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Franklin, Rosalind (Elsie)

dna ray structure diffraction

(1920–58) British physical chemist and X-ray crystallographer.

The daughter of prosperous Jewish parents, Franklin studied chemistry and physics at Cambridge and afterwards, as war work, took a job in coal research, studying its pore size and properties as a solid colloid and being awarded a PhD for this in 1945. Then, during a happy period of 4 years in Paris at the Sorbonne, she moved from physical chemistry to X-ray diffraction, using this method to study colloidal carbon.

Armed with this new skill, she moved in 1951 to join the biophysics group at King’s College, London, to extend the X-ray diffraction work there. Soon she began to use this method on DNA, which was known to have a central place in the mechanism of heredity. In the department M H F Wilkins (1916– ) was already working with DNA, using X-ray and other methods; unhappily, relations between the two were never good. In part, this was because their differing responsibilities in the DNA work at King’s were unclear, a problem for which Sir John Randall, director of the unit, must bear the blame. DNA is a difficult substance to work on; a sticky, colloidal nucleic acid, its precise properties depend upon its origin and history. However, Franklin used her past experience with awkward materials to design an X-ray camera suitable for low-angle reflections, and she used specimens of DNA which were drawn into thin fibres under carefully controlled conditions, notably of hydration. In this way she defined two forms of DNA and obtained X-ray diffraction photographs that showed the DNA to have an ordered, crystalline structure. They were the best X-ray diagrams then obtained for DNA, and she deduced from them that the long, chain-like DNA molecules might be arranged in a helical form, with the phosphate groups on the outside.

X-ray diffraction pattern showing characteristic features derived from a thread of the B-form of DNA. The bold cross-like pattern is characteristic of a helical structure. The spacing between the layer-lines making up the cross, and the angle between the cross arms, relate to the pitch and the climb-angle of the helix respectively. It was a pattern similar to this, obtained by Rosalind Franklin in Wilkins’ lab, which led Watson and Crick to make a double-helical model for DNA in 1953.

Knowledge of her results passed by several routes (some of which have been considered of questionable propriety) to in Cambridge, who were working on the structure of DNA also, mainly by use of model-building methods rather than the experimentation and formalized calculation technique used by Franklin. Her interpretation of her excellent pictures was at times for and at other times against a helical DNA; but after Watson and Crick had formed their inspired view of DNA, her results could be seen to give valuable support to their deductions. Their idea of a double helix structure for DNA also gave pointers to its mode of action in the transfer of genetic information. The famous issue of Nature in April 1953 which proposed their double helix was accompanied by her paper, with R Gosling, supporting their views.

Unhappy at King’s, she moved in 1953 to Birkbeck College, London, again to work with X-rays on biological macromolecules, this time viruses; initially TMV (tobacco mosaic virus, a much-studied subject) and, from 1954, working with Aaron (1926– ), who was to win the Nobel Prize for chemistry in 1982. Again she secured X-ray photographs superior to any obtained previously and used them to show that the TMV virus is not solid, as had been thought, but a hollow tubular structure. Despite being a cancer victim from 1956, she began work on the polio virus.

Her death aged 37 excluded her from consideration for the Nobel Prize for physiology and medicine in 1962, which was shared by Crick, Watson and Wilkins.

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