Letter from Jerry Donohue to Francis Crick

Letter from Jerry Donohue to Francis Crick
In his letter Donohue further defended his argument, presented in an article in the September 12, 1969, issue of Science (vol. 165, p. 1091), that Fourier syntheses of X-ray data produced by Maurice Wilkins and others fit a model with alternative base-pairing, not just the canonical A=T and C=G pairs of the Watson-Crick model. In particular, Donohue once again insisted that Fourier syntheses could not conclusively prove any model because this method for inferring the structure of molecules relied on assumptions about the angles of bonds between atoms which were based upon the proposed model of the molecule itself. Donohue saw in this a theoretical fallacy which, as such, could not be used to rule out other molecular structures.. The resolution achieved by contemporary X-ray diffusion techniques--a resolution to about 3 angstroms, as Donohue mentioned--was yet too low to allow for a conclusive proof of Watson's and Crick's model (an angstrom is a measure for the distance between atoms; one angstrom equals one ten-millionth of a millimeter). Such proof was not offered until the late 1970s.. A dyad is a form of symmetry by which one half of a structure matches the other half in reverse, meaning that if the structure is rotated by 180 degrees, it comes back into symmetry with itself. In the case of DNA, evidence for a dyadic structure, produced first by Rosalind Franklin, suggested to Crick that the molecule consisted of two (not, as other researchers had proposed, three) chains, and that the two chains were antiparallel.
2 pages
Date Created:
9 June 1970
Donohue, Jerry (Jerry Donohue)
Crick, Francis, 1916-2004
Original Repository. Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers. 11646. URL. http://archives.wellcome.ac.uk/
Original Repository:
The Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers
Right Type:
Rights Could Not Be Determined - Release
Right Statement:
Courtesy of the Wellcome Library for the History and Understanding of Medicine.
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DNA and Crystallography, X-Ray
Profiles in Science ID:
Letters (correspondence)
Box: 21. Folder: PP/CRI/D/2/11/1