Roguetheoryofsmellgetsaboost 1. Acontroversialtheoryofhowwesmell， whichclaimsthatourfinesenseofodourdependsonquantummechanics， hasbeengiventhethumbsupbyateamofphysicists. 2. CalculationsbyresearchersatUniversityCollegeLondon (UCL) showthattheideathatwesmellodourmoleculesbysensingtheirmolecularvibrationsmakessenseintermsofthephysicsinvolved. 3. Thatsstillsomewayfromprovingthatthetheory， proposedinthemid-1990sbybiophysicistLucaTurin， iscorrect. Butitshouldmakeotherscientiststaketheideamoreseriously. 4. Thisisabigstepforward， saysTurin， whohasnowsetuphisownperfumecompanyFlexitralinVirginia. Hesaysthatsincehepublishedhistheory， ithasbeenignoredratherthancriticized. 5. Mostscientistshaveassumedthatoursenseofsmelldependsonreceptorsinthenosedetectingtheshapeofincomingmolecules， whichtriggersasignaltothebrain. Thismolecularlockandkeyprocessisthoughttoliebehindawiderangeofthebodysdetectionsystems： itishowsomepartsoftheimmunesystemrecogniseinvaders， forexample， andhowthetonguerecognizessometastes. 6. ButTurinarguedthatsmelldoesntseemtofitthispictureverywell. Moleculesthatlookalmostidenticalcansmellverydifferentsuchasalcohols， whichsmelllikespirits， andthiols， whichsmelllikerotteneggs. Andmoleculeswithverydifferentstructurescansmellsimilar. Moststrikingly， somemoleculescansmelldifferenttoanimals， ifnotnecessarilytohumanssimplybecausetheycontaindifferentisotopes (atomsthatarechemicallyidenticalbuthaveadifferentmass)。 7. Turinsexplanationforthesesmellyfactsinvokestheideathatthesmellsignalinolfactoryreceptorproteinsistriggerednotbyanodourmoleculesshape， butbyitsvibrations， whichcanenourageanelectrontojumpbetweentwopartsofthereceptorinaquantum-mechanicalprocesscalledtunnelling. Thiselectronmovementcouldinitiatethesmellsignalbeingsenttothebrain. 8. Thiswouldexplainwhyisotopescansmelldifferent： theirvibrationfrequenciesarechangediftheatomsareheavier. Turinsmechanism， saysMarshallStonehamoftheUCLteam， ismorelikeswipe-cardidentificationthanakeyfittingalock. 9. Vibration-assistedelectrontunnellingcanundoubtedlyoccuritisusedinanexperimentaltechniqueformeasuringmolecularvibrations. Thequestioniswhetherthisispossibleinthenose， saysStonehamscolleague， AndrewHorsfield. 10. StonehamsaysthatwhenhefirstheardaboutTurinsidea， whileTurinwashimselfbasedatUCL， Ididntbelieveit。 But， headds， becauseitwasaninterestingidea， IthoughtIshouldproveitcouldntwork. Ididsomesimplecalculations， andonlythenbegantofeelLucacouldberight. NowStonehamandhisco-workershavedonethejobmorethoroughly， inapapersoontobepublishedinPhysicalReviewLetters. 11. TheUCLteamcalculatedtheratesofelectronhoppinginanosereceptorthathasanodorantmoleculeboundtoit. Thisratedependsonvariousproperties
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