A pleasant aroma relies on good vibrations
6 Mar 2013 by Evoluted New Media
The way molecules vibrate, rather than their shape is responsible for giving substances their characteristic smell according to research conducted at UCL. The researchers tested whether altering how a molecule vibrates on a nanoscale would change the way it smells in order to determine how scent is written into a molecule’s structure.
Luca Turin, formerly a UCL lecturer and now at Alexander Fleming Biomedical Sciences Research Centre in Athens and author of the study said: “this work shows that altering molecular vibrations of molecules changes their smell. Receptors in our noses are acting like tiny spectrometers to identify molecules by their vibrations.”
The work indicates that receptors in our noses are able to detect a nanoscale quantum mechanism called ‘inelastic electron tunnelling’ to detect molecular vibrations, a theory first proposed at UCL in 1996.
The researchers took the musk molecule, commonly used in perfumery and replaced the hydrogen atoms in the molecule with the heavier hydrogen isotope deuterium. Exchanging these isotopes doubles the molecule’s hydrogen mass which alters the molecular vibrations of the substance, but leaves its molecular shape unchanged.
For a long time scientists believed that a molecule’s distinct smell was due to its shape. This seemed a plausible theory as we have several hundred types of receptors in our nose that detect odorants which are similar to other receptors elsewhere in the body that detect things by shape. However, the fragrance industry cannot predict the smell of molecule before it is made, and must make thousands of molecules before it selects the correct scent, indicating flaws in this theory.
Trials with human volunteers enrolled in the study showed that the deuterium musk molecules smell different to the hydrogen musk molecules which suggests that a molecule’s vibrations, rather than its shape contributes to its odour.
“Smell is the least understood of our senses. We can detect and identify tens of thousands of smelly molecules by smell alone. The greatest mystery can be summed up in one questions what makes a molecule smell of rose, lemon or rotten eggs?” said Turin.
