Time-resolved fluorescence spectroscopy was used to monitor the effects of varying ionic strength on nucleosome core particle structure. Two main methods were used in these studies. First, the fluorescence anisotropy decay of bound ethidium was measured and was shown to reflect the rotational tumbling of the core particle through solution, the longest recovered decay time being a measure of the rotational correlation time of the particle. A rotational correlation time of 165 ns was recovered for the native core particle at 10 mM ionic strength, in excellent agreement with that predicted by hydrodynamic calculations based on the particle's known size and shape. This technique was then used to measure the rotational correlation time of the core particle as a function of ionic strength. Below 1 mM salt the recovered rotational correlation times suggested little change in shape throughout the region of the reversible low salt transition. At very low ionic strengths (below 0.2 mM), where the low salt transition becomes irreversible, the rotational correlation time increased sharply to ~330 ns, suggesting a major change in the core particle structure. Computer modeling was performed to show that this increase was most likely due to a substantial elongation in the core particle structure, to at least a 5:1 axial ratio. At elevated ionic strengths, the rotational correlation time was seen to increase from the initial value of ~165 ns to ~240 ns as the salt concentration was raised from 10 mM to 0.35 M, with further increases being observed only above 0.65 M; we term this initial increase the moderate salt transition. Trypsinization of the core particles to remove the Nterminal histone domains completely abolished the increase, demonstrating that the moderate salt transition as measured by this technique involves the release of these protein domains from the body of the core particle. The second method used involved the measurement of the fluorescence decay of the intrinsic tyrosine residues of the core particle. This decay proved to be very complex, and was best represented by a distribution of lifetimes, suggesting different environments for the tyrosines. This distribution changed as the ionic strength of the solution changed, suggesting the movement of tyrosine residues to differing environments as the particle undergoes the low and moderate salt transitions, as well as the high salt dissociation. / Graduation date: 1993

No description available.

201 leaves : ill., tables, graphs ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Mawson Institute for Antarctic Research, 1977

Typescript (photocopy) / xii, 285 leaves [16] leaves of plates (some col.) : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1982

Typescript (photocopy) / x, 195 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Physics, University of Adelaide, 1980

Typescript (photocopy) / vi, 65 leaves, [7] leaves of plates : ill. ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Physics, University of Adelaide, 1982

Gas phase anion clusters, consisting of solvent molecules hydrogen bonded to halide anions, are characterised by vibrational predissociation spectroscopy using a combination of mass spectrometry and laser spectroscopy. Monitoring changes in the vibrational properties of neutral solvent molecules when they are attached to a halide anion allows one to infer cluster structures. In some cases, the spectra contain rotationally resolved features, so that quantitative structural parameters can be obtained. (For complete abstract open document)

Typescript (photocopy) / x, 195 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Physics, University of Adelaide, 1980

Molecular beam epitaxy (MBE) grown CaF₂-CdF₂ superlattices (SLs) and CaF₂ thin films doped with Eu ions were investigated by laser spectroscopic techniques. Eu ions were selectively doped into CaF₂ layers and were used as an optical probe to the SLs and thin films. Physical properties of the SLs and thin films were inferred from optical transitions of divalent and trivalent Eu centres. The 4ƒ⁶5d → 4ƒ⁷ transition of Eu²⁺ has shown strain dependent peak shifts of the zero phonon line. These shifts were thought to be a result of deformation in the crystal structure primarily due to the lattice mismatch with the Si substrate. Based on the amount of shifts, the strains associated with the MBE samples were calculated. Photoluminescence (PL) bleaching and its recovery of the same transition of Eu²⁺ in SLs were also explored. At low temperature the bleaching is best described as bi-exponential decay. Localisation of the liberated electrons from the 4ƒ⁶5d absorption band was considered for the bleaching effect. It was observed that at elevated temperatures the PL intensity of the 4ƒ⁶5d → 4ƒ⁷ transition was recovered. Combined excitation-emission spectroscopy (CEES) was employed to investigate trivalent Eu centres in SLs. The strong ⁷F₀ → ⁵D₁ excitation and the ⁵D₀ → ⁷F₁ emission of Eu³⁺ were studied. A novel centre, which is assigned as I, of Eu³⁺ in SL was observed and investigated in comparison with the cubic centre (O centre) of Eu³⁺. Relative to the O centre the I centre has shown a strong thickness dependent PL which can be demonstrated with a mono layer (1 ML = 3.15 Å) resolution. Possible transformation of the I centre to the O centre was also observed by additional thermal and UV excitations. The I and the O centres are proposed as the same centre except for having an electron in the vicinity of the I centre.

Thesis (Ph. D.)--University of Washington, 1989. / Vita. Includes bibliographical references (leaves 221-225).