Amino Acids and the Asymmetry of Life: Caught in the Act of Formation (Advances in Astrobiology and Biogeophysics) PDF
Preview Amino Acids and the Asymmetry of Life: Caught in the Act of Formation (Advances in Astrobiology and Biogeophysics)
Amino Acids and the Asymmetry of Life Advances in Astrobiology and Biogeophysics springer.com This series aims to report new developments in research and teaching in the inter- disciplinaryfieldsofastrobiologyandbiogeophysics.Thisencompassesallaspects of research into the origins of life – from the creation of matter to the emergence of complex life forms – and the study of both structure and evolution of planetary ecosystemsunderagivensetofastro-andgeophysicalparameters.Themethodscon- sideredcanbeoftheoretical,computational,experimentalandobservationalnature. Preferencewillbegiventoproposalswherethemanuscriptputsparticularemphasis on the overall readability in view of the broad spectrum of scientific backgrounds involvedinastrobiologyandbiogeophysics. Thetypeofmaterialconsideredforpublicationincludes: • Topicalmonographs • Lecturesonanewfield,orpresentinganewangleonaclassicalfield • Suitablyeditedresearchreports • Compilations of selected papers from meetings that are devoted to specific topics The timeliness of a manuscript is more important than its form which may be un- finished or tentative. Publication in this new series is thus intended as a service to the international scientific community in that the publisher, Springer-Verlag, offers global promotion and distribution of documents which otherwise have a restricted readership.Oncepublishedandcopyrighted,theycanbedocumentedinthescientific literature. SeriesEditors: Dr.AndréBrack Dr.ChristopherP.McKay CentredeBiophysiqueMoléculaire NASAAmesResearchCenter CNRS,RueCharlesSadron MoffetField 45071Orléans,Cedex2,France CA94035,USA [email protected] Dr.GerdaHorneck Prof.Dr.H.Stan-Lotter DLR,FF-ME InstitutfürGenetik RadiationBiology undAllgemeineBiologie LinderHöhe UniversitätSalzburg 51147Köln,Germany Hellbrunnerstr.34 [email protected] 5020Salzburg,Austria Uwe Meierhenrich Amino Acids and the Asymmetry of Life Caught in the Act of Formation WithaForewordbyHenriB.Kagan 123 Prof.Dr.UweMeierhenrich Universite´ deNice-SophiaAntipolis Faculte´ desSciences CNRSUMR6001 ParcValrose 06108Nice France [email protected] ISBN:978-3-540-76885-2 e-ISBN:978-3-540-76886-9 LibraryofCongressControlNumber:2008930865 (cid:2)c 2008Springer-VerlagBerlinHeidelberg Thisworkissubjecttocopyright.Allrightsarereserved,whetherthewholeorpartofthematerialis concerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,recitation,broadcasting, reproductiononmicrofilmorinanyotherway,andstorageindatabanks.Duplicationofthispublication orpartsthereofispermittedonlyundertheprovisionsoftheGermanCopyrightLawofSeptember9, 1965,initscurrentversion,andpermissionforusemustalwaysbeobtainedfromSpringer.Violationsare liabletoprosecutionundertheGermanCopyrightLaw. Theuseofgeneraldescriptivenames,registerednames,trademarks,etc.inthispublicationdoesnotimply, evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevantprotectivelaws andregulationsandthereforefreeforgeneraluse. Coverdesign:eStudioCalamarS.L. Printedonacid-freepaper 9 8 7 6 5 4 3 2 1 springer.com forEva Foreword Abookonaminoacidsinthecontextoftheoriginoflifeandlife’shomochirality is unusual. Professor Meierhenrich has written a very detailed scenario on the at- tempts of scientists to propose hypotheses taking into account the stereochemical informationgiven bytheanalysisof organic molecules. Onekey tool referstothe famous statement of Louis Pasteur in his lectures: “Optical activity is a signature oflife”. Theauthorpresentsmanyfacetsofthechemicalandphysicalprocessesinvolved onearthorinspaceandheentersintoafascinatingareaofongoingscientificdebate. Attimesthediversityofthetopicsinvolvedmightbedemandingforundergraduates or newcomers to the field, but the book, while challenging, illuminates the way science is progressing among a wide diversity of techniques, scientific areas, and hypotheses. WhenIstartedpreparingmyPh.D.thesisattheColle`gedeFranceinParisunder the supervision of Dr. Jean Jacques, I was attracted by the possibility of deducing the shape