PhD defenses.

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.

New tools and technologies based on nature’s light-emitting chemistry

Abstract: Bioluminescent enzymes (luciferases) are among the most popular reporters for illuminating biological processes in vivo. Luciferases emit light by catalyzing the oxidation of small molecule luciferins. Since no excitation light is needed, there is virtually no background signal. Thus, bioluminescence imaging (BLI) is extremely sensitive and well-suited for applications in tissues and whole organisms.

Fundamental Investigations of Metal-Metal Oxide Model Catalysts and the Liquid/Vapor Interface of Aqueous Solutions

Abstract: Fundamental surface science investigations are primarily concerned with understanding the chemistry that occurs at the interface of phases, such as the solid/gas, solid/liquid, and liquid/vapor interface. Surface science investigations have led to breakthroughs in understanding chemisorption and physisorption on heterogeneous catalysts, reactions that occur at the interface of electrodes, and hydrogen bonding in aqueous solutions.

Developing new imaging tools inspired by nature's flashlight

Abstract: Bioluminescence imaging with luciferase-luciferin pairs is routinely used to monitor cellular events in real time. This technology relies on enzymes (luciferases) that catalyze the adenylation and oxidation of small molecules (luciferins), resulting in light. While powerful, this imaging modality has rarely been applied to multicomponent imaging due to a lack of distinguishable probes. Recent efforts have expanded the bioluminescence toolkit by engineering luciferases that selectively react with synthetic substrates (i.e., “orthogonal pairs”).

Secondary Coordination Sphere Effects on Properties and Reactivities of Metal complexes

Abstract: In nature, metalloproteins can perform difficult transformations with high selectivity and efficiency through precise control of the primary and secondary coordination sphere. Synthetic chemists have developed biomimetic ligand scaffolds to better understand the coordination environments in the active sites of metalloproteins. However, besides the ligands covalently bound to the metal center, control of the secondary coordination sphere that is comprised of non-covalent interactions also has significant influence in complex properties.

Understanding the Mechanisms of Salt Formation in New Particle Formation and Growth Using Nanoparticle Composition Measurements and Computational Modeling

Abstract: Atmospheric nanoparticle formation and growth processes are major sources of uncertainty in our understanding of global climate. However, nanoparticle composition is notoriously difficult to measure below 30~nm due to their incredibly low mass, and so a full understanding of the compounds that contribute to nanoparticle growth still remains elusive. In addition, nanoparticle physical and chemical properties are continuously changing at different sizes.

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