sequences of the overhangs on the tweezers can be changed so we can close any particular motor simply by adding the strand that closes that particular motor," he said.
This flexibility makes it a clear advance in molecular devices, said Nadrian Seeman, a chemistry professor at New York University. "We produced a device about a year and a half ago that was triggered by a small chemical [but] this one is triggered by a particular sequence. That means that they'll be able to have a bunch of them and control them all individually and that will be of great utility."
"I think of the [DNA] motors as little fingers that we now have to manipulate things on a nanoscale," said Yurke. "And they will probably first be used to move molecules -- nanoscale objects -- in relation to each other for scientific purposes, simply to see how things interact as you move them in relationship to each other on that kind of length scale."
The technology could be used for this type of scientific investigation within five years, said Yurke. In a decade or more, it may enable more practical applications like medical diagnostics, medical therapeutics and synthetic substance manufacturing, he said.
Yurke's colleagues in the research were Andrew J. Turberfield of Oxford University, England and Bell Labs, and Alan P. Mills Jr., Friedrich C. Simmel, and Jennifer L. Newman, all of Bell Labs. The researchers published a technical paper on their findings in the August 10, 2000 issue of Nature.
Timeline: < 5 years; > 10 years
TRN Categories: Nanotechnology:Biological, Chemical, DNA and Molecular Computing
Story Type: News
Related Elements: Diagram 1, Diagram 2, Diagram 3; Technical paper "A DNA-Fueled Molecular Machines Made of DNA" in Nature, August 10, 2000
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