Phenylthiohydantoin-alanine is primarily used in the field of protein sequencing and peptide analysis. It plays a crucial role in the Edman degradation process, a method for determining the amino acid sequence in proteins. By selectively cleaving and identifying amino acids one at a time from the N-terminus of a peptide, it helps researchers accurately map out protein structures. This is essential for understanding protein function, studying genetic mutations, and developing targeted therapies in biomedical research. Additionally, it is utilized in analytical chemistry to validate the purity and composition of synthetic peptides. Its application is vital in advancing proteomics and biochemistry studies.