No. 4356 April 25, 1953 NATURE 737

1 NATURE Publishing , , , , ,Gerrard,H;,andJevons,W., ,40,149(1920). Longuet-Higgins, , , ,6,285(1949). VonArx, , ,11(3)(1950).'Ekman, (Stockholm),2 (11)(1905).MOLECULARSTRUCTUREOFNUCLEICAC IDSAS tructureforDeoxyriboseNucleicAcidWEwisht osuggestastructureforthesaltofdeoxyribos enucleicacid( ,). '. ,withthephosphatesnearthefibreaxis, ,thisstructureisunsatisfactoryfortworeas ons:(I)Webelievethatthematerialwhichgive stheX-raydiagramsisthesalt, ,especiallyasthenegativelychargedphospha tesneartheaxiswillrepeleachother.(2)Some ofthevandel' (inthepress).Inhismodelthephosphatesareo ntheoutsideandthebasesontheinside, , (seediagram).

2 Wehavemadetheusualchemicalassumptions,na mely,thateachchainconsistsofphosphatedi- estergroupsjoining~-D-deoxy ribofuranoseresidueswith3',5' (butnottheirbases) , "berg's' ;thatis, 's'standardconfiguration', betweenadjacentresiduesinthesamechain,so thatthestructurerepeatsafter10residueson eachchain,thatis, , , ,asinglebasefromonechainbeinghydrogen-bo ndedtoasinglebasefromtheotherchain, :purineposition1topyrimidineposition1; (thatis,withtheketoratherthantheenolcon- figurations) :adenine(purine)withthymine(pyrimidine), andguanine(purine)withcytosine(pyrimidin e).In~therwords,ifanadenineformsonemembe rofapair,oneitherchain,thenontheseassump tionstheothermembermustbethymine; ,ifonlyspecificpairsofbasescanbeformed,i tfollowsthatifthesequenceofbasesononocha inisgiven.

3 Thattheratiooftheamountsofadeninetothymi ne,andtheratioofguaninetocytosine, ,astheextraoxygenatomwouldmaketoocloseav andel' ,itisroughlycompatiblewiththeexperimenta ldata, , ~ ,includingthecon-ditionsassumedinbuildin git,togetherwithasetofco-ordinatesforthe atoms, , , NATURE Publishing Group1953738 NATUREA pril25, 'sCollege, ( ) ' ,CavendishLaboratory, ,I,.,andCorey, , NATURE ,171,346(1953); ,39,84(1953).2Jo'urberg,S., ,6,634(1952). Chargaff,E.,forreferencesseeZamenhof,S., Brawerman,G.,andChargaff,E., ,9,402(1952). , 'iol.,36,201(1952)., Astbury,W.'1.'., ,NucleicAcid,66( ,1947). Wilkins, :1<'.

4 ,andRandall,J.'1.'., (1953).MolecularStructl,lreofDeoxypentos eNucleicAcids'WHILE thebiologicalpropertiesofdeoxypentosenuc leicacidsuggestamolecularstructurecon-ta ininggreatcomplexity,X-raydiffractionstu diesdescribedhere( ) ,inapreliminaryway,someoftheexperimental evidenceforthepoly-nucleotidechainconfig urationbeinghelical, (althoughthenitrogenbaseratiosalterconsi derably)innucleoprotein,extractedorincel ls, , ,onedeterminedlargelybytheregularspacing ofnucleo-tidesalongthechain, ('structureB'inthefollowingcommunication byFranklinandGosling) ( ).Astburysuggestedthatthestrong3 "-' ,however,arenotduetoarepeatofapolynucleo tidecomposition,buttothechaincon-figurat ionrepeat, "(alsoStokes,unpublished) ,theintensitydis-tributionalongthenthlay erlinebeingproportionaltothesquareofJn, (J02) ,theeffect5beingtoreproducetheintensityd istributionabouttheoriginaroundthenewori gin,onthenthlayerline, ,ifthenucleotideconsistsofaunithavingcir cularsymmetryaboutanaxisparalleltothehel ixaxis, ,ifthenucleotideconsistsofaseriesofpoint sonaradiusatright-anglestothehelixaxis, ~~.

5 ,/.,,.,AA,AA,,~:-AA:----:~AA-+B.:..----. :.~~BB~/"-B~ ,second, radius,themassata l()