Scientists Engineer Tunable DNA for Electronics Applications

Estimated reading time: 7 minutes

DNA may be the blueprint of life, but it’s also a molecule made from just a few simple chemical building blocks. Among its properties is the ability to conduct an electrical charge, fueling an engineering race to develop novel, low-cost nanoelectronic devices.

Now, a team led by ASU Biodesign Institute researcher Nongjian "N.J." Tao and Duke theorist David Beratan has been able to understand and manipulate DNA to more finely tune the flow of electricity through it. The key findings, which can make DNA behave in different ways — cajoling electrons to smoothly flow like electricity through a metal wire, or hopping electrons about like the semiconductors materials that power our computers and cellphones — pave the way for an exciting new avenue of research advancements. Over short distances, electrons flow across DNA and spread fast like waves across a pond. Across longer distances, they behave more like particles and hopping takes effect. “Think of trying to get across a river,” explained Limin Xiang, a postdoctoral researcher in Biodesign Institute researcher Nongjian Tao’s lab. “You can either walk across quickly on a bridge or try to hop from one rock to another.” Download Full Image

The results, published in the online edition of Nature Chemistry, may provide a framework for engineering more stable and efficient DNA nanowires, and for understanding how DNA conductivity might be used to identify gene damage.

Building on a series of recent works, the team has been able to better understand the physical forces behind DNA’s affinity for electrons.

“We’ve been able to show theoretically and experimentally that we can make DNA tunable by changing the sequence of the ‘A, T, C, or G’ chemical bases, by varying its length, by stacking them in different ways and directions, or by bathing it in different watery environments,” said Tao, who directs the Biodesign Center for Biolectronics and Biosensors and is a professor in the Ira A. Fulton Schools of Engineering.

Along with Tao, the research team consisted of ASU colleagues, including lead co-author Limin Xiang and Yueqi Li, and Duke University’s Chaoren Liu, Peng Zheng and David Beratan.

Untapped potential

Every molecule or substance has its own unique attraction for electrons — the negatively charged particles that dance around every atom. Some molecules are selfish and hold onto or gain electrons at all costs, while others are far more generous, donating them more freely to others in need.

But in the chemistry of life, it takes two to tango. For every electron donor there is an acceptor. These different electron dance partners drive so-called redox reactions, providing energy for the majority of the basic chemical processes in our bodies.

For example, when we eat food, a single sugar molecule gets broken down to generate 24 electrons that go on to fuel our bodies. Every DNA molecule contains energy, known as a redox potential, measured in tenths of electron volts. This electrical potential is similarly generated in the outer membrane of every nerve cell, where neurotransmitters trigger electronic communication between the 100 trillion neurons that form our thoughts.

But here’s where the ability of DNA to conduct an electrical charge gets complicated. And it’s all because of the special properties of electrons — where they can behave like waves or particles due to the inherent weirdness of quantum mechanics.

Scientists have long disagreed over exactly how electrons travel along strands of DNA, said David N. Beratan, professor of chemistry at Duke University and leader of the Duke team.

“Think of trying to get across a river,” explained Limin Xiang, a postdoctoral researcher in Tao’s lab. “You can either walk across quickly on a bridge or try to hop from one rock to another. The electrons in DNA behave in similar ways as trying to get across the river, depending on the chemical information contained within the DNA.”

Previous findings by Tao (pictured left) showed that over short distances, the electrons flow across DNA by quantum tunneling that spread fast like waves across a pond. Across longer distances, they behave more like particles and the hopping takes effect.

This result was intriguing, said Duke graduate student and co-lead author Chaoren Liu, because electrons that travel in waves are essentially entering the “fast lane,” moving with more organization and efficiency than those that hop.

“In our studies, we first wanted to confirm that this wave-like behavior actually existed over longer distances,” Liu said. “And second, we wanted to understand the mechanism so that we could make this wave-like behavior stronger or extend it to longer distances.“

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