Letter from Francis Crick to Rosalind Franklin (and notes on two papers by Franklin and Raymond Gosling)


Title:
Letter from Francis Crick to Rosalind Franklin (and notes on two papers by Franklin and Raymond Gosling)
Creator:
Crick, Francis, 1916-2004
Recipient:
Franklin, Rosalind
Date:
5 June 1953
Description:
Crick here discussed the X-ray crystallographic evidence offered by Rosalind Franklin and her doctoral student Gosling on the structure of DNA extracted from calf thymus, specifically on the distinction between the crystalline A form and the paracrystalline, heavily hydrated, longer and thinner B form of DNA, the form which DNA takes before replication and the form that yielded the clearest X-ray evidence for a helical structure. In addition, Crick commented on Franklin's evidence that the position of the sugar-phosphate backbone on the outside of the DNA molecule, where the phosphate atoms can react with hydrogen and become ionized, that is, acquire the electrical charge that turns nucleic acid into an acid.. A final, critical piece of evidence Crick noted was Franklin's determination of the space group of DNA crystals, face-centered monoclinic. Crystallographers group crystals in 230 different space groups according to their symmetry, that is, according to the shape of their unit cell. As Crick realized, crystals in a face-centered monoclinic space group have a dyadic structure, meaning that one half of a structure matches the other half in reverse. Which is to say that if the structure is rotated by 180 degrees, it comes back into symmetry with itself. This crucial evidence, which Franklin herself as well as other researchers in her laboratory failed to appreciate, pointed to a molecule made of two parallel chains running in opposite directions.
Original Repository:
The Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers
Location:
Box: 104. Folder: PP/CRI/I/3/5
Rights:
Reproduced with permission of the Wellcome Library for the History and Understanding of Medicine. and http://library.wellcome.ac.uk/
Genre:
Letters (correspondence)
Notes
Subject:
Crystallography, X-Ray
Format:
Text
Extent:
6 pages
Language:
English
Legacy Source Citation:
Original Repository. Wellcome Library for the History and Understanding of Medicine. Francis Harry Compton Crick Papers. 11646. URL. http://archives.wellcome.ac.uk/
Legacy ID:
SCBBLW
NLM ID:
101584582X162
Profiles Collection:
The Francis Crick Papers
Story Section:
The Discovery of the Double Helix, 1951-1953