Phenylthiohydantoin-aspartic acid is primarily utilized in the field of biochemistry and molecular biology for protein sequencing and amino acid analysis. It plays a crucial role in the Edman degradation process, where it helps in the step-wise identification of amino acids in a peptide chain. By selectively cleaving the N-terminal amino acid and converting it into a phenylthiohydantoin derivative, this compound aids in determining the sequence of proteins with high precision. Additionally, it is employed in research laboratories to study protein structure and function, contributing to advancements in understanding diseases and developing therapeutic interventions. Its application is also seen in the synthesis of peptides and in quality control processes for protein-based pharmaceuticals.