Phenylthiohydantoin-glycine is primarily utilized in the field of biochemistry and molecular biology for protein sequencing and peptide analysis. It serves as a derivative in the Edman degradation process, a method used to determine the amino acid sequence in proteins. By reacting with the N-terminal amino acid of a peptide, it forms a stable compound that can be easily identified, allowing researchers to sequentially analyze and identify the amino acids in a protein. This application is crucial for understanding protein structure and function, which has implications in drug development, genetic research, and the study of diseases. Additionally, it aids in the synthesis and modification of peptides for various biochemical studies.