I have spent the last year working in an organic chemistry research laboratory run by Professor Amos Smith. In the Smith Group, my project was to develop peptide staples. Peptide staples are chemical bonds that connect two amino acids in a peptide together to create a peptidic macrocycle. Peptide staples have emerged as a crucial tools for everything from stabilizing peptide drugs to understanding how proteins fold. A variety of staples have already been developed for such purposes, but my project in particular focused on the tetrazine peptide staple.
The tetrazine staple is unique in that it is the first and only staple to date to have ever been unstapled and completely removed from the peptide. It is thus a practical choice for the biophysical analysis of protein folding, and has already been used by the Smith Group to probe the folding of an alpha helix. Additional work on the tetrazine staple in the Smith group optimized the conditions for its incorporation into a wide variety of peptides via two cysteine residues.
However, cysteine is one of the least prevalent amino acids, and not all peptides contain two cysteine residues with which to incorporate the staple. The aim of my project was to develop methods for the incorporation of the tetrazine staple using other amino acids with nucleophilic side chains, namely tyrosine, threonine and serine. I was able to successfully incorporate tetrazine via cysteine and tyrosine residues in a diverse array of peptides. On the other hand, despite many different attempts and approaches, I was unable to incorporate tetrazine via serine and threonine, which both feature an alkyl oxygen nucleophile. In the future, it would be prudent to carry out additional experiments to understand this why incorporation fails.
Throughout the course of this project, I learned many chemical techniques and became much more familiar with the process of scientific research. Through this peptide stapling project, I also had my first involvement in interdisciplinary research, melding together the fields of chemical synthesis and biochemistry. It is my hope that these experiences will serve me well as I begin my graduate school career this fall in the Chemistry Department at Stanford.