L-Selenomethionine is a naturally occurring amino acid containing selenium that is commonly used for the labeling of proteins to facilitate structural determination by x -ray crystallography. Selenomethionine is an antioxidant and has been shown to increase glutathione peroxidase activity in endothelial cells.

CAS Number: 3211-76-5
Formula: C₅H₁₁NO₂Se (molecular weight: 196.11)
Synonyms: (S)-2-amino-4-(methylseleno)butyric acid
Solubility: soluble in water

L-Selenomethionine is supplied in a glass vial containing 250 mg with ≥ 98% minimum purity.