Engineering & Applied Sciences

Xerox fellow takes a ‘macroscopic’ look at DNA supercoiling


James Tobias, rising senior, discusses his Xerox Engineering Research Fellow project with Asst. Prof. Douglas Kelley, at left, during the program’s poster session.

A typical strand of DNA is about 1 meter long, yet it fits within a cell nucleus no larger than a few microns. It does this through a mechanical process called supercoiling.

To further study the mechanics of this phenomenon, Xerox fellow James Tobias did not peer into an electron microscope this summer. Instead, the rising senior took a “macroscopic” look at the general mechanical principles involved, building and testing a device that can apply incremental amounts of torsional strain onto a single strand of polymer.

This allowed him to study the underlying mechanics when a strand of DNA buckles and forms complex structures when it interacts, for example, with enzymes during DNA replication and transcription.

“This is important for not only understanding DNA, but a variety of biological processes,” Tobias explained.

“Because this system is macroscopic, we can see things that other people can’t when they are working with biological structures only a few nanometers across,” added Emeritus Professor Stephen Burns, Tobias’ mentor. “They don’t have control over all the boundary conditions like James has in his experiments.”

The instrumentation needs further refinement, but the device has already yielded interesting information about the mechanics of supercoiling, Burns said.

Tobias said this was his first opportunity to engage in research “to this extent.” Through working mostly on his own, he had a “lot of guidance from Professor Burns, and it doesn’t get much better than that.”

He’s still debating whether to go directly into graduate school, or first work in industry before going for a masters or PhD. In any event, Tobias said, his experience as a Xerox research fellow this summer “made me more open to considering research as a career.”