Mainstream researchers have long attributed our sense of smell to a "lock and key" hypothesis. The idea is that every odor molecule that enters our nose has a specific shape that fits a specific receptor—like a key fits a lock—allowing us to detect, say, the acrid aroma of burnt coffee. But the hypothesis leaves some questions unanswered. For one, it doesn't explain, why we can detect tens of thousands of odors with only a few hundred smell receptors. It also doesn't explain why odor molecules with very similar shapes give us such different smells; the molecules that gives us the smell of vodka and rotten eggs are almost identical, for example.
Enter vibrations. Chemists have long known that atoms in a molecule vibrate at a particular frequency, depending on their overall molecular structure. Even molecules that differ by a single atom can vibrate quite differently. In the new study, neurobiologists Maribel Franco and Efthimios Skoulakis at the Alexander Fleming institute in Athens and biophysicist Luca Turin and colleagues at the Massachusetts Institute of Technology tested whether these vibrations could account for our wide range of smell.
— From Do Vibrating Molecules Give Us Our Sense of Smell? at Science magazine. You can also find articles at New Scientist and Nature. Thanks to Tania and everyone else who passed along one or more of the links!
My 5 cents worth: I have read LT’s book, and all I can say is that it made a lot of sense. I mean, hearing = vibration… seeing (especially colour) = vibration. It seems rather strange that smelling would all of a sudden not be based on vibration. The whole lock-and-key thing seems awfully crude actually. But hey, I ain’t no scientist! I am sure the truth of how we smell lies somewhere in between these theories, but for now my money is on LT (and no, I sure don’t agree with all of his perfume reviews so it’s not like I am sucking up here
I’m not a scientist either…really can’t comment.
As a physicist and once-researcher, I always feel excited when quantum theory is called upon to explain daily life.
Involving Schrödinger in my Shalimar delectation would be great for my hidden geek.
The articles are really interesting, thanks for the links, and I am so glad for Luca Turin’s prestigious publications.
The idea of building artificial noses is also very fascinating.
It’s true there is still a lot to explain, I would love to ask Dr. Turin loads of questions – the relevant portion of vibrational pattern (could that account for the fact that humans cannot smell the difference between many isotopes?), the role of symmetry, …
On a side note, I miss:
*) the NZZ folio monthly column;
**) Luca’s and Tania’s blogs
***) updates to the guide.
Tania, Luca, please resume the perfume writing.
Casting my YES vote for luring Tania and Luca back into writing and blogging about perfume!!!!
I especially miss NZZ Folio, because it was often on weird tangents….great fun to read.
I was so engrossed in Chandler Burr’s book about LT’s vibration theory of smell, and shocked by the reaction of the scientific community to the theory – wow. Kudos to LT for continuing his research and pushing the boundary that loves to squash anything that questions the status quo. Keep it up, Luca!!!! All the best to you in your continued quest.
Thanks for sharing! I’m currently reading The Emperor of Scent.
Excuse me, but–the smell of vodka? I thought vodka didn’t have a smell, except for the rather faint smell of ethanol, which is nothing like hydrogen sulfide, the substance that gives us the smell of rotten eggs.
Mind if I clarify? Not a scientist, but I eavesdrop on one.
Rotten eggs apparently contain a mad zoo of hideous-smelling sulfur compounds, including ethanethiol, a molecule that differs from ethanol by one atom and whose vile smell is its main fame. Wikipedia covers it pretty well.
http://en.wikipedia.org/wiki/Ethanol
http://en.wikipedia.org/wiki/Ethanethiol
I didn’t realize there was ethanethiol in rotten eggs, but then I never analyzed a rotten egg, although I have dealt with plenty of other smelly things. Of course, hydrogen sulfide also differs from water in exactly the same way that ethanethiol differs from ethanoI–an oxygen atom is replaced by a sulfur–and hydrogen sulfide smells very bad, whereas water is known for being odorless. Considering such examples, where the sulfur compounds smell bad, while the analagous compounds with oxygen in the same position, which would have the same basic shape, have little or no smell, an inoffensive smell, or even a pleasant smell, I am not sure why the “lock-and-key” theory would have arisen in the first place. It would seem obvious that there is more involved than just the shape of the molecules.
Cheering LT’s scientific work and also hoping he and TS will need a break from hard science at some point and share more insights and anecdotes on perfume through books, articles, seminars or any other medium for that matter. I LOVE The Guide and hugely enjoyed the seminars in DC last fall with PdN.
Love reading this scientific dialogues….thnx all