The interplay between sequence, structure and function is an underlying theme in biological systems. Proteins, in particular, have evolved the ability to access a virtually infinite set of three-dimensional architectures from a small collection of building blocks; it is precisely this complexity of form that finely tunes their functional specificity. β-Peptides are a class of unnatural polyamides known to adopt structural motifs that are in many ways reminiscent of protein folds in nature. This dissertation first investigates the relationship between sequence and structure in self-assembling β-peptides, then demonstrates how the latter translates into function.
Chapter 1 provides an overview of the fundamental principles guiding β-peptide helix formation and self-assembly, and describes their applications both within and outside of the biological context. The ability of β-peptides to mimic natural α-helices while maintaining proteolytic resistance allows them to serve as therapeutic agents by targeting, for example, protein-protein interactions. Their unique stability in both aqueous and organic environments further enables the development of β-peptide-based nanomaterials and organocatalysts.
Chapter 2 elucidates the relationship between β-peptide primary sequence and quaternary structure based on the biophysical characterization of the Acid-3Y bundle. Acid-3Y was designed by substituting isoleucine for leucine side-chains in the sequence of the previously characterized octamer, Acid-1Y. The finding that Acid-3Y assembles into a tetrameric bundle suggests that branching at the γ-carbon of hydrophobic residues plays a critical role in determining β-peptide bundle stoichiometry.
Chapter 3 explores the potential of β-peptide bundles to mimic enzyme structure and function. The demonstration of β-peptide mutarotase activity in benzene highlights the importance of macromolecular preorganization in catalysis, while the ability of rationally designed β-peptide bundles to catalyze ester hydrolysis in water represents a crucial step towards the functionalization of these unnatural macromolecules. The dependence of catalytic activity on both active site geometry and bundle assembly, together with their substrate selectivity, underscores the unique biomimetic capacity of β-peptides.
Chapter 4 describes the rational design of a β-peptide ligand for the parathyroid hormone 1 receptor (PTH1R). Using previous strategies that led to the identification of p53 and GLP-1 mimics, a 12-member β-peptide library was constructed and tested in vitro for binding to the receptor protein. Although no hits were found from this initial screen, subsequently designed α/β-peptide chimeras showed promise as synthetic antagonists of PTH1R with improved pharmacokinetic properties.
Chapter 5 summarizes the key results of this dissertation and offers a perspective on possible future research directions. A breakthrough in the field of β-peptides would rely on the development of a method to synthesize genuine "β-proteins" with more sophisticated structure and function.
|School Location:||United States -- Connecticut|
|Source:||DAI-B 75/09(E), Dissertation Abstracts International|
|Keywords:||Artificial enzyme, Catalysis, Foldamers, Peptides, Self-assembly|
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