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20 November 1953 |
|Known for||Vibration theory of olfaction|
Vibration theory of olfaction
A major prediction of Turin's vibration theory of olfaction is the isotope effect: that the normal and deuterated versions of a compound should smell different due to unique vibration frequencies, despite having the same shape. A 2001 study by Haffenden et al. showed humans able to distinguish benzaldehyde from its deuterated version.
However, experimental tests published in Nature Neuroscience in 2004 by Keller and Vosshall failed to support this prediction, with human subjects unable to distinguish acetophenone and its deuterated counterpart. The study was accompanied by an editorial, which considered the work of Keller and Vosshall to be "refutation of a theory that, while provocative, has almost no credence in scientific circles." It continued, "The only reason for the authors to do the study, or for Nature Neuroscience to publish it, is the extraordinary -- and inappropriate -- degree of publicity that the theory has received from uncritical journalists." The journal also published a review of The Emperor of Scent, calling Chandler Burr's book about Turin and his theory "giddy and overwrought."
Proponents note that the potential presence of a vested interest on the part of large brands and retailers in complex and mystical attitudes towards the production of fragrance substances leaves suspect the dispute over Turin's scientific theory as a means of avoiding a rapid shift in the consumer market which would threaten brand stability and profits.
In addition, tests with animals have shown fish and insects able to distinguish isotopes by smell. Biophysical simulations published in Physical Review Letters in 2007 suggest that Turin's proposal is viable from a physics standpoint.
The vibration theory received possible support from a 2004 paper published in the journal Organic Biomolecular Chemistry by Takane and Mitchell, which shows that odor descriptions in the olfaction literature correlate more strongly with vibrational frequency than with molecular shape.
In 2011, Turin and colleagues published a paper in PNAS showing drosophila fruit flies can distinguish between odorants and their deuterated counterparts. Tests on drosophila differ from human experiments by using an animal subject known to have a good sense of smell and free from psychological biases that may complicate human tests. Drosophila were trained to avoid the deuterated odorant in a deuterated/normal pair, indicating a difference in odor. Furthermore, drosophila trained to avoid one deuterated odorant also avoided other deuterated odorants, chemically unrelated, indicating that the deuterated bond itself had a distinct smell. The authors identified a vibrational frequency that could be responsible and found it close to one found in nitriles. When flies trained to avoid deuterated odorants were exposed to the nitrile and its non-nitrile counterpart, the flies also avoided the nitrile, consistent with the theory that fly olfaction detects molecular vibrations. 
Two years later, in 2013, Turin and colleagues published a study in PLoS ONE showing that humans easily distinguish gas-chromatography-purified deuterated musk in double-blind tests. The team chose musks due to the high number of carbon-hydrogen bonds available for deuteration. They replicated the earlier results of Vosshall and Keller showing that humans cannot reliably distinguish between acetophenone and its deuterated counterpart, with 8 hydrogens, and showed that humans only begin to detect the isotope odor of the musks beginning at 14 deuteriums, or 50% deuteration. Because Turin's proposed mechanism is a biological method of inelastic electron tunnelling spectroscopy, which exploits a quantum effect, his theory of olfaction mechanism has been described as an example of quantum biology.
In response to Turin's 2013 paper, involving deuterated and undeuterated isotopomers of the musk cyclopentadecanone, Block et al. in a 2015 paper in PNAS report that the human musk-recognizing receptor, OR5AN1, identified using a heterologous olfactory receptor expression system and robustly responding to cyclopentadecanone and muscone (which has 30 hydrogens), fails to distinguish isotopomers of these compounds in vitro. Furthermore, the mouse (methylthio)methanethiol-recognizing receptor, MOR244-3, as well as other selected human and mouse olfactory receptors, responded similarly to normal, deuterated, and carbon-13 isotopomers of their respective ligands, paralleling results found with the musk receptor OR5AN1. Based on these findings, the authors conclude that the proposed vibration theory of olfaction does not apply to the human musk receptor OR5AN1, mouse thiol receptor MOR244-3, or other olfactory receptors examined. Additionally, theoretical analysis by the authors shows that the proposed electron transfer mechanism of the vibrational frequencies of odorants could be easily suppressed by quantum effects of nonodorant molecular vibrational modes. The authors conclude: “These and other concerns about electron transfer at olfactory receptors, together with our extensive experimental data, argue against the plausibility of the vibration theory.” In commenting on this work, Vosshall writes “In PNAS, Block et al…. shift the “shape vs. vibration” debate from olfactory psychophysics to the biophysics of the ORs themselves. The authors mount a sophisticated multidisciplinary attack on the central tenets of the vibration theory using synthetic organic chemistry, heterologous expression of olfactory receptors, and theoretical considerations to find no evidence to support the vibration theory of smell." While Turin comments that Block used "cells in a dish rather than within whole organisms" and that "expressing an olfactory receptor in human embryonic kidney cells doesn't adequately reconstitute the complex nature of olfaction...", Vosshall responds "Embryonic kidney cells are not identical to the cells in the nose .. but if you are looking at receptors, it's the best system in the world." In a Letter to the Editor of PNAS, Turin et al. raise concerns about Block et al. and Block et al. respond.
