Abstract: Glaser-Hay Bioconjugations with Unnatural Amino Acids

Hello everyone!

My name is Megha Vipani and I am a rising junior majoring in Chemistry.  I have been a member of Dr. Douglas Young’s biochemistry lab since the beginning of my sophomore year and I’m excited to continue my work over the summer! I will be focusing on the incorporation of unnatural amino acids into green fluorescent protein for bioconjugation via Glaser-Hay reactions.

Bioconjugation is the linking of two biologically relevant molecules that could include probes, fluorophores, or antibodies. Our lab is interested in developing methods for bioconjugation as it allows for the targeting of specific proteins within cells.  One effective method involves the use of unnatural amino acids (UAA) as specific attachment sites for bioconjugates. Over the past few months, I have been working to synthesize a derivative of the amino acid tyrosine with an alkyne functional group. The alkyne group adds a unique functionality that is not present in any of the 20 naturally occurring amino acids and affords new reactivity to a protein. The alkyne tyrosine (Figure 1) will be incorporated into green fluorescent protein (GFP), a commonly used model protein, to study bioconjugation using the alkyne functionality.

Alkyne Tyrosine

Figure 1. Alkyne Tyrosine

Once the UAA has been successfully incorporated into GFP, a variety of molecules such as fluorophores, antibodies and toxins could be targeted to this protein in a site-specific manner.  I will be utilizing the Glaser-Hay reaction to link fluorophores to the alkyne tyrosine. Glaser-Hay reactions allow the coupling of two terminal alkynes to form a polyyne using a copper catalyst. The use of a fluorophores will allow the determination of successful bioconjugation. I will also compare the fluorescence of wild-type GFP with GFP with the UAA to study the effect of the UAA on GFP function.

The goal of my research is to develop bioconjugation as a potential method of targeted drug delivery and imaging. If the Glaser-Hay reaction is optimized to biological conditions, molecules known to have therapeutic effects on certain cells could be attached to an alkyne group and targeted towards a specific protein within the cell.

Thanks for reading and I look forward to sharing updates about my work!