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  1. #1

    Default Is Luca Turin right about the sense of smell?

    Many of you may be aware that in addition to being co-author of [ame="http://www.amazon.com/Perfumes-Z-Guide-Luca-Turin/dp/0143115014/ref=sr_1_1?ie=UTF8&s=books&qid=1259109072&sr=8-1"]Perfumes: The A-Z Guide[/ame] and an all-around perfume pachuco, Luca Turin is also a biologist who has worked on understanding the underlying mechanism of olfaction.

    The standard theory is that odorant molecules bind to receptors in the nose that sense portions of their shapes. The differential activations of various types of odor receptors combine to create a molecule's distinctive odor profile. Turin disagrees. He has an alternative theory that olfaction works more like infrared spectroscopy. In Turin's model, olfactory receptors detect molecules' preferred vibrational modes.

    Turin's theory is described in Chandler Burr's book [ame="http://www.amazon.com/Emperor-Scent-Story-Perfume-Obsession/dp/0375759816/ref=sr_1_1?ie=UTF8&s=books&qid=1259109119&sr=8-1"]The Emperor of Scent[/ame] as well as in Turin's own book [ame="http://www.amazon.com/Secret-Scent-Adventures-Perfume-Science/dp/0061133841/ref=sr_1_1?ie=UTF8&s=books&qid=1259109150&sr=1-1"]The Secret of Scent[/ame]. I've just finished reading Burr's book and it's quite good. Mostly, it illustrates the old guard of olfactory science closing ranks to ensure that Turin's work doesn't get much exposure.

    The events described in the book are now 10-15 years old, though, and I'm curious as to whether any of you olfactory cognoscenti have heard about additional developments in this field over the last decade. Was Turin on to something, or is he a crackpot with a pet theory?

    I also read [ame="http://www.amazon.com/Chemistry-Fragrances-Perfumer-Consumer-Paperbacks/dp/0854048243/ref=sr_1_2?ie=UTF8&s=books&qid=1259109291&sr=1-2"]The Chemistry of Fragrances[/ame] by Charles Sell and a bunch of other Quest folks. It takes a rather neutral stance on the exact mechanism of olfaction, which is interesting since Sell is named in Burr's book as a strong proponent of the traditional model.

  2. #2
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    Default Re: Is Luca Turin right about the sense of smell?

    In my opinion Luca Turin makes one hell of an argument for his theory.
    'Those who grow too big for their pants will be exposed in the end'--anon

  3. #3

    Default Re: Is Luca Turin right about the sense of smell?

    As someone with a science degree (though not in olfaction theory), I like the way he presented his theory, and some of the evidences he put forward are very compelling.

    However what he failed to do is to irrefutably prove the mechanism that allows this molecular biological spectroscopy to actually be performed in the nose. That part I believe is the weak link. He proposed the possible mechanism, but did not prove the existence of that mechanism.

    That is, as a scientist I would demand, "Don't just tell me what you think is there. Show me it is actually there!"
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    A: Add 'Pour Homme' to the bottle
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  4. #4

    Default Re: Is Luca Turin right about the sense of smell?

    At this point in science, it's a 'creationism/evolution' kind of question.

    Turin makes a very compelling argument, and most of his detractors (from what I've read) simply dismiss it for "not sounding right"...not one of them having a 'silver bullet' argument that kill's Turin's theory.

    Burr's book, if accurate, makes a lot of Turin's loudest detractors in the science world look like petulant zealots who take it personally. (read: bad scientists)

    Remember: Turin's theory (like Darwin's) is just that at this point: a theory yet unproven. Funny then that "scientists" are looking to silence it. That's not very scientific.

  5. #5

    Default Re: Is Luca Turin right about the sense of smell?

    Theory is all fine and dandy and may be helpful in pushing out papers but concrete experimental results and systems is what everyone cares about.
    -

  6. #6

    Default Re: Is Luca Turin right about the sense of smell?

    Obviously. Thus far, nobody on either side can carve anything in stone, but it's like Turin's "I have this idea that seems to fill the gaps in current wisdom..." versus the establishment's "we don't know, therefore you must be wrong".

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    Default Re: Is Luca Turin right about the sense of smell?