Education and employment
After leaving the CNRS, Turin first held a visiting research position at the National Institutes of Health in North Carolina before moving back to London, where he became a lecturer in biophysics at University College London. In 2001 Turin was hired as CTO of start-up company Flexitral, based in Chantilly, Virginia, to pursue rational odorant design based on his theories. In April 2010 he described this role in the past tense, and the company's domain name appears to have been surrendered.
In 2010, Turin was based at MIT, working on a project to develop an electronic nose related in part on his theories, financed by DARPA. In 2014 he moved to the Institute of Theoretical Physics  at Ulm University where he is currently a Visiting Professor.
Role in the case of Henri Korn
In 1988, Turin began work at the lab led by neuroscience researcher Henri Korn at the Pasteur Institute. There, Turin and his colleague Nicole Ropert reported to their superiors that they believed some of Korn's research on neurotransmitters was based on fabricated results. After Turin made a formal request that the CNRS investigate the allegations, he was told to find work outside of France; Ropert was also asked to leave.
Korn was awarded the prestigious Richard Lounsbery Award in 1992 and became a member of the National Academy of Sciences in the U.S. and the French Academy of Sciences. Then in 2007, re-analysis of Korn's data by Jacques Ninio in the Journal of Neurophysiology showed serious anomalies that suggested the results were indeed fabricated.
Publications and media coverage
Turin is the author of the book The Secret of Scent (2006), which details the history and science of his theory of olfaction, an acclaimed critical guide to perfume in French, Parfums: Le Guide, with two editions in 1992 and 1994, and is co-author of the English-language books Perfumes: The A-Z Guide (2008) and The Little Book of Perfumes (2011). He is also the subject of the 2002 book The Emperor of Scent by Chandler Burr and the 1995 BBC Horizons documentary "A Code in the Nose."
Since 2003, Turin has also written a regular column on perfume, "Duftnote," for NZZ Folio, the German-language monthly magazine of Swiss newspaper Neue Zürcher Zeitung. The column is also published in English on the magazine's website.
- Turin, Luca (1992). Parfums. Le guide (french). ISBN 978-2-86665-163-3.
- Turin, Luca (2006). The Secret of Scent: Adventures in Perfume and the Science of Smell. New York: Ecco. ISBN 0-06-113383-3.
- Turin, Luca; Tania Sanchez (2008). Perfumes: The A-Z Guide - Hardcover. Penguin. ISBN 978-0-670-01865-9.
- Turin, Luca; Tania Sanchez (2009). Perfumes: The A-Z Guide - Paperback (new reviews(~450) and new Top 10 lists). Penguin. ISBN 978-0-143-11501-4.
- Haffenden, L. J. W.; V. A. Yaylayan; J. Fortin (2001). "Investigation of vibrational theory of olfaction with variously labelled benzaldehydes". Food Chemistry (Elsevier) 73 (1): 67–72. doi:10.1016/S0308-8146(00)00287-9. see also 
- Keller, Andreas; Leslie B. Vosshall (2004). "A psychophysical test of the vibration theory of olfaction". Nature Neuroscience (Nature) 7 (4): 337–338. doi:10.1038/nn1215. PMID 15034588.
- "Testing a radical theory". Nature Neuroscience (Nature) 7 (4): 315–315. 2004. doi:10.1038/nn0404-315. PMID 15048113.
- Gilbert, Avery (2003). "The Emperor's new theory". Nature Neuroscience (Nature) 6 (4): 335–335. doi:10.1038/nn0403-335.
- Havens, Barry R.; Meloan, Clifton E. (1995). "The Application of Deuterated Sex Pheromone Mimics of the American Cockroach (Periplneta americana, L.), to the Study of Wright's Vibrational Theory of Olfaction" (PDF). In Charalambous, G. Food Flavors: Generation, Analysis and Process Influence. Elsevier Science. pp. 497–524.
