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  1. #1
    Phero Dude
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    Default Question for the Chemists

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    Chandler Burr has been on the radio talking about Luca Turin and the molecular behaviors relating to smell. Evidently, Turin is expected to win a Nobel prize for his unconventional theory. What I wonder is how his theory and pheromone effectiveness are related and how plausible is the theory. It\'s way over my head to even read...Anybody on here understand that stuff?

  2. #2
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    Default Re: Question for the Chemists

    Smell is the most mysterious of the senses, mysterious in its power to trigger memory and feeling, equally mysterious in the way it operates. Exactly how does the human body receive, process and identify scent?

    \"Smell is unlimited, like the immune system,\" writes Chandler Burr in \"The Emperor of Scent,\" the fascinating story of the man who cracked these mysteries, \"and yet it is instant, like the digestive system.\" We identify smells in an instant, and smell more than 10,000 scents.

    For decades scientists have believed receptors in the nose identify scent molecules by their shape. The atomic structure of a molecule gives each substance a unique shape, and thus a unique smell.

    The seven large international perfume manufacturers known as the Big Boys employ huge laboratories of chemists to manufacture and test new scent combinations. Each company creates between 500 and 2,000 new molecules a year, at a cost of about $4,000 each. Of these, perhaps 20 are interesting and strong enough to pass along to perfumers. Toxicology testing costs another $250,000 per molecule. Eventually, rarely, one will end up on the market.

    All this effort is based on the belief that scent is a product of molecular shape.

    Burr tells the story of Luca Turin, a French-raised biologist with a miraculous nose. Like the hero of Patrick Susskind\'s novel \"Perfume,\" Turin has the ability to identify the most subtle and intricate fragrances, including classic European perfumes, and the equally miraculous power of putting their characteristics into words.

    His 1992 perfume guide became famous within the industry for the precision of his analyses and the startling honesty of his opinions.

    Over the past decade, Turin has come to advance a different theory of scent, based not on shape but on molecular vibration. \"The Emperor of Scent\" tells how he set out to prove his theory, and the even more complex and intriguing story of how he then tried to persuade the scientific community to accept his conclusions.

    Burr\'s book is part scientific report, part detective story, part biography. Turin is an engaging character, bawdy and outspoken and highly opinionated, straight in an realm of expertise inhabited largely by gay men. What gives his story drama is his resistance to inbred, conventional wisdom. Many prestigious careers and many millions in research funds were vested in the idea that scent originated in molecular shape. Turin\'s theory was likely to win him few friends and many powerful opponents.

    \"What the big papers are built on, what gets you publication in Nature and the front page of the New York Times Science Times section, what hooks the grants and hauls in the big prizes,\" writes Burr, \"is the airtight, foolproof experiment. That was what Turin needed.\"

    Burr is a science writer for the Atlantic, where this book incubated. It throws light on the workings of the scientific community, and the surprising opposition a new idea foments when it goes against vested interests.

    \"I have never in my career experienced the degree of juvenile reactions, unprofessionalism, and hysteria as I did from the molecular biologists, chemists, and physicists who believe in Shape,\" writes Burr.

    Redolent with the legends of the world\'s great perfumes, \"The Emperor of Scent\" is that rare book that will appeal both to the aesthete and to the average reader.

    http://www.startribune.com/stories/384/3625935.html

  3. #3
    Phero Dude
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    Default Re: Question for the Chemists

    don\'t know bout \"emperor of scent \"

    but I am about to start reading Patrick Susskind\'s novel \"Perfume\" . It was highly recommended to me. And I\'m sure I will not be disapointed.

  4. #4
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    Default Re: Question for the Chemists

    Nice book review, bivonic. Sums up the content well. I have a review copy that I\'m trying to finish for Human Nature Reviews, and will be writing my review for them in the next few weeks. Meanwhile, I got a copy of the latest paper from Luca Turin, after brief correspondence regarding whether vibration theory might apply to pheromones. Luca\'s still working with consciously processed odors, and probably won\'t get into pheromones anytime soon. The following ref. is a good read; Burr also wrote a book about human sexuality. It\'s available through Amazon.com, I think.

