Decoding Odors

Photo credit: Gray's Anatomy This diagram shows the receptor neurons in the nose that convert odors to electrical signals that the brain can interpret.

Turin first came across the vibrational theory in the mid-1980s, noticing that it had first been conceived of in the 1930s, later revived in the 1960s, but both times discarded. With the advent of modern technology, he was able to revisit the theory and apply new testing methods. Vibrational theory states that molecules in every substance generate a specific vibration frequency that the nose interprets as a distinct smell. More specifically, it speculates that the vibration frequency of odor molecules is converted to smell recognition via a form of electron tunnelling with the help of receptors in the lining of the nose. In many ways, according to vibrational theory, the way we smell is similar to the way we hear. A molecule's vibrations play out like a chord of music - but instead of music, we get the chemical melody of scent.

In his investigations, Turin noticed that a vibration producing a wave number of 2500 always produced a smell of sulphur. He then found a different molecule - with the same vibration frequency - that also possessed the same smell: the molecule borane. After looking for molecules that were identical in shape but with different vibrations, he theorised that because they had their own unique "chord patterns", they should have different smells.

Despite achieving an apparent scientific breakthrough, Turin was immediately confronted with criticism from members of the scientific community, who doggedly refused to support the publication of his research. The backstabbing world of scientific peer review is the central preoccupation of Chandler Burr's new acclaimed biography of Turin, The Emperor of Scent (Random House, 2003). (Interestingly, Burr, an ardent supporter of Turin's work, has recently been named by The New York Times as their first ever perfume critic). Despite much vindication from Burr and other members of the press, Turin's vibrational theory - like the shape theory -- has not been immune to inconsistencies. Experiments done in 2004 by Vosshall and Keller at Rockefeller University found three of Turin's proposed predictions on the vibrational nature of smell to be false.

Whether the shape or vibrational theory, a combination of the two - or something completely different - gains further and credible scientific ground remains to be seen. For the foreseeable future, the debate rages on…

For more information:

The Guardian - An Explorer Following his Nose
http://books.guardian.co.uk/reviews/scienceandnature/0,,1773782,00.html

The New York Times - Odorama
http://www.chandlerburr.com/newsite/content/emperorofscent/emperorreview.htm