Phenylthiohydantoin-glutamic acid is primarily used in biochemical research, particularly in the field of protein sequencing. It serves as a derivative in the Edman degradation process, a method for stepwise removal and identification of amino acids from the N-terminus of a polypeptide chain. This compound helps in the precise analysis of protein structures by enabling the identification of glutamic acid residues during sequencing. Additionally, it finds application in the study of peptide synthesis and modification, aiding researchers in understanding protein function and interactions. Its role in analytical biochemistry is crucial for advancements in proteomics and molecular biology.