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  1. #1

    Default New study contradicts Luca Turin's theory?

    That's what it sounds like to me, but it's a bit technical. Thoughts? Here it is:

    Shakespeare wrote “a rose by any other name would smell as sweet.” But would it if the molecules that generate its fragrance were to change their shape?

    That’s what Dr. Kevin Ryan, Assistant Professor of Chemistry at The City College of New York (CCNY) and collaborators in the laboratory of Dr. Stuart Firestein, Professor of Biology at Columbia University, set out to investigate. Their findings, reported December 22 in the journal “Chemistry & Biology,” shed new insight into how our sense of smell works and have potential applications in the design of flavors and fragrances.

    When odor-producing molecules, known as odorants, pass through the nose, they trigger intracellular changes in a subset of the approximately 400 different varieties olfactory sensory neurons (OSN) housed in the nose’s internal membrane tissue, Professor Ryan explained. The unique reaction pattern produced, known as the olfactory code, is sent as a signal to the brain, which leads to perception of odors.

    Professor Ryan and his team wanted to learn how these receptor cells respond when odorants change their shape. They studied the odorant octanal, an eight-carbon aldehyde that occurs in many flowers and citrus fruits. Octanal is a structurally flexible molecule that can adapt to many different shapes by rotating its chemical bonds.

    The researchers designed and synthesized eight-carbon aldehydes that resembled octanal, but had their carbon chains locked by adding one additional bond. These molecules were tested on genetically engineered OSNs known to respond to octanal. This work was done in Professor Firestein’s laboratory at Columbia.

    The aldehyde molecules that could stretch to their greatest length triggered strong activity in the OSNs. However, those molecules whose carbon chains were constrained into a U shape blocked the receptor and left the cell unable to sense octanal.

    “Conformationally constrained odorants were more selective in the number of OSNs they activated,” Professor Ryan noted. “The results indicate that these odorant molecules might be able to alter fragrance mixture odors in two ways: by muting the activity of flexible odorants present in a mixture and by activating a smaller subset of OSNs than chemically related flexible odorants. This would produce a different olfactory code signature.”

    Olfactory receptors belong to the G-protein coupled receptor (GPCR) class of proteins, a family of molecules found in cell membranes throughout the body. Professor Ryan pointed out that half of all commercial pharmaceuticals work by interaction with proteins within this family. Thus, the findings could also have applications to GPCR drug design, as well.

    This can be found at: http://www.sciencedaily.com/releases...1222163053.htm

  2. #2
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    Default Re: New study contradicts Luca Turin's theory?

    I am going to spend a night in a Holiday Inn Express and then re-read that article.
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  3. #3

    Default Re: New study contradicts Luca Turin's theory?

    The work discussed does not so much contradict Turin's theory as it does ignore it. It is widely accepted that Turin's theory is not correct. The 2004 Nobel Prize in Physiology or Medicine was awarded to Axel and Buck for their discoveries of "odorant receptors and the organization of the olfactory system". This work invalidates Turin's theory.
    http://nobelprize.org/nobel_prizes/m...004/press.html
    "The sense of smell long remained the most enigmatic of our senses. The basic principles for recognizing and remembering about 10,000 different odours were not understood. This year's Nobel Laureates in Physiology or Medicine have solved this problem and in a series of pioneering studies clarified how our olfactory system works. They discovered a large gene family, comprised of some 1,000 different genes (three per cent of our genes) that give rise to an equivalent number of olfactory receptor types. These receptors are located on the olfactory receptor cells, which occupy a small area in the upper part of the nasal epithelium and detect the inhaled odorant molecules.

    Each olfactory receptor cell possesses only one type of odorant receptor, and each receptor can detect a limited number of odorant substances. ..."

