"A Structure for DNA"

Date:
[1953]
Reference:
PP/CRI/H/1/11/3
Catalogue details

Licence: In copyright

Credit: "A Structure for DNA". Source: Wellcome Collection.

    A STRI'CTCRS FOR £»IS»A. Pauling and Corey 1 have recently proposed a structure for nucleic acid, They kindly nade their manuscript available to us in advance of publication* In our ©pinion their e true tur e is unsatisfactory for two reasons s 1, We believe that the material which gives the X-ray diagram# is the salt, not the free seid* Without the acidic hydrogen atom® it is not olear what forces would hold the structure together, especially as the negatively charged phosphate© near the axis will repel each other» 2« Some of the van der »'aal® distances api ear to be too errali» we wish to put forward e radically different structure for the salt of desoxyribose nucleic acidi (D.N.A,). This structure has two helical chains each coiled round the same axis» The tv<-o chains (but not their bases) are related by a dyad -perpendicular to this axis» Both chains folio* right-handed helices, but owing to the dyed the sequences of the atoas in the two chain® run in opposite direction®» Kaeh chain loosely resembles Purberg*s^ model le«l; that is, the bases are on the inside of the helix and. the phosphates on the outside* The configuration of the sugar and the atoms near it is close to Purberg*® standard configura tion, the sugar being roughly perpendicular to the attached ease. There is a residue on each chain every 3*4 I in the z direction« We have assumed an angle of 36° between adjacent residues in the sa ire chain, so that the structure repeats after 10 residues on each chain, that is, after 3k 1# The distance of a phosphorus atoro from the fibre axis is 10 $.