World's smallest thermometer constructed

Modified DNA sensor still responds to differences as small as 0.05 degrees

DNA as a thermometer? Sounds strange, but it works amazingly well. © Kotkoa
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DNA as a thermosensor: Researchers have constructed the world's smallest thermometer. It is only five nanometers thick and still can detect temperature differences of 0.05 degrees. The secret behind it: The scientists have modified the genetic molecule DNA so that it unfolds linearly and to a defined extent when heated. Due to its length it therefore reveals the temperature in its environment.

The DNA is not only the molecule that stores and passes on our genetic information, it is also suitable as a building material for micro and nano constructions of all kinds. Because their double helix structure and the modular construction of strung bases make them stable and versatile at the same time. DNA researchers have already constructed the smallest diode in the world, a waving nanorobot or tiny rings as microcomponents.

The warmer, the longer

David Gareau and his colleagues from the University of Montreal have now taken advantage of another property of DNA for their construction: the genetic molecule changes its length depending on the temperature. If the DNA is heated, it folds a little further. It is thought that this behavior could serve as a kind of internal thermosensor in living organisms.

Through targeted modification of the base sequence, the researchers have now generated DNA molecules whose length increases linearly and reliably in the temperature range between 30 and 85 degrees Celsius. Of these, therefore, it is already known in advance how long they are at certain values. Measuring their length with the aid of optical sensors reveals the temperature of the DNA solution.

A five nanometer thin thermometer

"This allows us to design thermometers that are only five nanometers thick but still produce an easily readable signal as a function of temperature, " explains Gareau's colleague Arnaud Desrosiers. The DNA thermometer is thus 20, 000 times thinner than a human hair, but still goes down to 0.05 degrees, as the researchers report. display

They have already tested their nano-thermometers: they filled the test vessels of a polymerase chain reaction (PCR) device with their thermometer DNA dissolved in water and allowed the reaction to proceed. In this method of propagating the DNA, the genetic molecules are subjected to multiple cycles of heating and cooling. As the researchers report, their DNA thermometers reliably showed these temperature fluctuations.

Suitable for nanomachines and cells

The extremely small size of the DNA thermometer could allow completely new applications, as Gareau and his colleagues explain. In nanotechnology, for example, such nano-sensors could in the future indicate whether nanomachines are threatening to overheat. But even within ourselves the DNA thermometers could be used:

"We know that the temperature in the human body is kept at 37 degrees, but so far we have no idea if there are any major differences on the nanoscale at the level of the individual cells ", Explains co-author Alexis Vall eB lisle. If one were to introduce the sensor DNA into cells, this could perhaps be determined. (Nano Letters, 2016; doi: 10.1021 / acs.nanolett.6b00156)

(University of Montreal, 28.04.2016 - NPO)