L-Methionine is a common sulfur-containing amino acid that is commonly used for the isotopic labeling of methionine protein residues for NMR spectroscopy studies. Methionine is a common methyl-group donor to various substrates, such as creatine, epinephrine, ergosterol, and choline.

EC Number: 200-562-9 (unlabeled)
CAS Number: 49705-26-02
Formula: *CH₃SCH₂CH₂CH(NH₂)COOH (molecular weight: 150.20)
Synonyms: (S)-2-amino-4-(methylmercapto)butyric acid/L-2-amino-4-(methylthio)cutanoic acid

L-Methionine (Methyl-¹³C) is supplied in a glass vial containing 225 mg with ≥99% ¹³C isotopic atom purity.