Optimization of the Glaser-Hay Coupling Reaction to Increase Yield of Bioorthogonal Conjugations (Abstract)

The synthesis of organic products is a complicated process which can involve many steps to reach completion. These products are often used in medical treatments, targeting specific areas throughout the body. For this reason, the product must be both bioorthogonal (able to exist in the cell without disrupting its natural processes) and able to affect only the area(s) in need of treatment. In vitro, researchers often use model compounds to develop medicines that have both of these properties. This summer, I will be using such compounds to find the conditions under which the greatest product yield is produced.

The reaction I will be working with to produce bioorthogonal conjugations is the Glaser-Hay coupling reaction. This reaction utilizes Cu(I) and TMEDA (tetramethylethylenediamine, a bidentate nitrogenous ligand) to catalyze the coupling of two terminal alkynes (Scheme 1).

 

Glaser-Hay Reaction Scheme 2

Scheme 1: The Glaser-Hay coupling reaction occurs between two terminal alkynes with the use of Cu(I) and TMEDA catalysts and a radical scavenger under ambient conditions.

 

For my project, the first alkyne will come from a protein containing an unnatural amino acid (UAA). This product is created through a process involving the transformation of bacterial plasmids, protein expression, and protein purification. The second terminal alkyne is introduced as a functional handle on a fluorophore molecule. The fluorescence of this molecule is used to determine the product yield after the coupling reaction has reached completion. Because this reaction has the potential to produce oxygen radicals, radical scavengers are introduced in order to minimize protein degradation. Each of these factors has the potential to change the yield of the coupling reaction, and so must be tested in combination with each other factor. Further studies investigate the chemoselectivity of this reaction, as well as how a solid-support handle can reduce these issues.

The ultimate goal of my summer research is to find the optimal conditions in which the Glaser-Hay coupling reaction can take place under physiologically relevant conditions. I will be working in Dr. Doug Young’s biochemistry lab on campus, where I have spent the last semester training and learning relevant lab techniques. The timing of this project will allow me to test between 80 and 100 combinations of reaction factors throughout the summer. By testing different combinations of copper sources, ligands, and radical scavengers, I hope to find the combination that produces the highest yield of the desired bioorthagonal conjugation.