    Burr, C. (1993) Homosexuality and biology. The Atlantic Monthly, 271, 3, 47-65.


  5. #5
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    Default Re: Question for the Chemists

    Some more research I dug up, btw I didn\'t write that review, I should have put the link at the top.

    http://www.leffingwell.com/download/Olfaction4.pdf
    The Vibrational Theory of Odor
    In 1938, Dyson suggested that the infrared resonance (IR) which is a measurement of a molecules vibration might be associated with odor. This idea was popularized by R.H. Wright in the mid 1950’s as infrared spectrophotometers became generally available for such spectral measurements which Wright was able to correlate with certain odorants.

    During the 60’s and early 70’s, vigorous debate raged as to the validity of each theory for classifying chemical odorants.

    By the mid-70’s, it appeared that Wright’s theory had failed a critical test. The optical enantiomers of Menthol and of Carvone smelled distinctly different, although the corresponding infrared spectra were identical. And this theory fell from favor. Recently (August 2001), Leffingwell (http://www.leffingwell.com/chirality.htm) has published on the internet an extensive site that provides over 100 enantiomeric pairs of odorants that have differing odor properties. This site provides both 2-D and 3-D molecular structures along with odor descriptors, odor thresholds and original references.

    Vibrational Induced Electron Tunneling Spectroscope Theory
    Until the seminal dissertation of Luca Turin in 1996, the vibrational theory had been placed under a very dark cloud. Turin, however, has attempted to provide a detailed and plausible mechanism for the biological transduction of molecular vibrations that, while not accepting the mechanical vibrational spectroscopy theory previously proposed, replaces it with a theory that the receptor proteins act as a \"biological spectroscope\". What was proposed is a process called \"inelastic electron tunneling\". Since this paper, which appeared in Chemical Senses in 1996 is available for downloading off the Internet [at http://www.physiol.ucl.ac.uk/research/turin_l/ ], I
    will only outline the process of electron transfer proposed.

    Suffice it to say that the receptor is triggered by an odorant in the presence of NADPH (ß-Nicotinamide Adenine Dinucleotide Phosphate, Reduced Form), which is formed by the enzymatic reduction of ß-Nicotinamide Adenine Dinucleotide Phosphate (NADP). NADPH is widely distributed in living matter and acts as an enzyme cofactor. ß-NADPH is a product of the pentose phosphate pathway, a multifunctional pathway whose primary purpose is to generate reducing power in the form of ß-NADPH. ß-NADPH transfers H+ and 2e- to oxidized precursors in the reduction reactions of biosynthesis. Thus, ß-NADPH cycles between catabolic and biosynthetic reactions and serves as the carrier of reducing power in the same way that ATP serves as the carrier of energy.


    Since according to Turin’s theory the receptor functions as an \"NADPH diaphorase\", it may be significant that high levels of diaphorase activity have been detected in olfactory receptor neurons.

    In order for such electron transfer to occur, Turin proposes from molecular modeling that a zinc binding site is present both on the odorant receptor protein and the G-protein. Zinc’s involvement in olfaction, its ability to form bridges between proteins, its presence in electron transfer enzymes, such as alcohol dehydrogenase and the presence of a the redox-active amino acid cysteine in the receptor’s zinc-binding motif all point to a possible link between electron flow and G-protein transduction. \"Suppose the zinc-binding motif on the olfactory receptor is involved in docking to the olfactory G-protein g(olf), and that the docking involves formation of a disulfide bridge between receptor and G-protein. One would expect to find on g(olf) the other half of a zinc coordination site, for example two histidines in close proximity, and a cysteine nearby.\" A search in the primary sequence of g(olf) finds the motif (His-Tyr-Cys-Tyr-Pro-His). This motif has the requisite properties for docking. It is exposed on the surface of the G-protein and is known to interact with G-protein coupled receptors. In the closely-related adrenergic receptors, a role for cyclic reduction and oxidation of disulfide bridges has been suggested (Kuhl, 1985). It involves cross-linking of the G-protein to the receptor by an S-S bridge which is then
    reduced upon binding of the (redox-active) catecholamine to the receptor, thereby releasing the G-protein. Turin proposes that a similar mechanism may be at work in olfaction.

