Each ribboning strand of DNA in our bodies is built from stacks of four molecular bases, shown here as blocks of yellow, green, blue and orange, whose sequence encodes detailed operating instructions for the cell. New research shows that tinkering with the order of these bases can also be used to tune the electrical conductivity of nanowires made from DNA. Credit: Maggie Bartlett, NHGRI
DNA nanowire improved by altering sequences. DNA molecules don’t just code our genetic instructions. They can also conduct electricity and self-assemble into well-defined shapes, making them potential candidates for building low-cost nanoelectronic devices. A team of researchers from Duke University and Arizona State University has shown how specific DNA sequences can turn these spiral-shaped molecules into electron “highways,” allowing electricity to more easily flow through the strand. The results may provide a framework for engineering more stable, efficient and tunable DNA nanoscale devices, and for understanding how DNA conductivity might be used to identify gene damage.
Scientists have long disagreed over exactly how electrons travel along strands of DNA. Over longer distances, they believe electrons travel along DNA strands like particles, “hopping” from one molecular base or “unit” to the next. Over shorter distances, the electrons use their wave character, being shared or “smeared out” over multiple bases at once. But recent experiments lead by Prof Nongjian Tao provided hints that this wave-like behavior could be extended to longer distances, ie electrons that travel in waves are essentially entering the “fast lane,” moving with more efficiency than those that hop.
Using computer simulations, Beratan’s team found that manipulating these same sequences could tune the degree of electron sharing between bases, leading to wave-like behavior over longer or shorter distances. In particular, they found that alternating blocks of 5 guanine (G) bases on opposite DNA strands created the best construct for long-range wave-like electronic motions. The team theorizes these blocks causes them to “lock” together so wave-like behavior of the electrons is less likely to be disrupted by random wiggling in the DNA strand.
“We can think of the bases being effectively linked together so they all move as one,” Liu said. “This helps the electron be shared within the blocks.” The Tao group confirmed these theoretical predictions using break junction experiments, tethering short DNA strands built from alternating blocks of 3 – 8 guanine bases between 2 gold electrodes and measuring the amount of electrical charge flowing through the molecules.
The results shed light on a long-standing controversy over the They might also provide insight into the design of tunable DNA nanoelectronics, and into the role of DNA electron transport in biological systems. https://today.duke.edu/2016/06/conductivity
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