World's smallest thermometer - a single molecule

02 September 2007
Posted by Chris Smith.

Researchers have found that a green-glowing chemical from a jellyfish can be used as a molecular thermometer.

Known as GFP - green fluorescent protein - the substance is used by biologists to harmlessly label cells. Shining light of a certain wavelength at a cell containing GFP causes the molecule to flash up green. But a closer look at the green light given out reveals that it is not continuous and instead rapidly blinks on and off as the molecule subtley alters its structure.  Now Cecile Fradin and her colleagues from McMaster University in Hamilton, Ontario Canada, have found that the rate of blinking corresponds to the temperature - when things get hotter the blinking slows down, whilst at cooler temperatures the blinking speeds up.

To find out whether this could be used as a miniature optical thermometer the team measured the blink rate at different temperatures between 10 and 50 degrees C.

Writing in the Journal of the American Chemical Society, they found that with this technique they could make measurements to within an accuracy of 1 degree. Previously researchers had tried to use dyes which glow more brightly at different temperatures, but these can be misleading if several molecules congregate together producing a brighter light. The new discovery is likely to prove useful for temperature monitoring applications on miniature lab-on-a-chip diagnostic devices, and even for measuring the temperature of different structures inside living cells.

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