The humble fruit fly is overturning the science of smell. Using the fruit fly’s sensitive schnoz, scientists now have evidence that the sense of smell isn’t only a matter of molecular shape–it might also have something to do with how the molecules entering the nose vibrate.
Previously, scientists thought that we perceive a particular smell when an olfactory molecule’s shape matches the shape of receptors in our nose. The molecule enters the receptor, and so we perceive the particular smell triggered by that lock-and-key scenario. But in 1996, MIT Biophysicist Luca Turin suggested that the patterns in which molecules vibrate are what control odor.
So Turin teamed up with Efthimios Skoulakis, a researcher at the Alexander Fleming Biomedical Sciences Research Center in Vari, Greece, to test the theory. They did this by harnessing the power of isotopes: deuterium, an isotope of hydrogen, has the same shape as a regular hydrogen atom, but it vibrates at a different frequency because of the added neutrons. If a fruit fly can tell the difference between an atom and its isotope, it suggests that vibrations influence the sense of smell.
Fruit flies, it turns out, can be trained to detect smells, and so the scientists created a maze with two tunnels: in tunnel number one they put chemicals such as octanol, benzaldehyde, or acetophenone, and in tunnel number two they put the deuterated varieties. In each case, the flies were more attracted to the non-isotopic atoms–which means that they could tell the difference between two atoms that had the same shape. As New Scientist reports:
Turin sees the results as a “vindication” of his theory, at least in flies. “My theory was described as impossible physically, implausible biologically, not supported by evidence,” he says. “This is a clear indication that some component of fruit fly olfaction is sensing vibrations.”
Many scientists are excited by this research, and plan on repeating the experiment From New Scientist:
The experiment “really supports this idea that fruit flies have the ability to be quantum detectors”, says Gregg Roman of the University of Houston in Texas, whose lab just started studying isotope detection in fruit flies.
But some scientists are still looking on the study with a healthy skepticism. For example, does adding more neutrons to create the isotopes really only change the vibrations? Could there possibly be some other aspect about the two molecules–some other result of more neutrons–that flies are perceiving? As New Scientist reports:
Leslie Vosshall of Rockefeller University in New York City agrees that the experiment suggests fruit flies can distinguish one isotope from another but says the assumption that this is due to vibrations is an “over-interpretation”.
Even though the research is controversial insofar as it turns an old theory on its head, the experiment was certainly elegant–something you can’t disregard with a mere turning-up of the nose.
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Image: flickr / Greencolander