    Theory is where it all starts.
    'Those who grow too big for their pants will be exposed in the end'--anon

  8. #8

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by kbe View Post
    Theory is where it all starts.
    True, but this theory started a while ago. Its time to display a proof-of-concept as well as concrete molecules based on this theory, which is what Turin has been working on with his Virginia based startup and MIT. Less hand-waving, more tangible results.
    Last edited by zztopp; 25th November 2009 at 02:45 AM.
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  9. #9
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    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by NillaGoon View Post
    Mostly, it illustrates the old guard of olfactory science closing ranks to ensure that Turin's work doesn't get much exposure.
    Personally, I don't see the situation as that conspiratorial. Most people are moderately skeptical, as they should be, IMO, whenever a new theory comes along, or an old and/or "discredited" one is revived. In fact, I would say that - for a minority theory - the vibrational hypothesis has surprisingly good exposure. Both experimentalists and theoreticians love having alternative theories to add a bit of comparative excitement to their work. Even when people are interpreting results against the vibrational hypothesis, I tend to believe they're quite thankful it's there as a target of investigation.

    Science always has a hard time drawing the line on treatment of minority viewpoints. Witness the recent "climategate". I'll bet there are some scientists now who wish they had worked harder on discrediting work than on discrediting people. I think that it pays to treat minority viewpoints - and those who hold them - with respect, and to help find the truth in those viewpoints.

    Quote Originally Posted by NillaGoon View Post
    The events described in the book are now 10-15 years old, though, and I'm curious as to whether any of you olfactory cognoscenti have heard about additional developments in this field over the last decade. Was Turin on to something, or is he a crackpot with a pet theory?
    Turin continues to modify his ideas to fit the facts, just like everybody else. I'm about to read some material he offered to BNers on some recent experimental results involving the effect of zinc nanoparticles on olfactory receptors. I'm curious whether that evidence lends more support to his model, or to the standard model. Exciting stuff. People are welcome to PM him for PDFs of the research. Probably nothing that a lot of us couldn't handle.

    The bottom line is very simple. He sees a correspondence between the vibrational modes of odorants and their olfactory character, as well as a less-than-expected correspondence between simple sterics and olfactory character. He has done due diligence as a scientist, looking for ways that vibrational modes could possibly enter into things. Having found a surprisingly good candidate for a vibration-sensing mechanism (electron tunneling - a thoroughly documented phenomenon), he believes that an electron-transfer mechanism of some kind is most likely involved. The question then shifts to tunneling and electron transfer. Tunneling in enzymes is a hot topic now, so I'm on board with that. Although electron transfer is somewhat hypothetical in the context of current knowledge of receptors, it is not irredeemably so, and may actually be cutting edge. So I'm still potentially on board. And beyond that, there could be other explanations for an apparent linkage between olfactory character and vibrational modes of molecules. There is nothing that prevents both Turin and the standard model from being correct in some way we don't quite get.

    Science has a hard time saying "we don't know yet." That statement is not a big draw for prestige or money. But since I'm in the cheap seats, I can yell whatever I want to at either side. I say the game ain't over to my satisfaction.

    I don't see Turin as a crackpot any more than a lot of respected risky thinkers were/are crackpots. Neither is he a "stick in the mud", resisting change from an old viewpoint. He's more like one of those guys who says "Not so fast - how do you explain THIS?" My response is: good question. How do we explain it? Nothing wrong with asking those pesky questions.

    I don't see it as a pet theory, either, because (a) people usually don't modify those, and (b) he was actually a bit reluctant to take it up in the first place. More like somebody who finds a problem and says "Crap. Somebody has to do something about this."

    On some points, I tend to think he's on to something, and on others, I think the standard model is enough, or that there are alternate explanations that are more like standard thinking about receptors. I may detail those later. My gut feeling is that both sides will have some share of the final explanation of olfactory character. I tend to trust that when scientists see patterns, they are meaningful, although perhaps in ways we don't understand yet.

    Quote Originally Posted by NillaGoon View Post
    I also read The Chemistry of Fragrances by Charles Sell and a bunch of other Quest folks. It takes a rather neutral stance on the exact mechanism of olfaction, which is interesting since Sell is named in Burr's book as a strong proponent of the traditional model.
    Sounds good to me! In many ways I'M a strong proponent of the traditional model. But simply saying that things bind, and that's that, really tells us nothing more than saying that the Schrödinger equation explains everything at the molecular level. I'm open to the possibility that within that truth, there could be correlations between vibrational modes and olfactory character, and that Turin may be on to something in pursuing those.

    PS - GourmandHomme - you hit the nail on the head. That is exactly what he's up to, and where he seems to be headed. If there is something there, then good, and if not, then good as well.
    * * * *

  10. #10

    Default Re: Is Luca Turin right about the sense of smell?

