Is smell a quantum effect?

For better or for worse, most of us have our sense of smell working hard every second, every hour and every day - whether or not we are particularly conscious of it. We constantly use, and perhaps take for granted, this sensory equipment. We still do not know how smell works. This is in spite of revolutionary work by Buck and Axel in 2004 (for which they won the Nobel Prize for Physiology or Medicine) that determined what type of receptors the olfactory receptors are and how they are organized.

In a recent publication for the Philosophical Transactions of the Royal Society A, Jennifer Brookes discusses the current condition for theories of signal transduction in olfaction. One theory based on Luca Turin's hypothesis from 1996, holds promise; that an odorant's quantized vibrational mode (a phonon) may facilitate electron tunnelling which constitutes the recognition event in the nose. The novel mechanism is explored and explained.

Controversy still surrounds the conception that humans may ‘smell' vibrations - that smell is a spectral sense - analogous to seeing and hearing. This article clarifies that the mechanism is indeed physically feasible and proposes ways to quantize scent. The philosophy of the article emphasises testing and developing new ideas, particularly quantum ideas, in the context of molecular recognition in biology, with the aim of answering some interesting scientific questions or at least generating new ones!

This work has been published in Philosophical Transactions of the Royal Society A: Visions of the future for the Royal Society's 350th anniversary year (Phil. Trans. R. Soc. A 2010 368, 3491-3502)

Journal link: http://rsta.royalsocietypublishing.org/content/368/1924/3491.full.pdf+html