A ghostly property of matter, called quantum tunneling, may aid the quest for accurate, low-cost DNA sequencing and sensor applications, indicates a new research.
Stuart Lindsay and his collaborators at the Biodesign Institute of Arizona State University have done the research.
Tunneling implies that a particle, say an electron, can cross a barrier, when, according to classical physics, it does not have enough energy to do so.
Unraveling the DNA sequences of the human genome a decade ago was a remarkable achievement.
Today, the task of sequencing some 3 billion chemical base pairs of the genome, enough information to fill a 20-volume encyclopedia, remains a daunting challenge, thus far accomplished largely through brute force means.
But, such methods are typically slow and extravagantly expensive.
Stuart Lindsay's technique for observing DNA sequences relies on devices known as scanning tunneling- (STM) and atomic force (ATM) microscopes.
He exploits these sensitive instruments to identify complementary DNA base pairs, evaluating the hydrogen bonds formed between them.
Base pairing rules for DNA dictate that the hydrogen bonds work to join up appropriate nucleotide pairs like jigsaw pieces-adenine with thymine and cytosine with guanine.
The scanning tunneling microscope used in the present study features a delicate electrode tip held very close to the DNA sample.
When this tip is fitted with a particular nucleotide and brought in contact with its complementary mate-embedded in the substrate, the hydrogen bonds stick the bases together and they attach, like tiny magnets.
As Lindsay describes the method, "You have sensing chemicals attached to one electrode and the target you want to sense attached to another one. When the junction spontaneously self-assembles, you get a signal. It's a new way of doing recognition at the atomic scale."
Now, Lindsay's research team has developed a method to identify different DNA base pairs, which could serve as the foundation for a new DNA sequencing technology.
"The tunnel current is there as a readout of how long that molecular pair survived in the junction," Lindsay said. "But, it turns out that it's an incredibly nice way of identifying which molecular pair it was," he added.
Although quantum tunneling seems exotic, Lindsay points out that the routine leaking of electrons from one atom to another to form a chemical bond is a similar process.
If significant challenges to reading single molecules through such a technique can be overcome, the method holds the potential for inexpensive DNA sequencing, operating at the breakneck pace of thousands of base pairs per second.