Researchers Develop Liquid Form Of DNA

A paper describing the experiments appears in the current issue of the Journal of the American Chemical Society. Authors are graduate students Anthony M. Leone, Stephanie C. Weatherly and Mary Elizabeth Williams and Drs. H. Holden Thorp, professor of chemistry, and Royce W. Murray, Kenan professor of chemistry, all at UNC-CH.

"In the laboratory, DNA is usually in a dilute solution of water to be studied or as a crystalline solid that we really can't do anything with," said Thorp. "Now, we have figured out how to make it in a liquid form so that we and others will be able to process it in various new ways. We've also put it on top of microelectronic circuits and can run electricity through it."

Physically, the new molten salt form of DNA is less like water and more like molasses in January or "honey in wintertime Vermont," Murray said. The material they worked with originated in herring fish.

The team succeed in liquifying the DNA by combining negatively charged DNA crystals with positively charged molten metal complexes containing ethylene oxide tails. Murray, his colleagues and students have employed that molecular trick successfully over the past decade with a variety of other substances.

"There's been a lot of discussion about using DNA to make circuits because it has a built-in ability to recognize complementary sequences of itself," Thorp said. "What has not been clear is how to get DNA on little bits and pieces of material. Since now it's in a thick liquid and is electrochemically active, you can begin to imagine ways to deposit it on tiny surfaces."

A next step will be to determine how the DNA structure affects electrical and macroscopic properties of the liquid, he said. So far, he and the others have only used very long DNA in its double helical form, but plan to determine what will happen if they make the molecules shorter or change their shape.

They also would like to figure out how different DNA sequences can provide different electrical signals. That knowledge could enable them or others to create novel circuits capable of storing and moving electronic information.

Ironically, the idea for conducting the complex experiments grew out of discussions that took place during a doctoral student's oral examination, Murray said. Leone adopted the idea for part of his thesis, and the research proved successful almost immediately.

"For the first time, we were able to observe how the DNA affected current flow during oxidation and how the DNA was oxidized in a process known as mediated electrocatalysis," Murray said. "That process is a well-known phenomenon in fluids, but it's never been observed before in a biological molecule like DNA in a semi-solid environment."

Another characteristic of the liquid DNA that might become even more important than the electrochemistry is that it is soluble in a variety of solvents in which ordinary DNA is not, he said.

"That opens the way for scientific studies of DNA in organic solvents and how it interacts with other molecules," Murray said. "We probably won't pursue this ourselves, but we felt it was potentially important enough that we filed a patent disclosure on it."