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Title: Electron paramagnetic resonance studies of spin-labelled ethidium bromide DNA interactions
Author: Keeble, David James
Awarding Body: Keele University
Current Institution: Keele University
Date of Award: 1986
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Spin-Labelled Ethidium Bromide (SLEB) was prepared in order to study its interactions with natural DNA in the form of fibres . The technique of electron paramagnetic resonance was used in this thesis. Knowledge of the conformational transition pathway of natural DNA for given counterion concentration as a function of relative humidity was utilised in the study of effect DNA confomation on the binding of SLEB. To aid interpretation of the results the relevant background material was reviewed. In order to attempt to extract geometric information on binding computer ERR lineshape simulations were used. To facilitate this a microcomputer spectrometer control system was designed and implemented. This allowed spectra to be acquired in digital form and transfered to the mainframe computer. Two schemes for magnetic field control were investigated, one based on a commercial NMR magnetometer, and a superior pulsed NMR field locking magnetometer developed in this laboratory. In order to obtain lineshapes undistorted by dipolar broadening it is advantageous to use fibres with a high phosphate to drug ratio (P/D), however spectrometer sensitivity becomes a limiting factor. A review of noise in spectrometer systems is included. The use of a microwave low-noise preamplifer to reduce the system noise figure was investigated. An attempt to construct a loop-gap resonator was made and justified theoretically. A 35GHz spectrometer was constructed and a cavity designed and built to allow the humidity to be varied. The system was made compatible with the control system. Spectra recorded and simulated at this frequency should help confirm those obtained at 9GHz. The results obtained from P/D«70 fibres with a 0.5mM NaCl concentration show the SLEB is in a disordered state from 33% to 75% relative humidity. Spectral changes occur in the range 75% to 98% consistant with intercalation. In this humidity range a transition to the B-form is expected.
Supervisor: Slade, E. F. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics