"The structure of DNA - Coldspringharbor"

Date:
[1953]
Reference:
PP/CRI/H/1/13
Catalogue details

Licence: In copyright

Credit: "The structure of DNA - Coldspringharbor". Source: Wellcome Collection.

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    show marked ultra violet and infra red diehroism (Wilkins et aij 1951 , Fraser and fraser 1951), and give good X-ray fibre diagrams. From a preliminary study of these, Wilkins, Franklin and their co-workers at King's College, London (Wilkins et al. 1953? Franklin and Gosling 1953a, b and o) have b e en able to draw certain general conclusions about the structure of DM. Two important facts emerge from their work. They are: (1) Two distinct forms of DM exist » firstly a crystalline fora, Structure A, (Figure 2) which occurs at about 75f> relative humidity and contains approximately 30 f water. At higher humidities the fibres take up more water, increase in length by about 30and assume Structure B (Figure 3). This is a less ordered form than Structure A, and appears to be paracrystalline; that is, the individual molecules are all packed parallel to one another, but are not otherwise regularly arranged in space. In Table 1, we have tabulated some of the characteristic features which distinguish the two forms. The transition from A to E io reversible and therefore the two structures are likely to be related in a simple manner. (2) The crystallo¿rapilic unit contains two poly nucleotide chains . The argument is crystallographic