Phenylthiohydantoin-valine is primarily used in the field of protein sequencing and peptide analysis. It plays a critical role in the Edman degradation process, a method for determining the amino acid sequence of proteins. Specifically, it is formed as a derivative during the cleavage step of the Edman degradation, allowing researchers to identify the N-terminal amino acid of a peptide or protein. This compound is essential for analyzing protein structures, understanding their functions, and studying post-translational modifications. Its application is particularly valuable in biochemistry, molecular biology, and proteomics research, aiding in the development of diagnostic tools and therapeutic agents.