Fmoc-L-Selenomethionine is primarily used in peptide synthesis, particularly in solid-phase peptide synthesis (SPPS). It serves as a protected form of selenomethionine, allowing for the incorporation of selenium into peptides. This is especially valuable in the study of selenoproteins and their functions, as selenium plays a critical role in enzymatic activity and antioxidant defense. The Fmoc group provides temporary protection during synthesis, ensuring selective deprotection and accurate peptide chain assembly. Additionally, it is utilized in structural biology for X-ray crystallography, where selenium acts as an anomalous scatterer to aid in phase determination and protein structure elucidation. Its application extends to biochemical research, enabling the exploration of selenium's role in redox regulation and cellular signaling pathways.