of molecules, including their absolute configuration, from experimental data, either spectroscopic or chemical. Organic chemistry remained strongly con- nectedtopharmaceuticalchemistry,wheremanycompoundsofbiologicalinterest areasymmetricandopticallyactive.ThemanipulationofmolecularmodelsasDrei- dingmodels(therewerenocomputersatthattime)allowedforanalysingthethree- dimensionalbehaviourofmanyrigidormobilestructures.Conformationalanalysis ofcyclohexaneandpolycyclicsystemssuchassteroidshavebeenrecentlyrational- izedbyD.H.RBartonandO.Hassel(Nobelprizewinnersin1969).Theprediction ofthestericcourseofreactionsthatcreateanewasymmetriccenterbecamepossible andwasbasedonsimpleconcepts.AftermyPh.D.,Iwasinvolvedinafruitfulcol- laboration with Prof. Alain Horeau, Head of the Organic Chemistry Laboratory at theColle`gedeFrance.Heproposedachemicalmethodtoestablishtheabsolutecon- figurationofanasymmetriccenterofsecondaryalcoholsRCHR(R’)OHaswellas deuteratedprimaryalcoholsRCHD(R)OH.Iwasassociatedwiththelatestdevelop- mentsoftheHoreau’smethod.Later,Istarted,alwaysinassociationwithA.Horeau, toapproachthedifficultproblemofefficientlycreatinganasymmetriccenterinan achiral molecule (asymmetric synthesis). For that purpose, we used chiral auxil- iaries temporarily connected to a substrate or a reagent. Especially successful was anasymmetricsynthesisthatprovidedalmostenantiomericallypureasparticacid. vii viii Foreword When I became scientifically independent, I launched two completely different projectssimultaneouslyinOrsay.Onewastheexplorationofasymmetriccatalysis usingchiraltransitionmetals.Theotherwastorevisittheoldquestionoftheuseofa chiralphysicalagentsuchascircularlypolarizedlight(CPL),alreadysuggestedby PasteurandLeBelin1860–1874.Inasymmetriccatalysis,wemadeimportantdis- coveriesinthe1970sbydevisingchiralligands(C -symmetricchiraldiphosphines) 2 forrhodiumcomplexes.Thesenewcatalystsallowedpreparationofα-aminoacids by asymmetric hydrogenation with up to 80% enantiomeric excess (e.e.), values whichwerethehighestatthattime.Nowadays,someenantioselectivecatalystsare usedinindustrytopreparechiralcompoundswith99%e.e. Oursecondprojectwasmoreinlinewiththetopicofthepresentbook.Thepres- ence of circularly polarized light, a chiral agent, has been suggested to be present when the prebiotic soup started to produce biomolecules. Pasteur, Le Bel, van’t Hoff, Cotton, Kuhn, and many others considered this possibility seriously, but it wasW.Kuhn,who,in1929–1930,firstperformedapartialasymmetricphotolysis ofaracemiccompound(N,N-dimethylα-azidopropionamide).Therecoveredma- terialwasopticallyactive,althoughofverysmalle.e.Thiscaseofkineticresolution wasnotfollowedbyotherexamplesuntil1974,whenweclearlyshowedthatkinetic resolutionofcamphorcanbecarriedoutwithCPLandaffordedrecoveredcamphor with 20 % e.e. at high conversion. The key factor for a successful experiment is toselectacompoundwithagoodgfactor(g=∆ε/ε).Laterseveralgroupsestab- lishedthatCPLcanalsobeusedtoperformsimilarexperimentsonaminoacids.In 1971,wedescribedthefirstexampleofanasymmetricsynthesisbyusinganachiral substrate and CPL. A photolytic cyclization gave rise to hexahelicene, which was slightly enriched in one enantiomer. This was easy to measure with a polarimeter because hexahelicene has a huge specific rotation. With regard to the question of whether CPL is able to produce optically active compounds, we learned that the answer is “yes”. But what is its prebiotic significance? This question still remains unanswered. We were also involved in a third project that may be of interest for prebiotic chemistry:theamplificationofasmallenantiomericexcessbycatalyticorstoichio- metricmethods.Infact,weshowedin1986thatitispossibletouseanenantioim- purecatalysttocreateaproductofhigherenantiomericexcessthantheoneofthe catalyst.Thiseffectwasnamedthe“nonlineareffect”anditcanbeusefulinauto- catalyticreactions.In2007,weestablishedexperimentally,asproposedbyI.Ugiin 1977,thatsomeracemicreagentscanincreasethee.e.ofpartiallyresolvedsamples thankstoaselectivedestructionofsomeracemiccontentinthesamples. Thepresentbookdiscussesmanywaystoinitiateordevelopopticalactivityfrom achiral or racemic materials. The outlined space exploration and the study