Over on the Facebooks, Matt Strassler points to a BBC story about the role of quantum mechanics in explaining our sense of smell. There aren’t any equations in the article, and I haven’t read the research papers, but the idea seems to be that electrons move from one part of a protein to another part via quantum tunneling. The potential that allows this to happen is only set up if you have the right chemical involved, which is how the protein purportedly “smells” the existence of this chemical. The resulting mechanism is just absurdly sensitive — apparently fruit flies can smell the difference between hydrogen and deuterium (chemically identical, but tiny differences in atomic energy levels from having an extra neutron in the nucleus).
It’s still a controversial theory, but apparently not crackpotty. The question of how important quantum mechanics (as opposed to just its classical limit) is for biological processes was brought up in our earlier post on quantum photosynthesis. Which reminds me in turn of this worthwhile talk by Seth Lloyd, on the basic topic of “quantum life” and photosynthesis in particular. In between learning about how quantum phenomena might remain relevant in the hot, warm environment of a plant, you can enjoy Lloyd’s principled stance not to use PowerPoint under any circumstances.
March 25th, 2011 at 11:31 am
Are we sure this isn’t gonna smell fishy in less than a week?
March 25th, 2011 at 11:35 am
How do they tell their mechanism apart from the hypothesis that what we’re smelling is in reality molecular vibrations? They’d be similar affected by isotopic substitution.
March 25th, 2011 at 11:56 am
Sean, I think you spend too much time on Reddit. Like the rest of us.
http://www.reddit.com/r/science/comments/gb1ir/a_talk_on_how_organisms_have_evolved_to_make_use/
March 25th, 2011 at 2:49 pm
He is cool, but honestly, his fake laugh is so annoying.
March 25th, 2011 at 5:21 pm
IEEE spectrum carried a discussion on Dr Turin’s recent paper at http://spectrum.ieee.org/biomedical/diagnostics/nose-works-like-a-scanning-tunneling-microscope back in February if anyone wants a bit more info.
March 26th, 2011 at 1:04 am
An alternative interpretation is that IR light -rather than electron tunneling- induces the sensation of smell: in both cases transitions between electron’s energy levels would be in question. Callahan has long ago collected evidence supporting this interpretation.
The killer test would be a check whether a beam of IR coherent light at preferred frequency can induce a predictable odor percept. If so, a breakthrough in entertainment industry is to be expected;-).
For TGD based model of olfaction as analog of vision in infra red see http://matpitka.blogspot.com/2011/02/isotope-effect-of-olfaction.html .
March 26th, 2011 at 8:39 am
Interesting stuff. One of a very short list of phenomena in which aspects of “quantum weirdness” affecting electronic configuration plausibly play a biologically relevant role. The only other ones I find very convincing are the aforementioned antenna superposition phenomenon and contributions to nucleobase tautomerization. I’m sure more subtle examples will emerge.
March 26th, 2011 at 9:22 am
It always amuses me when someone who thinks he’s smart (and it’s almost always a “he”) says something like, I don’t use powerpoint because it’s so limiting. Oh but your overhead projector combined with your mouth is so enlightening! The reason you don’t like tools like ppt is because you don’t know how to use them. That’s like saying the piano sucks for relaying musical ideas because it only has 88 keys of defined frequency. He seems to be entertaining these high school kids, though.
March 26th, 2011 at 9:48 am
@ 4. Leblebi,
You’re kidding right? Either that or your not very adept at reading social signals — clearly that was a nervous and awkward laugh — something not unusual around MIT I suspect. Annoying – perhaps. Fake — hardly.
@ 8. Evin,
Wow, such outrage. I agree that making not using powerpoint a matter of principle is a little much, but then, I find being outraged at someone not using powerpoint as a matter of principle also little much.
Anyway, I hardly think he arrived at this conclusion because he couldn’t figure out how to use it.
March 26th, 2011 at 4:15 pm
Chandler Burr’s popular account of Luca Turin’s frustrating attempt to introduce his new quantum theory of smell to a hostile scientific community is a fascinating window both into how the perfume industry works and how some scientific fields erect powerful barriers to maverick ideas. “Emperor of Scent”–a marvelous read.
March 26th, 2011 at 6:22 pm
Very cool. Enjoyed it a lot.
March 27th, 2011 at 6:46 am
[...] Detta blev jag tipsad om på Sean Carrolls utmärkta blog. [...]
March 27th, 2011 at 10:47 pm
I’m very skeptical. Olfactory receptors belong to G-protein coupled receptors. If this happens with olfactory receptors, one would expect that it also happens with other G-protein coupled receptors. But is there any evidence for that? Rhodopsin is also a G-protein coupled receptor. The way rhodopsin works is certainly quantum mechanical in so far as it involves absorption of photon. But that is presumably because absorption of photon changes the shape of retinal.
Of course, everything is quantum mechanical at some level. But I’m not convinced with this particular hypothesis by Luca Turin. And the evidence they have is very indirect. They should use more direct biophysical method to test it.
March 29th, 2011 at 10:58 am
Karl @9, it may not be that Lloyd can’t figure out how to use PowerPoint to communicate what he wants. Edward Tufte, the author of “The Visual Display of Quantitative Information,” also dislike PowerPoint greatly. He wrote and self-published an essay “The Cognitive Style of PowerPoint: Pitching Out Corrupts Within” (http://www.edwardtufte.com/tufte/powerpoint), concerning PowerPoint’s effect to limit our ability to communicate ideas. His cover visually suggests that the presentation software is as limiting as Stalin’s dictims were to thought and discussion in the Soviet Union.
March 31st, 2011 at 12:18 pm
Very interesting & enjoyable talk.
By the way — neither fake nor annoying.
March 31st, 2011 at 10:21 pm
Thanks for posting this. I loved this lecture!
April 18th, 2011 at 3:33 pm
[...] And, via Sean Carroll, I came across an interesting talk by Seth Lloyd on ‘Quantum Life’. He describes ways in which living things take advantage of quantum mechanics – an idea that would have got you laughed out of the room a few years ago. [...]
April 20th, 2011 at 3:52 am
Sean, you’re original posting seems to display a misunderstanding:
“The resulting mechanism is just absurdly sensitive — apparently fruit flies can smell the difference between hydrogen and deuterium (chemically identical, but tiny differences in atomic energy levels from having an extra neutron in the nucleus).”
According to Turin’s theory (as discussed in the referenced article), we would be talking about differences in the VIBRATIONAL, not ATOMIC, energy levels. The vibrational levels should be significantly more sensitive to a doubling in a nuclear mass than the atomic levels, since they depend on the reduced mass of the atom with respect to the rest of the odorant molecule; whereas the atomic levels depend on the reduced mass of the electron with respect to the nucleus.
As a rough estimate, doubling the nuclear mass will shift the Bohr levels by about 1 part in a thousand; but the vibrational levels by about a factor of 2.