    The scientists in the Science Daily article take the results of the 2004 Nobel prize work as a given.
    "When odor-producing molecules, known as odorants, pass through the nose, they trigger intracellular changes in a subset of the approximately 400 different varieties olfactory sensory neurons (OSN) housed in the nose’s internal membrane tissue, Professor Ryan explained. The unique reaction pattern produced, known as the olfactory code, is sent as a signal to the brain, which leads to perception of odors."
    Last edited by dcampen; 26th December 2008 at 10:35 PM.
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  4. #4

    Default Re: New study contradicts Luca Turin's theory?

    I thought Luca's theory had been refuted years ago. Too bad for him, but at least he tried. I bet he could have earned the Nobel prize* for that if he had been right. Georg von Bekesy did win it for his studies on the human ear, and he was wrong, too. Oh well.

    *EDIT: oh, they did win it. That must have sucked for LT. I guess he can now pull a Stephen Hawkins and become famous for his witty and scientific best seller books.
    Last edited by irish; 26th December 2008 at 10:57 PM.
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  5. #5

    Default Re: New study contradicts Luca Turin's theory?

    It's been a while since I read about this, but I'm confused. Do Axel and Buck discuss anywhere how individual receptor cells identify the molecules they are "responsible for?" If I recall correctly, Turin's point was that the mechanism is based not on molecular shape recognition but vibration measurement. Is that question indirectly resolved by their research, because to this layman it doesn't seem to be addressed in the nobel summary?

    Just dug up on wikipedia:http://en.wikipedia.org/wiki/Vibration_theory
    "A 1996 paper by Turin revived the theory by proposing a mechanism, speculating that the G-protein-coupled receptors discovered by Linda Buck and Richard Axel were actually measuring molecular vibrations using inelastic electron tunneling, rather than responding to molecular keys that work by shape alone.[2]"
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  6. #6

    Default Re: New study contradicts Luca Turin's theory?

    From what I remember of the Burr book, there are undeniable facts that simply cannot be reconciled with the accepted theory, and thus it can't be valid (though this doesn't mean LT is right, but at least he has created actual molecules with his theory). I think dcampen is right and that they just ignored LT. However, I also think there are some BNers who know more about this than I do, so I hope they post responses here.

  7. #7

    Default Re: New study contradicts Luca Turin's theory?

    From what I remember of the Burr book, there are undeniable facts that simply cannot be reconciled with the accepted theory
    Not that I remember.

    The one thing the Burr book was good at was manufacturing artificial controversy in order to sell copies of the book. The scientific exposition was terrible. I thought the most egregious "error" was repeatedly and continually confounding the mythical "shape" theory of odor perception with the currently accepted odorant receptor theory of Axel and Buck in order to set up a straw man.
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  8. #8

    Default Re: New study contradicts Luca Turin's theory?

    It's been a while since I read about this, but I'm confused. Do Axel and Buck discuss anywhere how individual receptor cells identify the molecules they are "responsible for?" If I recall correctly, Turin's point was that the mechanism is based not on molecular shape recognition but vibration measurement. Is that question indirectly resolved by their research, because to this layman it doesn't seem to be addressed in the nobel summary?

    Just dug up on wikipedia:http://en.wikipedia.org/wiki/Vibration_theory
    "A 1996 paper by Turin revived the theory by proposing a mechanism, speculating that the G-protein-coupled receptors discovered by Linda Buck and Richard Axel were actually measuring molecular vibrations using inelastic electron tunneling, rather than responding to molecular keys that work by shape alone.[2]"
    Again, there is no such thing as a "shape" theory of odor perception. This Wikipedia page has a good discussion of the accepted olfaction receptor theory of Axel & Buck:
    http://en.wikipedia.org/wiki/Olfactory_receptor
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  9. #9

    Default Re: New study contradicts Luca Turin's theory?

    Take a look at:

    http://www.ted.com/index.php/talks/l..._of_scent.html

    The "fact" I was referring to can be found from 5:23 to 5:40. If that is accurate, shape theory can't account for it, and must not be accepted until a solid explanation can be given. On the other hand, I haven't heard of anything undeniable that refutes Turin's theory. If anyone would like to speak to this in a way us non-scientists can understand, I think many BNers would appreciate it (including me, of course). But one thing I know is that if there is an undeniable fact that contradicts a theory, that theory can't be accepted until there is a way to explain the fact (and that explanation can't violate the laws of nature or logic).
    Last edited by Bigsly; 27th December 2008 at 04:12 AM.

