UC Davis

Metals found in the human body are utilized to maintain normal functions such as cell proliferation, growth, and respiration.1, 2 If trace amounts of metal ions in our body (approximately 10 μM) are not properly maintained, they have been shown to be involved in numerous diseases including cancer and degenerative diseases.3–5 Although we understand that elevated levels of metals may be toxic and have delineating affects to our health, the mechanism behind metals in the body remain unknown due to the lack of tools we currently have to be able to selectively trace these metals in the extracellular space.This thesis describes the strategies and challenges towards developing probes that are selective for metals in the extracellular space. Thus far, a peptide library was first built to discover potential Cu(II)-binding peptides. This peptide was then synthesized and conjugated to a fluorophore. Lastly, the Cu(II)- binding peptide was purified and subjected to cell-based assays to validate the utility of the peptide as a probe. Unnatural amino acids have been shown to be more stable and targeted for metal binding when utilized for drug delivery or probes.6 To further develop a potential Cu(II) selective probe, bipyridine-alanine unnatural amino acid was a good candidate to include for a future peptide library. Synthesis optimization for this unnatural amino acid are also discussed in this thesis. Taking inspiration from my previous project for developing a Cu(II)-selective probe, oxytocin, a peptide hormone, has been studied to rely on metals in order to be recognized by the oxytocin receptor.7 Since oxytocin is a cyclic peptide, reduced oxytocin (linear) analogs were designed and synthesized in hopes to be studied for Zn(II) mediated binding in order for oxytocin receptor recognition. With fluorophore conjugation, it could then be investigated as a probe for Zn(II). Altogether, the outcome of my thesis is to describe the approaches used thus far to develop peptide probes for monitoring copper and zinc in the extracellular space.