Phenylthiohydantoin-tyrosine is primarily used in the field of protein sequencing and peptide analysis. It serves as a derivative in the Edman degradation process, a method for determining the amino acid sequence of proteins. By selectively removing one amino acid at a time from the N-terminus of a peptide, it helps in identifying the sequence of amino acids in the protein. This compound is particularly useful in biochemical research and proteomics for studying protein structure and function. Additionally, it aids in the development of therapeutic proteins and the analysis of post-translational modifications, contributing to advancements in medical and biotechnological applications.