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    Default Re: New study contradicts Luca Turin's theory?

    well, being a scientist, i can say with pure confidence that NO THEORY is really actually ever 100% refuted, being as there are rarely aspects of molecular biology that are ever evidenced as "Fact"

    these are simply theories. Personally I find this new theory a little comical, with its references to G-protein receptors.......most of the body runs on relation to G-protein receptors, so it's not exactly a revelation that olfactory sensation is linked to it as well. There's nothing really too new in the article, as far i can see......just added details to a larger theory, in all likelihood.

    Neuroscience is so complicated....the whole field changes every 10 years or so....so don't be surprised if you see plenty of these theories pop up frequently throughout your lives

    oh....and you'll never seen one that explains things to you....correctly----because it will get overturned shortly anyways!
    Last edited by everso; 27th December 2008 at 04:27 AM.

  11. #11

    Default Re: New study contradicts Luca Turin's theory?

    That is my sense too, everso, but I don't have the credentials to make such a statement. For me, the "bottom line" is obvious, however, and that is if two molecules have the same shape but smell clearly distinct, the smell theory is gone, regardless of whether LT's theory needs further elucidation or not. One can't say that because one theory has problems the other must be right, which is what some of the smell theory people seem to imply (from what I've read). That's where basic logic comes into play. Worry about your own theory being shot full of holes by simple experiments before worrying about what LT says !

  12. #12
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    Default Re: New study contradicts Luca Turin's theory?

    I'll chime in with more detail later, but I agree with everso - theories and their life and death are never as simple as they appear in the daily media, and are even more complicated than what you get on Nova and the like, although I will admit that those folks do an excellent job of balancing what they leave in and leave out.

    Bigsly, I agree that there are many things (including all of these things that Turin cites) which are problematic for extremely simplistic shape theories. On the other hand, the standard key/lock model has worked nicely for so many things. And as everso points out, saying that G-protein-coupled receptors are involved with anything biochemical is like saying tires are involved with cars. Yeah. No surprise.

    We have some facts that are in search of a (likely) complex group of theories which explains everything, such as the many theories needed to answer "why does the car move?" My current view is that Turin has in his hands some facts and a viewpoint which have to be answered, and that the current state of knowledge is inadequate until they are addressed. Noting that modern car keys operate by both shape and electronic signature, it is entirely conceivable that the black box connecting molecules to nerve signals is multideterminate, involving multiple interactions of various types along the way which affect the final outcome. To that degree, I think it is highly likely that Turin is right in that shape alone is wrong.

    Bear in mind that Einstein actually opposed the idea of black holes and wrote a paper disproving them. In a sense, his theory was right, but his own interpretation of it (at that time) was not. Newton falls apart under certain conditions, Einstein under others. Both "theories" are right - and so is whatever comes next. And both are wrong. Thus what everso says is so true - the whole idea of theories as firm objects that don't change with time? Not the way it really is.
    * * * *

  13. #13

    Default Re: New study contradicts Luca Turin's theory?

    I think that is what often happens, that is, an idea works in practice for 90% of applications, but the other 10% is apparently wrong. The problem comes in when those who believe the 90% somehow covers 100%, and they criticize the guy who may be able to explain the 100%, if given the opportunity (which today means big research dollars).

  14. #14

    Default Re: New study contradicts Luca Turin's theory?

    I agree that there are many things (including all of these things that Turin cites) which are problematic for extremely simplistic shape theories.
    The currently accepted theory, for which Axel and Buck received the Nobel prize, is not a shape theory. "Shape theory" exists only as a straw man.

    http://en.wikipedia.org/wiki/Straw_man
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  15. #15

    Default Re: New study contradicts Luca Turin's theory?

    Please, then, state the shape theory explicitly for us.