of chi- ral molecules are certainly of great interest to better understand the origin of ho- mochirality of biological systems. The underlying problem, however, may remain unsolved for a long period of time, if not forever. The scientific subject is intel- lectually appealing, and it has great potential for attracting young people towards chemistryaswellasthephysicalandnaturalsciences. Orsay,France HenriB.Kagan May2008 “Now,ifyou’llonlyattend,Kitty,andnottalksomuch,I’ll tellyouallmyideasaboutLooking-glassHouse.First,there’s theroomyoucanseethroughtheglass–that’sjustthesame asourdrawingroom,onlythethingsgotheotherway.Ican seeallofitwhenIgetuponachair–allbutthebitbehindthe fireplace.Oh!IdosowishIcouldseethatbit!Iwantsomuch toknowwhetherthey’veafireinthewinter:younevercan tell,youknow,unlessourfiresmokes,andthensmokecomes upinthatroomtoo–butthatmaybeonlypretence,justto makeitlookasiftheyhadafire.Wellthen,thebooksare somethinglikeourbooks,onlythewordsgothewrongway;I knowthat,becauseI’vehelduponeofourbookstotheglass, andthentheyholduponeintheotherroom.” “HowwouldyouliketoliveinLooking-glassHouse, Kitty?Iwonderifthey’dgiveyoumilkinthere?Perhaps Looking-glassmilkisn’tgoodtodrink–Butoh,Kitty!nowwe cometothepassage.Youcanjustseealittlepeepofthe passageinLooking-glassHouse,ifyouleavethedoorofour drawing-roomwideopen:andit’sverylikeourpassageasfar asyoucansee,onlyyouknowitmaybequitedifferenton beyond.Oh,Kitty!howniceitwouldbeifwecouldonlyget throughintoLooking-glassHouse!I’msureit’sgot,oh!such beautifulthingsinit! Let’spretendthere’sawayofgettingthroughintoit, somehow,Kitty.Let’spretendtheglasshasgotallsoftlike gauze,sothatwecangetthrough.Why,it’sturningintoasort ofmistnow,Ideclare!It’llbeeasyenoughtogetthrough”– Shewasuponthechimney-piecewhileshesaidthis,though shehardlyknewhowshehadgotthere.Andcertainlytheglass wasbeginningtomeltaway,justlikeabrightsilverymist. InanothermomentAlicewasthroughtheglass,andhad jumpedlightlydownintotheLooking-glassroom.Thevery firstthingshedidwas... LewisCarrollin ThroughtheLooking-Glass,andWhatAliceFoundThere ix Preface The story of this book begins with the question “How did life originate and why were left-handed molecules selected for its architecture?” It is widely known that in processes triggering the origin of life on Earth, the equal occurrence, the parity betweenleft-handedaminoacidsandtheirright-handedmirrorimages,isviolated. The balance is inevitably tipped to the left – provoking that life’s proteins today exclusivelyimplementtheleftformofaminoacids. Whytotheleft? Ifwererunthetapeoflife’sorigin,wouldweoncemoreobtaintoday’slifeusing the left form of amino acids? Can’t we think of mirror image life made of right- aminoacids?DidmirrorimagelifeexistonEarthordoesitexistsomewhereelse? Whatwouldmirrorimagelifelooklikeandhowwoulditinteractwiththeenviron- mentandwithus?Puzzlingquestionsofthiskindcontributedtotheawakeningof publicinterestinsymmetry,thehypotheticalexistenceofmirrorimagelife,andits properties. Symmetry phenomena like these made also me curious and I began to separatemoleculesfromtheirmirrorimageforms. After several attempts, we were lucky to be engaged in the construction of the “Chirality-Module” of the ambitious cometary mission ROSETTA, an instrument designedtolandonacometandsearchformoleculesandtheirmirrorimageforms. Theideaistotracetheoriginoflife’sleft-handednessbacktoouterspace. Indeed,whenweproducedacometanalogueinthelaboratory,wefoundawide variety of amino acid molecules and their mirror image forms therein. The results supportednotonlytheconceptoftheextraterrestrialdeliveryofprebioticmolecules triggeringtheappearanceoflifeonEarth,nowwell-knownandhighlycited,butit provided a source of motivation in devoting an entire book to all the fascinating phenomenarelatedtotheasymmetryoflifeanditsorigin. Itisprobablytruethatmostscientistsaresolvingmoreappliedproblemsinbi- ology, chemistry, physics, and mathematics. But we should always be alert to the greatproblems,suchasunderstandingtheprocessesleadingtotheoriginoftheone- handednessoflife.Givenpastexperience,suchgreatquestionswillbesolved–not bychancebutbythepreparedmind(Penny2006).Thisbookaimstobeastarting xi
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