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 ''The following obituary was contributed by Professor Sir Aaron Klug: 

 

 ""Franklin, Rosalind Elsie (1920-1958), crystallographer, was born at Chepstow Villas, Notting Hill, London, on 25 July 1920, the elder daughter and second of the family of five children of Ellis Arthur Franklin (1894–1964), merchant banker of London, and his wife, Muriel Frances Waley (1894–1976). Both parents came from established Anglo-Jewish families; Helen Bentwich (Labour chairman of the London county council, 1956–7) was her aunt; Herbert Samuel, Viscount Samuel (Liberal politician and first high commissioner for Palestine) was her great-uncle; Arthur Waley (translator of oriental literature) was her mother's cousin. From 1932 to 1938 Rosalind was a scholar at St Paul's Girls' School and went on to Newnham College, Cambridge, where she read natural sciences, taking her part two in chemistry in 1941. Wartime constraints made her time at Cambridge austere and directed her PhD to an industrial problem with the Coal Utilisation Research Association (CURA), while also burdening her with duties as a London air raid warden. 

 

 At CURA Franklin worked on cokes and chars. She found that, although the total volume of the pores in such material increases with increasing temperature, their accessibility decreases. She showed this by a series of ingenious experiments in which, finally, even gaseous helium molecules are unable to penetrate the material. She realized that to reach an understanding of the internal structure of coals and chars it was necessary to use X-ray diffraction methods and these she learned when she moved in 1947 to the Laboratoire Centrale des Services Chimiques de l'État in Paris, where she was employed as a chercheur of the Centre National de la Recherche Scientifique. These were personally happy years for her and scientifically very productive. She learned, and improved, X-ray techniques for dealing quantitatively with substances of limited internal order, which presented much more difficulty than the highly ordered crystals which the X-ray crystallographers of the day were more familiar with. In a series of beautifully executed investigations Franklin discovered the fundamental distinction between chars that turned into graphite on heating and those that did not, and further related this difference to the chemical constituents of the material from which the chars were made. These results later proved to be highly relevant for the development of carbon fibres, materials of industrial importance which are made of rolled up parallel sheets of graphite layers. 

 

 The combination of these X-ray analytical techniques with chemical preparatory skill attracted the attention of others, and in 1950 Franklin was invited by John Randall to build up an X-ray diffraction laboratory at King's College, London, for the purpose of studying the structure of DNA. She accepted, and started work in January 1951 as a Turner and Newall research fellow of London University. Although DNA is now almost a household word, at that time it was not at all clear, despite Avery's great paper of 1944, that it was the hereditary substance itself, and certainly no one, not even Crick and Watson, who finally solved its double helical structure, suspected that the three-dimensional structure itself would point to a direct conclusion on how genes replicated themselves. (The crucial feature of the structure of DNA is not the double helical arrangement of the two phosphate sugar backbones, but the unique pairing of the heterocyclic bases projecting from each of these two strands. It means that each strand is complementary to the other so that, when the two come apart, each can be used to assemble a duplicate of its former partner.) In 1950 DNA was only known to be an important chemical constituent of the chromosomes of the cell nucleus, but that it alone carried the genetic information, irrespective of the protein constituents, was not generally accepted by biochemists. 

 

 Work on DNA at King's had been begun by M. H. F. Wilkins who, before 1951, together with a research student, R. G. Gosling, had succeeded in obtaining well-orientated fibres of the long DNA macromolecules, which showed a higher degree of crystallinity, as judged by the X-ray diffraction pattern, than specimens produced by earlier workers. Franklin was asked by Randall to undertake a systematic X-ray study of DNA fibres and Gosling was placed under her supervision. Randall left an unfortunate ambiguity about the respective positions of Wilkins and Franklin which later led to dissension about the demarcation of the DNA research at King's, but a letter of his to Franklin in 1950 makes it clear that on 'the experimental X-ray effort there would be for the moment only yourself and Gosling'. 

 

 Within the first year Franklin transformed the state of the fiel