    Electron tunneling basically is the transfer of electrons down the backbone of the protein and here this would only occur as follows:
    \"When the (olfactory) receptor binding site is empty, electrons are unable to tunnel across the binding site because no empty levels are available at the appropriate energy. The disulfide bridge between the receptor and its associated G-protein remains in the oxidized state. When an odorant (here represented as an elastic dipole) occupies the binding site, electrons can lose energy during tunneling by exciting its vibrational mode. This only happens if the energy of the vibrational mode equals the energy gap between the filled and empty levels. Electrons then flow through the protein and reduce the disulfide bridge via a zinc ion, thus releasing the G-protein for further transduction steps.

    If there is a molecule between the electron source and electron sink, and if that molecule vibrates then (taking the energy of the vibrational quantum as E) indirect tunneling can occur by an additional channel if there is an energy level in the source with energy E above that in the sink. After tunneling, the molecule will have a vibrational energy higher by E. In other words, tunneling occurs only when a molecular vibrational energy E matches the energy difference between the energy level of the donor and the energy level of the acceptor. The receptor then operates as a spectrometer which allows it to detect a single well-defined energy, E . If the change in energy between donor and acceptor levels is sufficiently large, tunneling current flows across the device only when a molecule with the appropriate vibrational energy is present in the gap. If there are several vibrational modes, which one(s) get excited will depend on the relative strengths of the coupling, and that may be expected to depend, among other things on the partial charges on the atoms and the relative orientation of the charge movements with respect to the electron tunneling path.\"

    While Turin’s theory has not been validated, it seems quite plausible. However, even if generally valid, it does not necessarily mean that the \"Steric Theory\" doesn’t play a role.

    [The so-called electron tunneling concept in proteins is a major topic of debate as to the exact mechanism of electron transfer. This stems from the work of Jacqueline Barton (Electron transfer between metal complexes bound to DNA: is DNA a wire?) at the California Institute of Technology.]

    While both the \"Steric\" and \"Vibrational Induced Electron Tunneling Spectroscope\" theories answer many of the questions posed, as one is solved, others arise.

    The Human Vomeronasal Organ (from same document)
    The VNO has been known to be present in human fetuses and has been reported sporadically in adults since the eighteenth century, although many find this improbable. Most of the work on vomeronasal function has been in rodents, snakes and insects where pheromonic chemicals play a communication role in attraction & reproduction. Its presence and function (if it, indeed, functions) in humans has been a matter of debate. Recently, however, Savic et. al. have shown that women smelling an androgen-like compound activate the hypothalamus, with the center of gravity in the preoptic and ventromedial nuclei. Men, in contrast, activate the hypothalamus (center of gravity in paraventricular and dorsomedial nuclei) when smelling an estrogen-like substance. This sex-dissociated hypothalamic activation suggests a potential physiological substrate for a sex-differentiated behavioral response in humans. Whether this provides indirect (or direct) evidence of VNO like descrimination in humans remains to be seen.

    Recently, Mombaerts, Greer and co-workers, showed that the human genome contains at least one gene found in epithelial tissue in the nasal that closely resembles a family of mouse pheromone receptors—genes that are primarily involved in detecting odorless chemicals such as pheromones. \"Until this report,\" Greer states, \"the consensus was that humans do not have receptors that belong to this family of genes. Now the door is open to reconsidering the functional organization of the human olfactory system.\" Mombaerts doesn\'t rule out the possibility that more pheromone receptors will turn up in sequence data in the future, but he is confident that only a few more, if any, will emerge.

    ---------------------

    http://www.healthlibrary.com/news/news22dec/story9.htm
    That it is physically separate was very unkindly shown with some mice; knock the sexual nose of the mouse out, it can still smell but cannot mate. We humans have a vestige of the vomeronasal organ in us, but it is by and large inactive.
    :
    :
    Quite a bit of work has gone down the vibrational path, but here too there is a problem. The first one is about the optical isomers that we talked about earlier. Mirror image molecules have identical vibrational spectra! Secondly one can substitute the hydrogen atoms in a molecule with its isotope called deuterium (which has twice the mass as hydrogen has identical chemical properties). Isotopically substituted compounds have different vibrational spectra but the same odour. We thus have a problem. The two major theories of olfaction the size and shape theory and the vibrational spectrum theory - seem inadequate.

