Florent Samain, a postdoctoral researcher in chemistry and lead author on the Angewandte Chemie paper, used DNA synthesis techniques to generate a library of all 2,401 possible ways that the seven substitute molecules could be combined in a string of four units.
The team then screened all the possible combinations for sensitivity to four different test substances as vapors that differed significantly in their structural and electronic properties.
One substance was commonly used as an aquatic herbicide, another as a solvent in research and industrial applications, another as an inhibitor of mold and bacteria in food and the fourth as an ingredient in products ranging from shoe polish to pesticides, as well as in the preparation of explosives.
The researchers found multiple sensors that showed marked fluorescent responses when exposed to the four test substances. "This is our first try with vapors and it ended up working really well," Kool said.
"What makes these sensors work exceptionally well is that the bases in DNA are stacked on one another, physically touching each other," he said. "DNA bases talk to one another, electronically."
That close physical contact also allows the compounds that Kool's group attaches to the DNA backbone to communicate with each other, which is crucial to their functionality.
What is also crucial, the researchers found out, is the order of the compounds along the DNA backbone. Like the sequence of natural DNA, which varies among different animals, the different sequences of the artificial DNA sensors gave different color changes.
"We saw a couple of examples where we had the same components, but in a different order and got a different response," Kool said. "So clearly they are talking to one another and whoever is next to someone else, it makes a difference."
"One of our long-term goals
|Contact: Louis Bergeron|