    Science begins with a hypothesis (which contains a claim) or just a notion (to be investigated further, before the development of a specific hypothesis). The end of the process is a theory, not the beginning.

    "At this point in science, it's a 'creationism/evolution' kind of question."

    Creationism posits something unknowable, unmeasurable, etc., so I don't understand how that would fit into science at all (unverifiable notions cannot be examined by the scientific method). As I used to explain it to students, the scientific method is just about doing experiments that are controlled. The ancient Greek "science" (as some might call it, but it really was naturalistic speculation) never focused on this kind of experimentation. In any case, I find much "science" today to be just a pile of assumptions, especially in the biology-related fields.

    What can we (those without funding) do? Well, there's always observation that is irrefutable. For example, I've noticed that if I smell a frag with a certain strong note, then smell another frag with the same note that is also strong, within a short period of time, that note will be eliminated when I smell the second frag. However, at least some of the other notes in the second frag are enhanced, so I can smell them better than I would be able to any other way. Such observations may support one hypothesis or another, and since I've experienced it personally, I would get the answer that I know be accurate ("science" be damned)! LOL.
    Last edited by Bigsly; 25th November 2009 at 03:55 AM.

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    Default Re: Is Luca Turin right about the sense of smell?

    Red is right - scientists love a new theory. I take Turin's seriously. I've read both the books and as many of his papers as I can find on-line.

    The Emperor of Scent is very partisan. I don't know any of the proponents of the shape theory of smell but I wouldn't judge them by that book.

    The shape theory has been the dominant theory of molecular interaction with cells that has guided disease theories and drug developments for decades. Turin does not argue about that. Nothing else in the body uses inelastic electron tunnelling spectroscopy. So I understand if most scientists who are not actively working in the area go with the simpler theory - that evolution modified a standard method to handle smell instead of inventing something completely new. But then I don't know anywhere outside the eye where evolution uses rods and cones. There may be other ways that the body could identify vibrational modes. Last Christmas I talked about this with my old thesis supervisor & he said, "Maybe it's like when you touch a tuning fork to your leg."

    Besides hypotheses and experimental tests, the scientific method also requires that other people be able to reproduce your results. Here Turin's methods are easier to criticize. His correlations between computed vibrational modes and perceived smell depend on how things smell to him. When he smells two molecules that differ left-right or hydrogen-deuterium, he says how they smell different to him. But I haven't read that he's ever tested whether they smell different to others, or to what others. On the other hand, Avery Gilbert is very dismissive of Turin and I haven't seen him say, "X and Y molecules actually do smell the same." So Turin may be right, but I have no way to judge.

    The second half of his correlation between vibrational modes and perceived smell seems now to depend on his on calculations with his own computer program. There are standard measures of vibrational modes, like IR absorption, but he's not using them. Again, his calculations may be right. He may even be offering his code to other researchers. But I can't judge.

    Probably the best argument for Turin's theories is that he's using them, at Flexitral, to design new and valuable smell molecules. The more successes he has, the more likely it is that perceived smell does correlate with what his computer program calculates.

  12. #12

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by ECaruthers View Post
    The Emperor of Scent is very partisan. I don't know any of the proponents of the shape theory of smell but I wouldn't judge them by that book.
    That's the thing, though - TEoS tells only Turin's side of the story because Burr literally couldn't get a single shapist to discuss the vibration theory on the record. For those who haven't read it, there's a five-or-so page "author's note" about two thirds of the way through that directly addresses the question "Why does this book seem so one-sided?"

    I'm inclined to believe Burr when he says that he made a good-faith effort to represent the shapists. But the battle lines seem to have been drawn already and the door was closed. Given the events in the book, there's really no explanation that allows everyone to come out looking reasonable. Either the shapists were venal, myopic, and slipshod in their critiques, or Turin's theory really is kind of nutty. I suppose another scenario that fits the facts would be that the theory was plausible but that Turin angered enough people in his handling of it that the old guard felt entitled to write him off.

    In starting this thread, I was mostly curious to find out if any additional clarity had come to the topic in the intervening decade, especially from a scientific perspective. We can talk all day about which perspective seems most plausible, but it's all just more opinion, three layers away from the source.

  13. #13

    Default Re: Is Luca Turin right about the sense of smell?

    "His correlations between computed vibrational modes and perceived smell depend on how things smell to him..."