  16. #16

    Default Re: New study contradicts Luca Turin's theory?

    Please, then, state the shape theory explicitly for us.
    Again and again, there is no accepted "shape theory", it could be whatever you feel you need to set up a suitable straw man.

    http://en.wikipedia.org/wiki/Straw_man
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  17. #17

    Default Re: New study contradicts Luca Turin's theory?

    I don't know how you learned science, but what I learned is that the scientist needs to put a hypothesis forward, then experiments are done which confirm or refute it. It can never be a "fact" because it's always possible that something wasn't controlled for that has a causative role, but you cannot have undeniable experimental data that is inconsistent with it. If "shape theorists" want to be taken seriously, they need to step up and tell us what their hypothesis is. Perhaps they have done this, but I haven't seen it, which is why I asked for it to be stated explicitly. If they can't do that much, all they'll get from me is a bit of laughter.
    Last edited by Bigsly; 27th December 2008 at 11:15 PM.

  18. #18

    Default Re: New study contradicts Luca Turin's theory?

    The currently accepted theory of odor perception, for which Axel and Buck received a Nobel prize, is _not_ a "shape theory".

    http://en.wikipedia.org/wiki/Straw_man
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  19. #19

    Default Re: New study contradicts Luca Turin's theory?

    One thing these two must do is to provide a logical explanation for two molecules of the same shape not smelling very similar (and it can't violate the known "laws of nature," obviously). If someone can supply a link to this explanation, we can move forward. If they have no explanation, I don't see how any reasonable person can take them seriously, regardless of what award they won (President Bush has given out some awards, for example).
    Last edited by Bigsly; 27th December 2008 at 11:37 PM.

  20. #20

    Smile Re: New study contradicts Luca Turin's theory?

    Quote Originally Posted by Bigsly View Post
    That's what it sounds like to me, but it's a bit technical. Thoughts? Here it is:

    Shakespeare wrote “a rose by any other name would smell as sweet.” But would it if the molecules that generate its fragrance were to change their shape?

    That’s what Dr. Kevin Ryan, Assistant Professor of Chemistry at The City College of New York (CCNY) and collaborators in the laboratory of Dr. Stuart Firestein, Professor of Biology at Columbia University, set out to investigate. Their findings, reported December 22 in the journal “Chemistry & Biology,” shed new insight into how our sense of smell works and have potential applications in the design of flavors and fragrances.

    When odor-producing molecules, known as odorants, pass through the nose, they trigger intracellular changes in a subset of the approximately 400 different varieties olfactory sensory neurons (OSN) housed in the nose’s internal membrane tissue, Professor Ryan explained. The unique reaction pattern produced, known as the olfactory code, is sent as a signal to the brain, which leads to perception of odors.

    Professor Ryan and his team wanted to learn how these receptor cells respond when odorants change their shape. They studied the odorant octanal, an eight-carbon aldehyde that occurs in many flowers and citrus fruits. Octanal is a structurally flexible molecule that can adapt to many different shapes by rotating its chemical bonds.

    The researchers designed and synthesized eight-carbon aldehydes that resembled octanal, but had their carbon chains locked by adding one additional bond. These molecules were tested on genetically engineered OSNs known to respond to octanal. This work was done in Professor Firestein’s laboratory at Columbia.

    The aldehyde molecules that could stretch to their greatest length triggered strong activity in the OSNs. However, those molecules whose carbon chains were constrained into a U shape blocked the receptor and left the cell unable to sense octanal.

    “Conformationally constrained odorants were more selective in the number of OSNs they activated,” Professor Ryan noted. “The results indicate that these odorant molecules might be able to alter fragrance mixture odors in two ways: by muting the activity of flexible odorants present in a mixture and by activating a smaller subset of OSNs than chemically related flexible odorants. This would produce a different olfactory code signature.”

    Olfactory receptors belong to the G-protein coupled receptor (GPCR) class of proteins, a family of molecules found in cell membranes throughout the body. Professor Ryan pointed out that half of all commercial pharmaceuticals work by interaction with proteins within this family. Thus, the findings could also have applications to GPCR drug design, as well.

