Greenall, Robert James (1982) X-ray diffraction and molecular modelbuilding studies on the deoxyribonucleic acid double helix. Doctoral thesis, Keele University.

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Abstract

The known nucleic acid conformations and the methods by which they are determined using X-ray fibre diffraction are reviewed and discussed. A new stacking scheme for Watson-Crick base-pairs is described and a left-handed model of B-DNA which incorporates this scheme is presented and evaluated. This model is less successful than the conventional B-DNA model in explaining the observed diffraction pattern. The side-by-side of B-DNA is criticised in detail and its predicted diffraction pattern is found to compare unfavourably with that predicted by the double helix. Two forms of Patterson function have been applied to several data sets. The results suggest both that the accepted A-DNA indexing of Fuller et al (1965) is preferable to a new scheme proposed by Saslsekharan, Bansal and Gupta (1981) and also that a left-handed model of D-DNA may be in better agreement with the observed diffraction pattern than is the right-handed model of Arnott et al (1974) but neither function is found to be sufficiently robust to enable reliable conclusions to be drawn concerning molecular conformation. Expressions are derived which describe the effect on the Patterson functions of baseline errors 1n the measurement of Intensities in diffuse patterns. The conformation and transitions of a bacteriophage DNA have been studied and a model is presented which explains the observed behaviour 1n terms of a groove-bridging putrescinyl linkage. Several models (incuding a preliminary coiled-coil model) of the structure of DNA under mechanical tension are described and compared with the observed diffraction patterns.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QC Physics
Divisions: Faculty of Natural Sciences > School of Chemical and Physical Sciences
Contributors: Fuller, Watson (Thesis advisor)
Depositing User: Lisa Bailey
Date Deposited: 16 Oct 2019 10:59
Last Modified: 16 Oct 2019 10:59
URI: https://eprints.keele.ac.uk/id/eprint/7038

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