PhD defenses.

Implementation of Dynamic Covalent Chemistries for the Physical Enhancement of Polymeric Materials

Abstract: Polymers have become a ubiquitous part of our lives, filling diverse applications ranging from aerospace to children’s toys. With over three hundred million tons of plastics being produced annually, it is crucial to increase their usable lifespan and reduce their relegation to waste. As such, it is necessary to move away from traditional commodity polymers and steer towards new structural designs that resist deterioration and failure. For wider adoption, these new structural designs should be thermally stable, resistant to additives, and resist/repair damage.

Reactive Oxygen Species Formation from Ambient Particles and Their Roles in Chemical Aging

Abstract: Reactive oxygen species (ROS) including hydroxyl radical (OH·), superoxide anion (O2·-), ozone (O3) and oxygenated organic radicals play an important role in atmospheric and physiological processes. Polycyclic aromatic hydrocarbons (PAHs), including benzo[a]pyrene (BaP), are among the most prominent toxic compounds that can be found in indoor and outdoor environments.

Developing Macrocyclic β-Hairpin Peptide Mimics to Elucidate the Structures of Aβ Oligomers in Alzheimer’s Disease

Abstract: The oligomers formed by the β-amyloid peptide Aβ are unstable and exhibit significant variation in their stoichiometry and structure. This variation complicates efforts to understand how Aβ oligomers affect neurodegeneration associated with Alzheimer’s disease. Frustratingly, high-resolution structures of the oligomers formed by full-length Aβ have largely remained elusive.

Cobalt-Catalyzed Hydrogen Atom Transfer-Initiated Radical–Polar Crossover Alkene Hydrofunctionalizations

Abstract: Chapter 1 contains a thorough overview of cobalt-catalyzed hydrogen atom transfer (HAT)-initiated alkene hydrofunctionalizations with special attention given to radical–polar crossover reactions. The chapter begins with a general mechanistic discussion of metal-hydride-initiated HAT radical reactions. A historical perspective on the origins of the field is then provided, including work by bioinorganic chemists, inorganic chemists, and seminal work by Mukaiyama. Key contributions from the Carreira, Shenvi, and Herzon labs are highlighted.

Utilization of Secondary Interactions to Promote Energy Efficient CO2 Capture and Conversion into Chemical Fuels

Abstract: Burgeoning global energy demand coupled with continually increasing greenhouse gas emissions prompts reassessment of our entire energy infrastructure in order to mitigate climate change and ensure sustainable use for future generations. Capture and conversion of CO2 into chemical fuels can provide a convenient approach to incorporate renewable energy resources into the current energy economy using legacy infrastructure. Current approaches for CO2 capture and reduction remain inefficient however, which results in high costs that prevent their implementation.

Preparation, Conjugation, and Stabilization of Amyloid-β Peptides

Abstract: Aβ peptides are central to the pathogenesis of Alzheimer’s disease. Aβ peptides are highly aggregation-prone, making them challenging to prepare and purify. In the first part of the presentation, I will describe the development of an efficient method for the expression and purification of aggregation-prone amyloid-β (Aβ) peptides, including Aβ(M1-42), 15N-labeled Aβ(M1-42), and Aβ(M1-42) familial mutants.

Filamentous Bacteriophage as a Functional Biomaterial for Biomarker-Based Diagnostics

Abstract: Filamentous bacteriophage have proven to be a powerful biotechnology tool. A direct genotype-to-phenotype relationship makes phage easily genetically modified to display peptide or proteins on their solvent-facing surface. Thus, phage can function as pseudo-antibodies with similar binding affinity and target specificity. Furthermore, rational design of peptide or protein libraries allows for discovery of new target-binders via biopanning.

Investigating the Isolation and Reactivity of Divalent Rare-Earth Metals in Homoleptic and Heteroleptic Environments Containing Cyclopentadienyl Ligands

Abstract: Reduction of tris-cyclopentadienyl rare-earth metal complexes of the form, (C5Me4H)3Ln [Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy], allowed for the isolation of rare-earth metals in the +2 oxidation state. The metal ions in these complexes adopted unusual 4fn5d1 electron configurations with a notable exception for Dy which adopts a 4f10 configuration based on EPR and UV-Vis spectroscopy, and X-ray diffraction. Reaction of these complexes (La, Ce) with tert-butyl isocyanide generated paramagnetic species which feature multi-line EPR spectra at 298 K and 77 K.


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