    That's where my point comes into play, because if I could smell these molecules I could then draw my own conclusions. You can make all the claims you want, and no matter what your credentials are, you can't change reality. I'll leave it to others to believe the Emperor has a wonderful new outfit.

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    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by NillaGoon View Post
    ...In starting this thread, I was mostly curious to find out if any additional clarity had come to the topic in the intervening decade, especially from a scientific perspective. ...
    Aaaack! I had a huge, detailed, and massively hyperlinked response to this - and it got eaten by my laptop on an automatic reboot. Damn...

    The short version - check out Linda Buck's Nobel Prize lecture, and her stuff over at HHMI. Links below. The answer is that - yes - there is more clarity since Burr's book. The idea of combinatorial receptor codes neatly explains what neither shape nor vibration alone could do. Does vibration still have a potential role? Maybe, but it's iffy, IMO.

    I would say that the landscape has shifted from one where Turin's ideas were minor contenders to explain EVERYTHING, to a situation where they are minor contenders to explain SOMETHING. In my opinion, there is more clarity - in favor of the "combinatorially modified standard model", if you want to call it something. Do receptors still, somehow, test vibration? Perhaps. But it's up to Turin to prove it.

    http://nobelprize.org/nobel_prizes/m...004/index.html

    http://nobelprize.org/nobel_prizes/m...el-lecture.pdf

    http://nobelprize.org/nobel_prizes/m...ck-lecture.pdf

    http://www.hhmi.org/research/nobel/buck.html
    * * * *

  15. #15

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by Redneck Perfumisto View Post
    The short version - check out Linda Buck's Nobel Prize lecture, and her stuff over at HHMI. Links below. The answer is that - yes - there is more clarity since Burr's book. The idea of combinatorial receptor codes neatly explains what neither shape nor vibration alone could do. Does vibration still have a potential role? Maybe, but it's iffy, IMO.
    Thank you for posting this and saving me the effort of looking for all the URLs. I remember seeing all of this when it was first published. As elegantly compelling as Turin's theory is, it probably misses the mark.

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    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by ECaruthers View Post
    Probably the best argument for Turin's theories is that he's using them, at Flexitral, to design new and valuable smell molecules. The more successes he has, the more likely it is that perceived smell does correlate with what his computer program calculates.
    I read The Emperor Of Scent and I was quite impressed with Turin's theory and his reasoning behind it. I also agree with ECaruther's statement above.
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  17. #17

    Default Re: Is Luca Turin right about the sense of smell?

    For me the "silver bullet" that has always made me skeptical of the vibrational theory are these solvents I work with on a daily basis. They are deuterated versions of water, acetone, methanol and dimethyl sulfoxide (DMSO). Deuterium is a hydrogen atom containing one neutron and thus making it one atomic mass heavier. This also changes its vibrational state and should if the vibrational theory hold change the smell of anything where it replaces a hydrogen,
    The dueterated version of water is still odorless.
    The deuterated version of acetone still smells like nail polish remover.
    The deuterated version of Methanol still smells like alcohol
    I would say blinded no person could tell the difference between these pairs of molecules.
    That has always kept me from believing vibration explains everything.
    Does vibration play a part in olfactory recognition?
    In my opinion the answer points to yes. In small cases like the deuterated solvents I think the molecules are too small and simple receptor-olfactory sensation pathways are in effect. as you work your way up with larger and larger molecules it seems likely that vibration plays its part along with the size of the molecule (sterics) and the unique shape of it (chirality).
    I'm still working my mind around what I think about the idea of tunneling and electron transfer. I'm more on board with it than not but this is an area where I need to let the data develop a little more before I'm sold on it.
    as always this is an interesting discussion.
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    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by Somerville Metro Man View Post
    The deuterated version of acetone still smells like nail polish remover.
    The deuterated version of Methanol still smells like alcohol
    I would say blinded no person could tell the difference between these pairs of molecules.
    Thanks, SMM. This is exactly the kind of data I was looking for when I expressed reservations about LT's use of himself as one half of every experiment. And, since LT bases his theory on the axiom that no two different molecules have ever been found that smell the same, this may explain why he is so lightly dismissed by others in the field.

