Watson&Crick-1953论文---粗译(英汉对照含图)

NatureVOL171,page737.2April1953AStructureforDeoxyriboseNucleicAcid脱氧核糖核苷酸的结构Wewishtosuggestastructureforthesaltofdeoxyribosenucleicacid(D.N.A.).Thisstructurehasnovelfeatureswhichareofconsiderablebiologicalinterest.AstructurefornucleicacidhasalreadybeenproposedbyPaulingandCorey(1).Theykindlymadetheirmanuscriptavailabletousinadvanceofpublication.Theirmodelconsistsofthreeintertwinedchains,withthephosphatesnearthefibreaxis,andthebasesontheoutside.我们想推测出DNA结晶的结构。这些结构有许多新的为很多生物学家所吸引的特点.PaulingandCorey已经提出过核苷酸的一个结构.他们在出版以前慷慨的把他们的手稿给我们看过。他们的模型由三条相互缠绕的链组成，磷酸基团靠近中心轴，而碱基在外面。Inouropinion,thisstructureisunsatisfactoryfortworeasons:我们认为，这个模型有以下两个方面的不足(1)WebelievethatthematerialwhichgivestheX-raydiagramsisthesalt,notthefreeacid.Withouttheacidichydrogenatomsitisnotclearwhatforceswouldholdthestructuretogether,especiallyasthenegativelychargedphosphatesneartheaxiswillrepeleachother.(2)SomeofthevanderWaalsdistancesappeartobetoosmall.1.我们相信是晶体这个材料产生的X-衍射图标，而不是自由的酸。如果没有酸性的氢原子就不能确定什么使这些结构结合在一起。2.一些范德华距离太小Anotherthree-chainstructurehasalsobeensuggestedbyFraser(inthepress).Inhismodelthephosphatesareontheoutsideandthebasesontheinside,linkedtogetherbyhydrogenbonds.Thisstructureasdescribedisratherill-defined,andforthisreasonweshallnotcommentonit.Fraser（在出版社里）曾提出过另一个三链的结构模型。在他的模型中磷酸基团在外面，碱基在里面，他们以氢键连接曾被描述为相当不好的定义，因此我们在这不做评论。Wewishtoputforwardaradicallydifferentstructureforthesaltofdeoxyribosenucleicacid.Thisstructurehastwohelicalchainseachcoiledroundthesameaxis(seediagram).Wehavemadetheusualchemicalassumptions,namely,thateachchainconsistsofphosphatediestergroupsjoiningß-D-deoxyribofuranoseresidueswith3',5'linkages.我们想提出一个根本不同的脱氧核糖核苷酸晶体的结构。这一结构有两条螺旋的链，每条绕着同一中心轴盘绕（如图所示）。我们曾做过普通的化学假定，换句话说，每条链由在3’,5处将磷酸二酯基团加入到脱氧核呋喃糖中。Thetwochains(butnottheirbases)arerelatedbyadyadperpendiculartothefibreaxis.Bothchainsfollowright-handedhelices,butowingtothedyadthesequencesoftheatomsinthetwochainsruninoppositedirections.EachchainlooselyresemblesFurberg's(2)modelNo.1;thatis,thebasesareontheinsideofthehelixandthephosphatesontheoutside.TheconfigurationofthesugarandtheatomsnearitisclosetoFurberg's'standardconfiguration',thesugarbeingroughlyperpendiculartotheattachedbase.Thereisaresidueoneachevery3.4A.inthez-direction.Wehaveassumedanangleof36°betweenadjacentresiduesinthesamechain,sothatthestructurerepeatsafter10residuesoneachchain,thatis,after34A.Thedistanceofaphosphorusatomfromthefibreaxisis10A.Asthephosphatesareontheoutside,cationshaveeasyaccesstothem.这两条链（出了它们的碱基）被双垂线联系到中心轴。