Finding a Ć¢ā‚¬Å“Needle in a HaystackĆ¢ā‚¬Ā¯ with DNA
About three weeks ago I wrote an item about carbon nanotubes being used in the power grid, and one week prior to that I wrote about DNA being used to assemble nanotechnology. Now I’m writing of how DNA may be used not to build, but to find those nanotubes 50,000 times smaller than a human hair.
Carbon nanotubes are like chicken wire that has been stacked or wrapped in a specific way. The different ways of wrapping are known as chiralities. The carbon nanotubes scientists are looking at for use in the power grid have a chirality that gives them a shape similar to that of an armchair. When making them, they can be difficult to separate out from the other manufactured nanotubes. Now researchers at the US National Institute of Standards and Technology have evolved DNA that will find the nanotubes for them. Previous work has shown DNA could isolate nanotubes meant for semiconductors, and by simple mutations it has been modified for this new search. What the DNA does is wrap itself around the nanotubes to bond its nucleotide bases together, just as double-stranded DNA does. The armchair chirality is the only one that can fit inside the DNA when it is wrapped up, thereby isolating the desired shape like a key fitting a keyhole.
With the DNA holding the nanotubes, traditional means of separating contents of a solution, such as chromatography, may be used to retrieve them.