  19. #19

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by Somerville Metro Man View Post
    The dueterated version of water is still odorless.
    Water does not enter the receptor

    Quote Originally Posted by Somerville Metro Man View Post
    The deuterated version of acetone still smells like nail polish remover.
    The smell is due to the ketone, unaffected by deuteration

    Quote Originally Posted by Somerville Metro Man View Post
    The deuterated version of of Methanol still smells like alcohol.
    The smell is due to the hydroxyl, unaffected by deuteration because of rapid exchange

    The paucity of experimental data, correctly pointed out by SMM and Redneck Perfumisto, is about to change for the better

    http://jqi.umd.edu/events/fall-seminars-2009.html

  20. #20

    Default Re: Is Luca Turin right about the sense of smell?

    I love you science people and wish my brain could wrap around it all. This is fascinating thread. I've been trying to understand all of this with my limited background and understanding, Your debate and conversation re most informative.. Carry on!
    "You...put on cologne to write?"(From Midnight in Paris)

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    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by luca turin View Post
    The paucity of experimental data, correctly pointed out by SMM and Redneck Perfumisto, is about to change for the better

    http://jqi.umd.edu/events/fall-seminars-2009.html

    Dr. Turin,
    Are slides or other material from your Nov. 30 seminar available? And did that include new experimental data or were you referring to something else?

    I appreciate that your sense of smell is better developed than most. Can you estimate what part of the population could perceive the differences in smell of the molecules that are central to your criticism of the shape theory?

    Thanks.

  22. #22

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by ECaruthers View Post
    Dr. Turin,
    Are slides or other material from your Nov. 30 seminar available? And did that include new experimental data or were you referring to something else?
    Thanks for your interest ! I am readying this work for publication at the moment, and we are thinking of putting a preprint on Arxiv, though no decision has been made on this.


    Quote Originally Posted by ECaruthers View Post
    I appreciate that your sense of smell is better developed than most. Can you estimate what part of the population could perceive the differences in smell of the molecules that are central to your criticism of the shape theory?

    Thanks.
    Hard to say: my impression is that isotope differences are perceived clearly and reliably by a minority of humans, say 30% (wild guesstimate). However, the new data pertains to animal experiments and is, I think, much better than that.

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    Default Re: Is Luca Turin right about the sense of smell?

    Dr. Turin,
    Please let us know as these results become available. I'm generally too cheap to pay for papers when I've only seen the abstracts. But you've provided extra information about these.

    On an earlier topic, do your computer programs for inelastic electron tunneling spectra give the same results as standard programs usable by other researchers? Or are your programs available to other researchers in your field?

    Thanks.

  24. #24

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by ECaruthers View Post
    Dr. Turin,
    Please let us know as these results become available. I'm generally too cheap to pay for papers when I've only seen the abstracts. But you've provided extra information about these.
    Will post the link as soon as it is available.

    Quote Originally Posted by ECaruthers View Post
    On an earlier topic, do your computer programs for inelastic electron tunneling spectra give the same results as standard programs usable by other researchers? Or are your programs available to other researchers in your field?

    Thanks.
    There are three versions of IETS calculations, two of which are in the public domain:

    1- The very simple minded one I described in J Theor Biol, where the intensity is dx^2.q^2 (squared mode displacements times squared partial charges.

    2- A better mousetrap used by Flexitral which is proprietary

    3- The calculation described by Brookes et al. in Phys. Rev. Letters involving a proper accounting of the deformation caused by an electron point charge before and after tunneling and the "projection" of this deformation on a particular vibrational mode. I don't think many odorants have been calculated yet with this method.

  25. #25

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by luca turin View Post
    Thanks for your interest ! I am readying this work for publication at the moment, and we are thinking of putting a preprint on Arxiv, though no decision has been made on this.

    Hard to say: my impression is that isotope differences are perceived clearly and reliably by a minority of humans, say 30% (wild guesstimate). However, the new data pertains to animal experiments and is, I think, much better than that.
    Can't wait to see this.
    Almost makes me want to take trip on the Acela to see the talk.

    In science the discussion is almost always To Be Continued.....
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  26. #26

    Default Re: Is Luca Turin right about the sense of smell?

    Fantastic thread! I've got Emperor of Scent and The Secret of Scent - both of which I enjoyed a great deal. I'd find it delightful if there really could be a mechanism to support Luca's theory. Reminds me of what I recently read about tectonic plate theory and how it took a while for the mechanism for that to be worked out before the movement of the land masses became widely accepted.

    As a pedantic aside, I found it annoying that in the recent issue of Perfumer & Flavorist the article about how our olfactory system works didn't even mention Luca.

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    Default Re: Is Luca Turin right about the sense of smell?

