Lucas Turin biophycist specialising in perfumery, talks in 2005

This lecture from the TED Talks site is about the opposite spectrum of smells this blog is interested in... nice smells (perfumery). But it's a great explanation of how we perceive smells. Dr Luca Turin is one of the most respected biophysicists in the perfumery business. There are 2 theories as to how we perceive smells: One is the 'lock and key' theory, which is the traditional 'accepted' theory, where a (smelly) molecule 'locks' on to a receptor on our nose and the molecule shape is recognised by the brain. Dr Turin is associated with another theory, the vibrational theory, where the receptors perceive the smell from the particular vibration of the smelly molecule. He starts off the lecture by infusing the whole auditorium with just 400 molecules of a perfume, giving you an idea of the power of many compounds at very low levels. Like many theories, Dr Turin did not 'discover' the vibrational theory. One or 2 researchers had hypothesised it decades ago, but Dr Turin has widely promoted the theory over the last 10-15 years.

http://www.ted.com/index.php/talks/luca_turin_on_the_science_of_scent.html