    This can be found at: http://www.sciencedaily.com/releases...1222163053.htm
    Thanks for the link. In a former life I was a biochemist...this is really interesting stuff!

  21. #21

    Default Re: New study contradicts Luca Turin's theory?

    One thing these two must do is to provide a logical explanation for two molecules of the same shape not smelling very similar
    Because they have different binding strengths to the various odor receptors.

    http://en.wikipedia.org/wiki/Olfactory_receptor
    http://en.wikipedia.org/wiki/Ligand_(biochemistry)
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  22. #22

    Default Re: New study contradicts Luca Turin's theory?

    Okay, so the next logical step would be to get a bunch of molecule pairs that are the same shape but smell clearly different and determine the binding strengths, to determine if this ideas is consistent with reality. Has this been done? If so, can anyone provide citations to the actual scientific literature (that is available free online)?

  23. #23

    Default Re: New study contradicts Luca Turin's theory?

    Okay, so the next logical step would be to get a bunch of molecule pairs that are the same shape but smell clearly different and determine the binding strengths, to determine if this ideas is consistent with reality.
    First you would have to define what you mean by same shape. Do propanol, propanal, propanethiol and propylamine have the same shape? But this is not necessary, it has been demonstrated that chemicals that smell similar activate the same spectrum of receptors and chemicals that smell differently activate a different spectrum of recptors.

    Has this been done? If so, can anyone provide citations to the actual scientific literature (that is available free online)?
    Very little scientific literature is available for free on the internet but you could for example read pages 7-10 of Linda Buck's Nobel Prize acceptance speech.
    http://nobelprize.org/nobel_prizes/m...ck-lecture.pdf

    or Google:
    http://www.google.com/search?hl=en&q...ption&aq=f&oq=
    Last edited by dcampen; 28th December 2008 at 02:03 AM.
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  24. #24

    Default Re: New study contradicts Luca Turin's theory?

    Well, one thing that's clear is that you are unaware about just how much scientific literature is available for free. Have you heard of pubmed.com?

    I should disclose why this area of "science" concerns me. A friend told me about a book, "The Billion Dollar Molecule." I read it, and found such passages as:

    “…not all the equations we use to describe those interactions are accurate. Some of them are fudge factors. Some of them are thought to be correct even though the experimental data they’re based on are wrong, only nobody knows that because nobody’s gone back and double-checked the experiments. Some are pure guesses. There are assumptions, biases. There’s user error. There’s imprecision in the hardware and software.”

    And: “I mean, what are the basic concepts of biology and how sure are we of them? Well, there aren’t any, hardly. It isn’t that the people are stupid, it’s that the data isn’t there.”

    These are statements made by "top scientists." And I've read other books which confirm this problem. I am not interested in reading acceptance speeches. If someone wants to claim that his or her theory is to be regarded almost like a religious doctrine, then that theory better be "air tight." There had better not be any undeniable evidence to the contrary, because if there is, that person loses all credibility with me. I have the feeling that in this olfactory field, many are just fiddling around with "models," making all kinds of assumptions, trying to force square pegs into round holes, and viciously attacking (or perhaps worse, totally ignoring) anyone who has evidence to the contrary. The way to dispel this well-deserved concern is to take on all evidence that appears to support LT's theory and explain, in detail yet comprehensible to those of sound mind, why exactly LT can't be right and why the theory they support is so strong. So far, I haven't seen that done. That is the way I was taught to do scholarship.
    Last edited by Bigsly; 28th December 2008 at 03:13 AM.

  25. #25

    Default Re: New study contradicts Luca Turin's theory?

    Well, one thing that's clear is that you are unaware about just how much scientific literature is available for free. Have you heard of pubmed.com? Come on !
    OK, since you are going to start being nasty then I am finished with this discussion.
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  26. #26

    Default Re: New study contradicts Luca Turin's theory?

