Macrocyclic β-Hairpin Peptides Derived from Amyloid β, Medin, and the IQGAP1 WW Domain And Conversion of In-Person Chemistry Courses to Online Versions in Response to the COVID-19 Pandemic
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Macrocyclic β-Hairpin Peptides Derived from Amyloid β, Medin, and the IQGAP1 WW Domain And Conversion of In-Person Chemistry Courses to Online Versions in Response to the COVID-19 Pandemic

  • Author(s): Howitz, William James
  • Advisor(s): Nowick, James S
  • et al.
Abstract

The dissertation is composed of two sections. The first section is composed of chapters one, two, and three and describes the study of macrocyclic β-hairpin peptides derived from β-sheet peptides. The second section is composed of chapters four and five and discusses the curricular innovations made to support the remote instruction of an organic chemistry lecture course, a general chemistry laboratory course, and an organic chemistry laboratory course at the onset of the COVID-19 pandemic. Chapter 1 describes the use of acetylation as a means to modulate and study the effect of charge on the oligomeric assembly and toxicity of familial Alzheimer’s disease (FAD) mutants of Aβ. FAD is an inherited form of Alzheimer’s disease that has an earlier onset due to point mutations within the sequence of Aβ that alter the rate of aggregation and toxicity of the peptide. The most common site of these mutations is position 22 in which the native glutamic acid may be replaced with a glycine (E22G), glutamine (E22Q), or lysine (E22K). Previous work in our lab using a macrocyclic chemical model system of the Aβ peptide that incorporates residues 16-22 and 30-36 established that there was a correlation between the net charges of these mutant peptides and their oligomeric assemblies and toxicities as measured by SDS-PAGE, LDH-release assays, and dye leakage assays. In this chapter I further probe the effect of charge on the oligomeric assembly and toxicity of the FAD mutant peptides using our lab’s chemical model system of Aβ. To control for the hydrophobicity and size of the residues that vary between the mutants, I used acetylation as a tool to manipulate the net charge of the peptides. This work demonstrates that the toxicities of the peptides strongly correlate with their net charges based on LDH-release assays and dye leakage assays. The oligomeric assemblies of the peptides assessed by SDS-PAGE suggest that charge is a factor that impacts their assembly, but that the position of acetylation also influences the assembly. Chapter 2 discusses the synthesis and X-ray crystallographic structure of a macrocyclic peptide derived from an amyloidogenic peptide called medin. Amyloidogenic peptides and proteins are rich sources of supramolecular assemblies. Sequences derived from well-known amyloids, including Aβ, human islet amyloid polypeptide, and tau have been found to assemble as fibrils, nanosheets, ribbons, and nanotubes. The supramolecular assembly of medin, a 50-amino acid peptide that forms fibrillary deposits in aging human vasculature, has not been heavily investigated. In this chapter, I present an X-ray crystallographic structure of a cyclic β-sheet peptide derived from the 19−36 region of medin that assembles to form interpenetrating cubes. The edge of each cube is composed of a single peptide, and each vertex is occupied by a divalent metal ion. This structure may be considered a metal−organic framework (MOF) containing a large peptide ligand. This work demonstrates that peptides containing Glu or Asp that are preorganized to adopt β-hairpin structures can serve as ligands and assemble with metal ions to form MOFs. Chapter 3 presents the development of an IQGAP1 WW domain-derived peptide with the ability to bind p110α. IQGAP1 is a scaffold protein that mediates the PI(3)K-Akt pathway that is upregulated in many cancers. The WW domain within the scaffold directly binds to p110α, one of the subunits of PI(3)K. Disrupting the interaction between p110α and the WW domain using a competitive inhibitor has been proposed as a promising approach to selectively negatively affecting cancer cells dependent on the PI(3)K-Akt pathway. In this chapter, I share the design and synthesis of a β-hairpin mimic peptide derived from the WW domain of IQGAP1, and I demonstrate that the peptide can compete for binding to p110α against the native IQGAP1 WW domain. This study is ongoing and future work will focus on elucidating the secondary structure of the peptide inhibitor by NMR and X-ray crystallography and determining if the secondary structure the peptide adopts is essential for its binding capability. Chapters 4 and 5 describe the conversion of in-person chemistry courses to online versions in response to the COVID-19 pandemic. As the SARS-CoV-2 pandemic spread throughout the world, universities were faced with extraordinary challenges. Shelter-in-place orders were given, in-person classes were cancelled, and at the University of California Irvine, instructors had less than two weeks to convert spring quarter classes from a face-to-face to an online format. A team-based approach was essential to making this transition. In chapter 4 I share the insights gained during the design and implementation of the final quarter of a large-enrollment online organic chemistry course, as well as student perspectives on the efficacy of key components of the course. In chapter 5, I describe how the curricular, administrative, and logistical challenges of high enrollment general and organic chemistry laboratories were addressed in the transition to remote teaching. I discuss the reasoning behind the approach, how the existing web-based course content was leveraged, the additions and alterations to the curriculum, the replacement of experimental work with videos, the results of both student and TA surveys, and the lessons learned for iterations of these courses in the near future.

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