Applications of EPR with an Emphasis on Tau Fibril Structure

<p>Substances containing unpaired electrons have been studied by electron paramagnetic resonance (EPR) for nearly 70 years. With continual development and enhancement of EPR techniques, questions have arisen regarding optimum method selection for a given sample based on its properties. In this work, radiation defects, natural lattice defects, solid organic radicals, radicals in solution, and spin-labeled proteins were analyzed using CW, pulse, and rapid scan EPR to compare methods. Studies of solid BDPA, E' in quartz, N_s⁰ in diamond, and a-Si:H, showed that rapid scan could overcome many obstacles presented by other techniques, cementing rapid scan as an effective alternative to CW and pulse methods.</p> <p>Relaxation times of six nitroxide radicals were characterized from 0.25-34 GHz, guiding synthesis of improved nitroxides for <em>in vivo</em> imaging experiments. Processes contributing to T₁ of DPPH in polystyrene were found through variable temperature measurements at X- and Q-band, resolving previously-reported discrepancies in relaxation properties and providing new insight into this commonly-used standard.</p> <p>In the history of EPR, the study of proteins is relatively new. Double electron-electron resonance (DEER) has emerged as a powerful technique for the study of amyloid fibrils, a class of protein aggregates implicated in a number of neurodegenerative disorders. Microtubule-associated protein tau forms fibrils linked to Alzheimerfs disease through seeded conversion of monomer. Self-assembly is mediated by the microtubule binding repeats in tau, and there are either three or four repeats present depending on the isoform. DEER was used to show that filaments of 3R and 4R tau are conformationally distinct and that 4R fibrils adopt a heterogeneous mixture of conformations. Populations of 4R fibril conformations, which were independently validated using a model system, can be modulated by introduction of mutations to the primary sequence or by varying fibril growth conditions. These findings provided unprecedented insights into the seed selection of tau monomers and established conformational compatibility as an important driving force in tau fibril propagation.</p> <p>Lastly, DEER acquisition was improved through addition of paramagnetic metal to spin-labeled protein, decreasing collection time, and through use of a novel spin label with increased T₂, thereby lengthening the available acquisition window.</p>

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Year dc:date.available

2014

Author dc:creator

• Meyer, Virginia

Contributors dc:contributor

• Martin Margittai, Ph.D.
• Sandra Eaton
• Andrei G. Kutateladze
• Keith Miller
• Daniel Linseman

• Double electron-electron resonance
• DEER
• Electron paramagnetic resonance
• Relaxation time
• Tau
• Biochemistry
• Chemistry

Statement dc:rights

• <p>Copyright is held by the author. User is responsible for all copyright compliance.</p>

Language dc:language

en

Repository record dc:identifier

https://digitalcommons.du.edu/etd/988

OAI identifier oai:identifier

oai:digitalcommons.du.edu:etd-1987