    Nukapai,
    LMAO! I'm actually old enough to remember when continental drift was one of those weird theories only described on the back page of a comic book, along with the lost continents of Atlantis and Moo.

    Dr. Turin,
    Do all the IETS programs you listed give about the same classifications of scent molecules as in your paper with the 3D odor map?

    Thanks.

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    Default Re: Is Luca Turin right about the sense of smell?

    A great thread and replies from Dr Turin himself !
    http://www.basenotes.net/threads/370...o-Profumo-Onda
    For sale. Carnal Flower and Vero Profumo Onda.

  29. #29

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by ECaruthers View Post
    Nukapai,
    LMAO! I'm actually old enough to remember when continental drift was one of those weird theories only described on the back page of a comic book, along with the lost continents of Atlantis and Moo.

    Dr. Turin,
    Do all the IETS programs you listed give about the same classifications of scent molecules as in your paper with the 3D odor map?

    Thanks.
    I haven't tried the _exact same_ data set with the proprietary method, but I think yes. The Brookes et al. method has not yet been applied to a large odorant set. The problem with an exact method is that it is dependent on the relative orientation of the odorant molecule and the electron path (as it should be), and therefore some sort of spatial averaging is required which is computationally intensive and not easy to implement. This is certainly something my UCL colleagues and I plan to look at in the near future.

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    Default Re: Is Luca Turin right about the sense of smell?

    Thank you, Dr. Turin, for taking the time to reply to our questions today. I think the molecule's orientation to the receptor is probably critical to electron tunneling. (A long time ago I did real solid state physics.) Perhaps shape matching is required for the alignment. Perhaps the two theories are really allies and not enemies.

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    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by luca turin View Post
    The paucity of experimental data, correctly pointed out by SMM and Redneck Perfumisto, is about to change for the better

    http://jqi.umd.edu/events/fall-seminars-2009.html
    Hot damn, Luca! You're queued up with Seth Lloyd and a cutting-edge quantum crypto talk. Maybe the world is ready to start listening to you.

    I have a couple of questions that may go over heads, but you've got the BN geeks all in class, so now's as good a time as any.

    The aldehyde odd/even pattern strikes me as something that screams out for non-steric explanations. Simple steric models can't really explain it easily, IMO.

    First - have you seen this phenomenon in any other homologous series?

    Second - are there any steric attempts to explain this, and if so, what are their problems?

    Also - regarding the zinc stuff. The article comes close to saying it - I say out with it! Do you think it's possible that there is a biological Zn(0) pump of some kind that has been there all along and we simply haven't noticed? It sounds like there hasn't been much thought in the past of checking what part of biological Zn determinations were low-valent. But in any event, the evolutionary advantage of such a thing is pretty clear. The easy transport of the neutral metals is also very intriguing. Nature would be negligent to overlook it, IMO.

    I can see why you're excited by the zinc results now.
    * * * *

  32. #32

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by Redneck Perfumisto View Post
    Hot damn, Luca! You're queued up with Seth Lloyd and a cutting-edge quantum crypto talk. Maybe the world is ready to start listening to you.
    I am buffing up my talk to a high sheen :-)

    Quote Originally Posted by Redneck Perfumisto View Post
    The aldehyde odd/even pattern strikes me as something that screams out for non-steric explanations. Simple steric models can't really explain it easily, IMO.

    First - have you seen this phenomenon in any other homologous series?

    Second - are there any steric attempts to explain this, and if so, what are their problems?
    There is no alternation in any other series I know of, though the sudden appearance of the musk character in macrocyclic ketones at C > 14 is an analogous mystery.

    Steric attempts to explain it: none from experts, but biologists tend to deny the existence of the phenomenon itself :-)


    Quote Originally Posted by Redneck Perfumisto View Post
    Also - regarding the zinc stuff. The article comes close to saying it - I say out with it! Do you think it's possible that there is a biological Zn(0) pump of some kind that has been there all along and we simply haven't noticed? It sounds like there hasn't been much thought in the past of checking what part of biological Zn determinations were low-valent. But in any event, the evolutionary advantage of such a thing is pretty clear. The easy transport of the neutral metals is also very intriguing. Nature would be negligent to overlook it, IMO.

    I can see why you're excited by the zinc results now.
    I agree: the existence of metallic phases in living things is wonderfully interesting: nanoparticles can serve both as batteries and as wires, which could for example lead to clustering of redox enzymes around a metal particle, etc. Some theories about the origin of life postulate a similar function for pyrites.

