Scientists at the Université de Montréal have used DNA to build the world's smallest antenna. Just 5 nanometers long, the system works likes a two-way radio, receiving light in one color and then re-emitting light in a different one depending on the structural changes to the protein it is attached to.

This unique monitoring approach is reported in Nature Methods. The team used DNA together with a fluorescent molecule. DNA is easier to employ since it is an excellent building block for nanostructures and nanomachines by its very nature. The crucial innovation is that the receiver part of the antenna also works as the sensor that can measure what the protein is doing.

Using DNA also allows for this method to have a lot of versatility. DNA chemistry is relatively simple and programmable. So antennae can be created to suit different investigation needs depending on the protein in question.

"The DNA-based nanoantennas can be synthesized with different lengths and flexibilities to optimize their function," lead author Scott Harroun said in a statement. "One can easily attach a fluorescent molecule to the DNA, and then attach this fluorescent nanoantenna to a biological nanomachine, such as an enzyme. By carefully tuning the nanoantenna design, we have created five nanometer-long antenna that produces a distinct signal when the protein is performing its biological function."

The fluorescence method of communication has many applications and, the team explained, the monitoring doesn’t require innovative lab equipment. Conventional spectrofluorometers, common in many labs, would do the job once the nanoantenna is in place.

"For example, we were able to detect, in real-time and for the first time, the function of the enzyme alkaline phosphatase with a variety of biological molecules and drugs," said Harroun. "This enzyme has been implicated in many diseases, including various cancers and intestinal inflammation."

It's the possibility of studying the exact behavior of proteins that makes this approach very exciting. Having such a feedback system provides insights not just into medicine but also chemical manufacturing.   

"In addition to helping us understand how natural nanomachines function or malfunction, consequently leading to disease, this new method can also help chemists identify promising new drugs as well as guide nanoengineers to develop improved nanomachines," added co-author Dominic Lauzon.

The team stresses the versatility of the nanoantenna and how it can be used to monitor both small and large changes. This can be useful for trying to understand different movements of a single protein or screening many at once.