- Hara, J (1977). "Olfactory discrimination between glycine and deuterated glycine by fish". Experientia (Switzerland: Birkhäuser) 33 (5): 618–619. doi:10.1007/BF01946534. PMID 862794.
- Brookes, Jennifer C.; Filio Hartoutsiou; Andrew P. Horsfield; A. Marshall Stoneham (2007-01-16). "Could Humans Recognize Odor by Phonon Assisted Tunneling?". Physical Review Letters (APS) 98 (038101): 038101. arXiv:physics/0611205. Bibcode:2007PhRvL..98c8101B. doi:10.1103/PhysRevLett.98.038101. PMID 17358733.
- Takane, Shin-ya; John B. O. Mitchell (2004). "A structure-–odour relationship study using EVA descriptors and hierarchical clustering". Organic & Biomolecular Chemistry (RSC Publishing) 2 (22): 3250–3255. doi:10.1039/B409802A. PMID 15534702.
- "Flies sniff out heavy hydrogen : Nature News". Retrieved 2013-05-23.
- "Molecular vibration-sensing component in Drosophila melanogaster olfaction". Retrieved 2013-05-23.
- Gane S, Georganakis D, Maniati K, Vamvakias M, Ragoussis N, Skoulakis EMC, Turin L (2013). "Molecular vibration-sensing component in human olfaction." PLoS ONE 8, e55780. doi:10.1371/journal.pone.0055780
- Palmer, Jason. "Quantum biology: Do weird physics effects abound in nature?". BBC. Retrieved 23 May 2013.
- Block E, et al. (2015). "Implausibility of the Vibrational Theory of Olfaction". Proc. Natl. Acad. Sci. USA 112 (21): E2766–E2774. doi:10.1073/pnas.1503054112. PMID 25901328.
- Vosshall LB (2015). "Laying a controversial smell theory to rest". Proc. Natl. Acad. Sci. USA 112: 6525–6526. doi:10.1073/pnas.1507103112. PMID 26015552.
- Everts S (2015). "Receptor Research Reignites A Smelly Debate". Chem.& Eng. News 93 (18): 29–30.
- Turin, L; Gane, S; Georganakis, D; Maniati, K; Skoulakis, EMC (2015). "Plausibility of the Vibrational Theory of Olfaction". Proc. Natl. Acad. Sci. USA 112 (25): E3154. doi:10.1073/pnas.1508035112. PMID 26045494.
- Block E; Jang, S; Matsunami, H; Batista, VS; Zhuang, H (2015). "Reply to Turin et al.: Vibrational theory of olfaction is implausible". Proc. Natl. Acad. Sci. USA 112 (25): E3155. doi:10.1073/pnas.1508443112. PMID 26045493.
- Burr, Chandler (2002). The Emperor of Scent: A Story of Perfume, Obsession, and the Last Mystery of the Senses. New York: Random House. p. 33. ISBN 0-375-50797-3.
- Nina Sinatra, The science of smell, The Tech, MIT, 23 April 2010
- Archive copy at the Wayback Machine. Accessed 21 May 2010
- Butler, Declan (2007-09-13). "Long-held theory is in danger of losing its nerve". Nature 449 (7159): 124–125. Bibcode:2007Natur.449..124B. doi:10.1038/449124b. PMID 17851481.
- de Pracontal, Michel (2007-09-27). "Fraude à l'Institut Pasteur ? Savants au bord de la crise de nerfs". Le Nouvel Observateur (2238): 110.
- "Je leur ai expliqué la situation. J'ai dit que le devoir d'un scientifique était d'établir la vérité et que je m'étais trouvé dans un laboratoire dont le directeur agissait comme un faussaire. On m'a répondu que j'avais cinq jours pour me trouver un autre poste, de préférence hors de France !" (Luca Turin, as quoted by Michel de Pracontal in Le Nouvel Observateur)
- de Pracontal, Michel (2007-09-27). "Fraude à l'Institut Pasteur ? Savants au bord de la crise de nerfs". Le Nouvel Observateur (2238): 108.
- NZZ-Folio, Duftnote (english version)
- The official website for Perfumes: The A-Z Guide contains a short biographical note and links to articles by Luca Turin.
- Luca Turin stopped updating Perfume Notes, his blog in January 2006. - archived posts.
- TED Talk video of Turin explaining the "Science of Scent"