Two exciting developments can be reported: the launch of the Foundations of Modern Genetics project by the Wellcome Library, and a new accession of Maurice Wilkins material at King's College.
The soft launch of the new Wellcome Library site has taken place - the site includes an exciting new media player that allows users to view books and archive documents and zoom into details. Further developments and addition of new content is ongoing prior to the formal launch of the site in spring 2013. Visit the Wellcome site for more information: http://library.wellcome.ac.uk/about-us/projects/digitisation/foundations-of-modern-genetics-project/
Yesterday we took custody of a new accession of material from Maurice Wilkins' family, including books, some original notebooks predating his DNA studies, photographs of his social and political work, including CND and disarmament rallies, and some original equipment and artefacts and X-ray diffraction images dating from the early 1950s. The new accession is a reminder that much valuable material relating to the history of groundbreaking DNA and genetics research remains to be discovered and made available to researchers. We will keep you posted with more detail on the contents of the new accession as repackaging and listing takes place.
C-configuration of DNA
"The X-ray studies show that DNA molecules are remarkable in that they adopt a large number of different conformations, most of which can exist in several crystal forms (Wilkins, p139 Nobel Prize Lecture)"
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| Title page of typescript showcasing new conformation of DNA (ref: K/PP178/2/78) |
Molecules can have the same chemical structure but can be arranged with a different structure. The different three-dimensional structure affects how the molecule behaves. DNA is no exception: In the later stages of the DNA work, 1952-1953, A and B DNA configuration showed similar properties through the respective x-ray diffraction patterns, however the B-DNA conformation always showed a clearer helical configuration. These observed variations moved the research work away from focusing on a purely helical structure.
The different conformations of the DNA molecules were due to the various crystal forms produced using various different salts of DNA. In the case of the C-configuration of DNA the conformation was obtained using a lithium DNA salt. Whilst, the B-configuration of DNA represented the DNA Double Helix that is present within living cells these new configurations were still important for the structural research undertaken on DNA as Wilkins explained in his Nobel Prize speech:
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| C-form DNA (ref: K/PP178/2/78) |
‘Comparison of the forms provides further confirmation of the correctness of the structures. In a way, the problem is like trying to deduce the structure of a folding chair by observing its shadow: if the conformation of the chair is altered slightly, its structure becomes more evident.’ (Wilkins, p139)
The C-configuration has a 9 ⅓ nucleotide pair per turn compared to the B-configuration with 10 ½ nucleotides per turn. Both are a semi-crystalline structure showing clear helical packing and therefore the two are very similar compared to the crystalline A-configuration. However, whilst B-configuration is found in nature the C-configuration was an artefact formed by the drying process.
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| C-form DNA (ref: K/PP178/2/78) |
To read more about the C-configuration of DNA and the later research on the structure of DNA undertaken by the KCL Biophysics Department, you can visit the Wellcome Digital Library where this file along with many others have been digitised and is freely available online here.
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