两条链都遵循右手螺旋，但是双的螺旋，所以两条链上的院子向相反的方向运动。每条链近似Furberg's的模型1。那就是，碱基在螺旋的里面，磷酸基在外面。糖和它周围原子的结构近似Furberg的标准结构：糖与和它连接的碱基成垂直存在。在这个Z式的螺旋中每3.4A有一个残基。我们假定同一条链上相邻残基之间有36°的角，因此每条链上的结构每十个残基重复一次，也就是每升高34A重复一次。纤维轴上的磷原子的距离为10A。由于磷在螺旋的外面，所以阳离子更容易接触到它们。Thestructureisanopenone,anditswatercontentisratherhigh.Atlowerwatercontentswewouldexpectthebasestotiltsothatthestructurecouldbecomemorecompact.这一结构是一个开放式的结构，并且它的水含量相当高。因为水含量低会致使碱基倾斜，而水含量多会使结构紧凑。Thenovelfeatureofthestructureisthemannerinwhichthetwochainsareheldtogetherbythepurineandpyrimidinebases.Theplanesofthebasesareperpendiculartothefibreaxis.Thearejoinedtogetherinpairs,asinglebasefromtheotherchain,sothatthetwoliesidebysidewithidenticalz-co-ordinates.Oneofthepairmustbeapurineandtheotherapyrimidineforbondingtooccur.Thehydrogenbondsaremadeasfollows:purineposition1topyrimidineposition1;purineposition6topyrimidineposition6.这一结构的新特点是嘌呤和嘧啶碱基将两条链结合在一起。碱基平面与中心轴垂直，它们以成对的方式与另一条链上的单独碱基结合在一起，所以两条链能肩并肩地围绕理想的垂直坐标轴。碱基对必须一边是嘌呤另一边是嘧啶才能结合在一起。氢键以这样的方式成键：第一个嘌呤和第一个嘧啶结合在一起，第6个嘌呤和第6个嘧啶结合在一起。Ifitisassumedthatthebasesonlyoccurinthestructureinthemostplausibletautomericforms(thatis,withtheketoratherthantheenolconfigurations)itisfoundthatonlyspecificpairsofbasescanbondtogether.Thesepairsare:adenine(purine)withthymine(pyrimidine),andguanine(purine)withcytosine(pyrimidine).如果假设配对仅发生在最能发生互变异构的形式（即为酮式而不是烯醇式），我们发现只有特殊的碱基才能成对。这些对是：腺嘌呤和胸腺嘧啶配对，鸟嘌呤和胞嘧啶配对。Thisfigureispurelydiagrammatic.Thetworibbonssymbolisethetwophosphate-sugarchainsandthehorizontalrodsthepairsofbasesholdingthechainstogether.Theverticallinemarksthefibreaxis.这个图片是纯图示性质。两条带象征两个糖-磷酸链，水平棒象征将两条链连接在一起的碱基对。垂直的线象征中心轴Inotherwords,ifanadenineformsonememberofapair,oneitherchain,thenontheseassumptionstheothermembermustbethymine;similarlyforguanineandcytosine.Thesequenceofbasesonasinglechaindoesnotappeartoberestrictedinanyway.However,ifonlyspecificpairsofbasescanbeformed,itfollowsthatifthesequenceofbasesononechainisgiven,thenthesequenceontheotherchainisautomaticallydetermined.换而言之，如果腺嘌呤形成成对的一部分，在另一条链上，我们假定他一定是胸腺嘧啶。鸟嘌呤和胞嘧啶也相似。碱基在一条单链上的顺序没有任何限制。但只有特别的碱基才能成对，就产生了一下结果：如果一条链上的碱基给出了，那么另一条链上的序列就自然确定了。Ithasbeenfoundexperimentally(3,4)thattheratiooftheamountsofadeninetothymine,andtheratioofguaninetocytosine,arealwaysveryclosetounityfordeoxyribosenucleicacid.已经用实验方法证实了脱氧核糖核苷酸中腺嘌呤和鸟嘌呤的数量，鸟嘌呤和胞嘧啶的数目几乎一致。Itisprobablyimpossibletobuildthisstructurewitharibosesugarinplaceofthedeoxyribose,astheextraoxygenatomwouldmaketoocloseavanderWaalscontact.ThepreviouslypublishedX-raydata(5,6)ondeoxyribosenucleicacidareinsufficientforarigoroustestofourstructure.Sofaraswecan