Year of Publication

2007

Document Type

Dissertation

College

Arts and Sciences

Department

Chemistry

First Advisor

Arthur Cammers

Abstract

Peptides are short, sequence and length specific oligomers composed of small amino acid residues. Nature has refined these peptide sequences and their endogenous function through evolution. In addition, peptides have played an important role in medicine, which has lead to further research into developing peptides as lead pharmaceuticals (therapeutic peptides). Unfortunately, therapeutic peptides are inferior as drug candidates due to their low oral bioavailability; immunogenicity and potential to be attacked by peptidases. Fortunately, peptides can be modified by steric constraints, cyclization, and/or replacement of the peptide backbone itself creating a mimic (peptidomimetic) of the original peptide. Peptidomimetics are deliberately designed to have increased protease resistance, reduced immunogenicity and improved bioavailability when compared to the original endogenous peptide. One such peptide, Magainin is a O One such peptide, Magainin is a well-studied, a-helical peptide found in African clawed frogs. This peptide has antibiotic properties (against pathogenic bacteria), which partly arises from the hydrophilic portion of the peptide having basic amino acid side chains periodically disposed on one side of the a-helix. This property of magainin causes its attraction to negatively charged bacteria cell membranes. Unfortunately, as in the case of other antibiotics, pathogenic bacteria have developed effective countermeasures against magainin. We designed a peptidomimetic based on magainin and implemented a plan to determine what type of molecules could be assembled for a magainin mimic. We successfully utilized molecular modeling (Monte Carlo conformational search), as well as results from previous experiments to elucidate what type of molecules, as well as how many molecules would be necessary to create a novel helical-like magainin peptidomimetic. It was discovered that C2 symmetric diamines would be best at generating the helical-like motif and the amino acid lysine to generate the basic side chain. The next step was the successful connection of two C2 symmetric molecules via a urea linkage and then one more connection to a lysine (a-amino group) residue, creating a short sequence of oligoureas (trimers). Finally, attempts to connect the oligoureas trimers were attempted using a solid-phase synthesis approach to generate a functional magainin mimic.

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