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  1. #31
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    Redneck Perfumisto's Avatar
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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.
    * * * *

  2. #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.

  3. #33
    ECaruthers's Avatar
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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.

  4. #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.

  5. #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.

  6. #36
    ECaruthers's Avatar
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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.

  7. #37
    ECaruthers's Avatar
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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.

  8. #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.

  9. #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.

  10. #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.

  11. #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

  12. #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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