  33. #33
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    Default Re: Is Luca Turin right about the sense of smell?

    Is this the aldehyde odd-even pattern that biologists tend to deny exists?
    "The ones with an odd number of carbons smell predominately waxy with a citrus character in the background, while those with an even number of atoms smell predominately citrus-like with a waxy character in the background." SoS, p 54

    Has anyone ever tested how widely this is perceived? If there are genes to encode 1000 diffeent receptors, we might not all have all of them.

  34. #34

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by ECaruthers View Post
    Is this the aldehyde odd-even pattern that biologists tend to deny exists?
    "The ones with an odd number of carbons smell predominately waxy with a citrus character in the background, while those with an even number of atoms smell predominately citrus-like with a waxy character in the background." SoS, p 54

    Has anyone ever tested how widely this is perceived? If there are genes to encode 1000 diffeent receptors, we might not all have all of them.
    Yes, that is the pattern I was talking about.

    I don't know how widely it is perceived among "naive" subjects, but every perfumer I have spoken to seems to agree with the general principle. The amusing difficulty, as always with perfumers, is that each aldehyde smells so different to those who use them every day for a living that they tend to perceive differences as more important than similarities.

  35. #35

    Default Re: Is Luca Turin right about the sense of smell?

    From the page LT cited: "One view is that molecular shape governs smell, but this notion has turned out to have very little predictive power..."

    When has that ever stopped a biological claim from getting into a textbook? LOL.

  36. #36
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    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by luca turin View Post
    The amusing difficulty, as always with perfumers, is that each aldehyde smells so different to those who use them every day for a living that they tend to perceive differences as more important than similarities.
    I understand that. In my work also, the developers of new products are supposed to care more about quality than our customers do. And our customers generally care at least as much as their most demanding customer. [I believe this is close to a natural law and helps explain the frustration of enthusiasts when the people making new fragrances seem to care less. But that's another topic.]

    So I think the odd-even aldehydes require at least two receptors (probably two sets of receptors) and each "counts atoms like beads on a rosary." The waxy receptor(s) must signal more strongly in response to odd aldehydes while the citrus receptor(s) must signal more strongly in response to even aldehydes. And each must be able to signal in response to non-aldehyde aromachemicals of the right type.

  37. #37
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    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by Redneck Perfumisto View Post
    Aaaack! I had a huge, detailed, and massively hyperlinked response to this - and it got eaten by my laptop on an automatic reboot. Damn...

    The short version - check out Linda Buck's Nobel Prize lecture, and her stuff over at HHMI. Links below. The answer is that - yes - there is more clarity since Burr's book. The idea of combinatorial receptor codes neatly explains what neither shape nor vibration alone could do. Does vibration still have a potential role? Maybe, but it's iffy, IMO.

    I would say that the landscape has shifted from one where Turin's ideas were minor contenders to explain EVERYTHING, to a situation where they are minor contenders to explain SOMETHING. In my opinion, there is more clarity - in favor of the "combinatorially modified standard model", if you want to call it something. Do receptors still, somehow, test vibration? Perhaps. But it's up to Turin to prove it.

    http://nobelprize.org/nobel_prizes/m...004/index.html

    http://nobelprize.org/nobel_prizes/m...el-lecture.pdf

    http://nobelprize.org/nobel_prizes/m...ck-lecture.pdf

    http://www.hhmi.org/research/nobel/buck.html
    Thanks for the references, Red. Since my last biology course was spring of 1966, it took me a while to read through the two Nobel lectures and the more recent interview. What struck me was the complete silence on the question of how the Odor Receptors "interact with odors translating the energy of odor binding into alteration of membrane potential." The argument between Luca Turin and the shape school seems to me to be whether "the energy of odor binding to the odor receptor" comes from the shape of the odor molecule interacting with the shape of the odor receptor or from inelastic electron tunneling when the two meet (or perhaps from some other vibrational resonance between the two structures). This argument is never mentioned. Instead the Nobel work was for identifying ways that DNA translates into odor receptors, the ways odor receptors connect the nose to the olfactory bulb, and the way that signals from the olfactory bulb are processed in the olfactory cortex. This is indeed wonderful work and it does explain a range of reactions to smell - from programmed biological responses in fruit flies to learning, memory and emotional reactions in BaseNoters.