    It is at this stage that Dr. Luca Turin of the Department of Anatomy at the University College of London has come up with a new idea. This idea attempts to fuse the shape idea and the vibration theory. It suggests that the receptor molecules themselves might act as a vibrational spectroscope.

    ---------------------

    http://community-2.webtv.net/essentialhealth/AROMATHERAPY/
    Through the use of chemistry plants can talk to each other, defend against predators and attack other species to protect their resources. Possibly this explains why trees can live and adapt over many generations, some living for over 2000 years. When under attack trees produce a chemical tannin which can be detected (Professor Wouter Van Hoven\'s work in Africa) within 15 minutes. These tannins showed up as an increase in the leaves within an hour. It took 24 to 100 hours after the attack before the trees returned to their normal chemical state. The trees also let other trees in the area know about the attack, presumably by an airborne chemical messenger or hormone. They thought these messages were sent by air since an increase of tannins was noted in other trees which were not under direct attack and were not connected by their root systems to the original trees.

    Trees also produce chemicals which insects ingest and leave behind in their droppings. These chemicals prevent other plants from growing nearby and conserves resources for the tree.

    Aroma molecules also give off an infrared radiation that can be picked up by other insects and probably animals and humans. Humans have their own infrared emanations which seem to relate to the subtle molecular odors or pheromones that surround a person. Infrared radiation can also be absorbed. John Tyndale discovered that the essential oils of Patchouli, Sandalwood, Cloves, Lavender, Rose, Lemon, Thyme, Rosemary and Aniseed can absorb infrared rays. These were the oils he experimented with and it is believed other oils have these same capabilities. It is known that infrared exposure improves circulation and opens blood vessels, bringing blood to the surface. This could be why the oils which are also known to absorb infrared radiation can increase circulation and oxygenate the blood.

    Many times just the placement of a hydrogen atom can determine the smell of a compound. All of the components are the same chemically, only in one the hydrogen atom sits to the right, which causes the plane of polarization of light to rotate to the right. In the other it is sitting to the left causing the polarization of light to be to rotate to the left. When this happens identical aroma molecules will be called laevorotary (left) or dextrorotary (right) and each will have a completely different smell. Spearmint (left) and caraway (right) are an example of this and are called stereo-isomers.

    There may be 200 to 800 different chemical constituents in a single oil and each has its own effect on the body. For example, Aldehydes are anti-infectious, sedative and calming to the nervous system. Eugenols are stimulating and antiseptic. Ketones stimulate cell regeneration and liquify mucous. Phenols are antiseptic and kill viruses and bacteria. Sesquiterpenes are anti-inflammatory and bring increased oxygen to the brain and stimulate the endocrine glands, Terpene Alcohols are anti-bacterial and work as diuretics and de-congestants.The list could go on and on.

    :
    :

    The measurable rate of electrical flow between two points is called frequency. Everything has frequency. Scent is created by the rate that molecules move according to Dr. Luca Turin, of University College in London. Dr. Turin is doing work on the vibration rate of aromatic materials. This rate can speed up or slow down, depending on the oil. He believes it is the vibration rate rather than the molecular shape that make oils smell a certain way.

  6. #6
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    Default Re: Question for the Chemists

    We flower children know this. It\'s your vibe, man. You gotta have a good vibe. Been sayin\' it for years. [img]/ubbthreads/images/icons/smile.gif[/img]

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    Default Re: Question for the Chemists

    You feel me?

    [img]/ubbthreads/images/icons/shocked.gif[/img]

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    Default Re: Question for the Chemists

    I can feel you from here. Must be your digital pheromones.

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    Default Re: Question for the Chemists

    Ah yes, the all powerful, non-quantifiable, digimones and vibimones. Gotta love them

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