The Purdue researchers sliced the DNA wires with an enzyme called BamH1, one of numerous restriction enzymes that are used in standard genetic engineering techniques to snip DNA so that scientists can alter the genetic structures of organisms like bacteria.
DNA molecules contain "bases" called guanine, adenine, thymine and cytosine, represented as G, A, T and C. The bases combine in numerous sequences, and various restriction enzymes attach to and cut specific sequences, enabling scientists to isolate and snip DNA segments of differing lengths. The enzyme used in the Purdue research cuts segments of DNA containing a sequence of GGATCC.
"We incubate the particles and DNA in a solution, and the electric charge brings them together to form the wire," Ivanisevic said. "Then we basically make smaller wire segments with magnetic particles attached to this DNA sequence."
Because hundreds of different restriction enzymes snip segments containing specific sequences of genetic material, the method might be used in the future to cut DNA wires of varying lengths for building electronic devices.
Ivanisevic and former Purdue physics graduate student Dorjderem Nyamjav were the first to coat DNA with magnetic particles two years ago. Kinsella and Ivanisevic are the first to show that the BamH1 enzyme cuts DNA wires.
"We weren't sure the enzyme would be able to recognize the DNA sequence covered with particles," Kinsella said. "We thought the particles might hinder the process."
The researchers found, however, that the particles did not interfere with the process, possibly because the electrical charges are strong enough to hold the particles firmly in place, but weak enough to enable the enzyme to push them out of the way.
"The entire strand of DNA used in this research has been stretched onto silicon oxide surfaces at lengths up to 35 micro