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

Thesis (M.S.) in Chemistry--University of Maine, 2004. / Includes vita. Includes bibliographical references (leaves 46-48).

Thesis (Ph.D.)--Tufts University, 1999. / Adviser: Jonathan E. Kenny. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D.)--University of Washington. / Includes bibliographical references.

Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (leaves 143-151). Also available via World Wide Web.

Thesis (Ph.D.) -- McMaster University, 1999. / Includes bibliographical references (leaves 41-48). Also available via World Wide Web.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 11, 2008) Includes bibliographical references.

Thesis (M.S.) in Oceanography--University of Maine, 2008. / Includes vita. Includes bibliographical references (leaves 64-67).

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Patrik R. Callis. Includes bibliographical references (leaves 38-42).

Thesis (Ph. D.)--Colorado State University, 2004. / Includes bibliographical references.