    I just can't believe that someone who obviously knows as much as you do about biology doesn't know about pubmed or do you not consider that substantial? I apologize if I offended.

  27. #27
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    Default Re: New study contradicts Luca Turin's theory?

    Quote Originally Posted by dcampen View Post
    Not that I remember.

    The one thing the Burr book was good at was manufacturing artificial controversy in order to sell copies of the book. The scientific exposition was terrible. I thought the most egregious "error" was repeatedly and continually confounding the mythical "shape" theory of odor perception with the currently accepted odorant receptor theory of Axel and Buck in order to set up a straw man.
    Do you think that was merely oversimplification, or the journalistic/editorial propensity to generate marketable controversy (or both)?

    Bigsly - this is what he means by straw man. I'll try to explain a bit. This is also what everso was addressing, and me too - all from different angles. And pay close attention to what TGL said above, because that's my understanding, too.

    The current theory has "moved on" if you will, and the modern receptor theory (thanks for the link, David) has pretty much filled in most of the gaps in the understanding of olfaction - at least from what I can get my hands on. Even if it's possible to label older, cruder receptor-based theory as the boogey-man of "shape theory", rather than saying it's completely mythical, then it's simply not fair to do battle against it. However, Turin is not, really. You can look at this document on his web site to see where he is currently going. As I suspected, he's moving more or less around Axel and Buck and positioning his ideas in the still-black-boxy area of receptor activation, while admitting the unarguable aspects of the current receptor theory.

    Like everso and I are trying to tell you, science is very dynamic.

    The current receptor theory - vis-a-vis the numbers and types of receptors and their wiring at the nose end - is very strong. There was some peripheral research associated with it which was recently invalidated (I think due to scientific misconduct), but it was tangential, and does not in any way affect the big picture, or the question at hand. This isn't like edgy physical and cosmological theory - a ton of speculation and working hypothesis with very little prediction. There is so much good experimentation here, there is no question in my mind whatsoever that the basics of olfaction have been nailed down. In my opinion, Turin's ideas have to operate in the smaller region of currently unknown problem space. I'll get to that later. But let me explain and strengthen what David is saying about the existing theory.

    The existing theory identifies a large number of receptors with (apparently) a high degree of variability in terms of odorant molecules that they discern. Each sensory cell expresses a single type of receptor, and cells of the same type converge their signals together before the signal heads to the brain. This scenario is highly compelling - it is simple, biologically efficient, readily explained by evolution, and (in my opinion) potentially explains everything. The reason for the latter is that it is fundamentally combinatorial. The large number of different receptors provides a very finely-sampled spectrum of responses for every conceivable molecule. It's like vision with a thousand different types of cones at different frequencies. Imagine color vision with 1000 or 2000 colors. The amount of fine-grained differentiation that is possible is likely to be tremendous. Thus, the current state of knowledge alone may be enough to explain everything (just hang on - I'll address those molecules next). However, Turin takes issue with the idea that receptors relying only on shape could account for the facts. He is basically postulating a mechanism by which receptors could involve both shape and electronic interactions. I think everybody agrees with that, but the exact mechanism of the electronic interactions is what he's postulating - and it's something different from what most people have thought.

    Receptor interactions are highly complex. Add to that the fact that we are talking about hundreds or thousands of receptor types. Even if you could have two molecules with truly identical shapes, but different electronics, then one must realize that receptor binding would likely still be differentiable, based on those electronics, when sampled across such a huge number of receptors, or even a small subset. I'm not saying that they have to be differentiable, but it's possible - without resorting to anything elaborate. Because of Occam's Razor - the idea that we shouldn't be fancy if we don't have to be - that's not good for what remains of Luca's core idea - that odorant molecules do the final triggering of the receptor by a quantum mechanical coupling. What if we just make the multitude of receptors sensitive enough based on existing stuff?