    Figure 3 of Linda Buck's lecture shows the topology of an odor receptor molecule snaking back and forth through a cell membrane. Since 350-500 of these odor receptors have been identified in humans (and 1000 in the more easily studied mouse) it should be possible for future work to test molecule-receptor interactions in more detail.

    As with many other areas of science we're likely to learn less than we hoped in the next year and more than we imagined in the next decade.

  38. #38

    Default Re: Is Luca Turin right about the sense of smell?

    There have been a number of folks in the scientific/ fragrance communities slashing at Luca's theory as being : simply daft , unscientific, implausable etc. , but no one, to my knowledge has PROVED that his theory is incorrect. If for some reason the theory does not resonate with someone ( pun intended) that's fine... we all have our various vantage points and ways of envisioning complex concepts. What I find thoroughly distasteful however, is how many of the detractors of his theory find it necessary to interject so much emotion, ridicule and in some cases, outright personal attack on Luca for posing his theory.
    What's the issue folks?....
    Then again, there was a time where proposing that the World was round could have rather dire consequences for someone uttering such heresy.
    Also, until such time that there is conclusive, scientific PROOF that his theory is not correct, it is as good as any other concept of the mechanics of olfaction.

    He may be right, he may be wrong, but there is no gain that I can see by the inclusion of emotional content in scientific exploration.

  39. #39

    Default Re: Is Luca Turin right about the sense of smell?

    A bit off topic, but I've been following the situation with the hacked emails of the climate scientists the CRU and their selective manipulation of data/destruction of data and a lot of what I've been reading reminds me of the view of the "consensus" in Emperor of Scent. If their science is so solid then what are they afraid of? I'm not a scientist and it's been a while since I read the book, but I get the impression that there is a lot of "circle the wagons" style politics in science and sometimes the mainstream will want to silence/discredit someone who is outside of their philosophical cabal. It's the whole mentality of "the debate is over, there's nothing more to talk about" that seems to be gaining prevalence. And Dr. Turin, if you see this, I'm curious to see what you make of this situation and if you see parallels.

    Again, I'm not a scientist but I did find Emperor of Scent to be a compelling read, and thought Dr. Turin's theory sounded plausible on every level. I enjoyed reading the above exchanges.

  40. #40

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by Indie_Guy View Post
    A bit off topic, but I've been following the situation with the hacked emails of the climate scientists the CRU and their selective manipulation of data/destruction of data and a lot of what I've been reading reminds me of the view of the "consensus" in Emperor of Scent. If their science is so solid then what are they afraid of? I'm not a scientist and it's been a while since I read the book, but I get the impression that there is a lot of "circle the wagons" style politics in science and sometimes the mainstream will want to silence/discredit someone who is outside of their philosophical cabal. It's the whole mentality of "the debate is over, there's nothing more to talk about" that seems to be gaining prevalence. And Dr. Turin, if you see this, I'm curious to see what you make of this situation and if you see parallels.

    Again, I'm not a scientist but I did find Emperor of Scent to be a compelling read, and thought Dr. Turin's theory sounded plausible on every level. I enjoyed reading the above exchanges.
    I have been following the whole CRU mess with great interest and am delighted that those in favor of open debate and data transparency seem to be winning the argument.

    This said, I do not think there is much of a parallel with the state of play in smell research. I see no evidence of any conspiracy, for example, and I do not think anyone suppressed, manipulated or destroyed data in olfaction.

    The CRU hack reveals what are probably criminal activities, whereas the debate in smell, while occasionally heated and sometimes silly, is within the boundaries of normal science.

  41. #41

    Default Re: Is Luca Turin right about the sense of smell?

    Quote Originally Posted by luca turin View Post
    I have been following the whole CRU mess with great interest and am delighted that those in favor of open debate and data transparency seem to be winning the argument.

    This said, I do not think there is much of a parallel with the state of play in smell research. I see no evidence of any conspiracy, for example, and I do not think anyone suppressed, manipulated or destroyed data in olfaction.

    The CRU hack reveals what are probably criminal activities, whereas the debate in smell, while occasionally heated and sometimes silly, is within the boundaries of normal science.
    Thanks for the sensible reply. I didn't mean to imply that the "shapers" were anywhere near as unscrupulous as the folks at CRU, but I did see a speck of daylight in the notion of what the mainstream considers "settled science". The CRU situation is fascinating.

    All the best,

    Ted

  42. #42

    Default Re: Is Luca Turin right about the sense of smell?

    There are at least two books with the title of "Impure Science." You might want to read both of them !

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