Date of Award

5-2023

Document Type

Honors Thesis

Degree Name

Bachelor of Science

Department

Biological Science

Advisor/Committee Chair

Qiang Zhang

Major

Biology

Committee Member

Andrew Berglund

Abstract

Polypeptides and proteins play crucial roles in biological systems, including enzymatic activity regulation, molecule transport, and cell and tissue structural support. Amino acids are the building blocks of peptides and proteins, and peptides can act as hormones, neurotransmitters, and enzymes. Proteins are made up of one or more polypeptide chains and have diverse functions such as catalyzing chemical reactions, transporting molecules, and providing structural support. Protein preparation can be done biologically by expression systems or isolation and purification from natural sources. While these methods have their advantages, they also have their shortcomings. Chemical synthesis is an alternative method that allows for the introduction of post-translational modifications and non-canonical amino acids with precise control over their location and frequency. Solid-phase peptide synthesis (SPPS) is a widely used chemical synthesis method that involves the use of a solid support, typically a resin, to which the first amino acid of the peptide is attached. Subsequent amino acids are then added one at a time, in a stepwise fashion, with each amino acid protected by a temporary functional group that prevents unwanted side reactions. The use of a solid support allows for easy purification of the desired peptide and allows for the synthesis of longer and more complex peptides. Chemical synthesis methods have advantages such as precise control over PTMs, introducing non-canonical amino acids, and the ability to produce proteins that are difficult to obtain through biological methods. In this thesis, we propose two primary methods of peptide synthesis; 1.) intermolecular bonding of disulfide bond using and 2.) synthesis of protecting group-free sugar-containing oligopeptides. The study aims to synthesize a disulfide-rich peptide using solid-phase peptide synthesis and reacting it with a phosphate buffer to investigate the formation of mixed disulfide bonds. The experiments involve various analytical techniques, such as HPLC and mass spectrometry. Overall, these studies enriched our understanding of thiol functional group reactivities in the polypeptide settings and complemented the existing thiol oxidation tactics.

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