    Now if you read that PDF, you'll see that Turin addresses the whole issue of combinatoriality, and actually challenges an experiment that dealt with it by his own analysis of the data. I didn't follow it through myself - I haven't the time nor the will to scrutinize it, so I take his analysis on a bit of faith. But he basically believes that data showing differential odorant profiles at different receptors can be interpreted as being proportional to the hydrophobicity (water-repellancy) of the molecules, leaving his model of the mechanism of ultimate detection still viable. Bottom line - he is making his model fit in with the current model of Axel and Buck.

    I prefer to be open-minded about this. Some of the things that Turin points out are the kind of facts that (I believe) are irritating, and should bother good scientists, who are not content until all the annoying facts are explained. The borane/thiol thing - that bothers me (and I think it should bother good scientists, too.) These molecules are vastly different from an electronic standpoint - far more different than alcohols are from thiols. Yet Turin makes the admittedly cockeyed hypothesis that these things should smell the same based on their quantum energetics in the IR range, and - lo and behold - they do. I'll be honest - I would have a really hard time throwing out that fact. Add in some other stuff in the PDF I cite above, and I'm willing to suspend my opinion for or against his work until there is more evidence. Now I do take issue with some of his work. For instance, he cites triethylamine-borane as being an example of a borane with a shifted vibration, accounting for its loss of the typical borane odor. Well, the fact is also that it's simply a complex between a borane and an amine, and while it's "just" a complex (meaning weakly bound), it's still strong enough of a bond that (in my opinion) there is likely to be a significant difference in receptor interactions merely because of the quenching of the borane's chemistry by the amine. Bottom line - bad example. Still, there are other examples that he has which are slightly more compelling. Taken as a whole, I think there's still room for his theory. And even if he's wrong about the ultimate mechanism, he has assembled an array of questions which need some explanation.

    Now, finally, an explanation of this paper you mention. You can actually look at the structures of the "locked" molecules here. I don't see a lot of contradiction of his theories, because this pinning of the molecules has basically altered their shapes fundamentally. We know that if you make changes to the shapes of aldehydes, they will smell different, although to a trained nose they still all smell like aldehydes. The deeper scientific purpose of the research is hidden in the link you gave, but in the PDF I just cited, it is hinted at. It looks like they were hoping to spot the actual conformation of the octanal ligand in the receptor, based on which one of their locked octanals exhibited increased binding relative to normal octanal. The results, interpreted that way, would argue for a more or less linear conformation, since their cyclopropane analog is the one that did just that. That seems to be echoed in the less detailed article.

    Overall, I see some cases where I think Turin's work would benefit from collaboration with other labs, particularly in double-blinding and quantifying his examples. However, I'm not entirely convinced that non-noses are qualified to carry some of this stuff out. And while I am still skeptical of some of Turin's results, I am also skeptical of some of the labs whose findings have disagreed with his.

    Sorry if this is all a blur, but I got carried away. I hope it's halfway understandable.

    Time for bed. I'll respond as soon as I can tomorrow. Ciao, and g'nite!
    * * * *

  28. #28

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    Default Re: New study contradicts Luca Turin's theory?

    Quote Originally Posted by Redneck Perfumisto View Post
    ...Sorry if this is all a blur, but I got carried away. I hope it's halfway understandable.
    Not a blur, and thank you RP! For the first time I get closer to understanding some of the controversy.
    Last edited by narcus; 28th December 2008 at 09:57 AM.
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    Default Re: New study contradicts Luca Turin's theory?

    Quote Originally Posted by dcampen View Post
    OK, since you are going to start being nasty then I am finished with this discussion.
    he simply asked if you'd heard of Pubmed. a valid question. No need to sit and cry about it.

    Redneck and bigsly, you guys are full of nice insights into this subject...thank you for providing all of this! some very nice reading i must say! cheers. time for me to sit down and read some of the details.....better get me some nice strong coffee!
    Last edited by everso; 28th December 2008 at 01:05 PM.

  30. #30

    Default Re: New study contradicts Luca Turin's theory?

    I am impressed with everyone who is contributing to this thread! I'll just keep lurking and maybe it will all sink in!

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