Methionine is one of two amino acids containing sulfur (cysteine is the other). The sulfur-containing amino acids cysteine and methionine are generally considered to be nonpolar and hydrophobic. Methionine is so hydrophobic it is almost always found on the interior of proteins.
Methionine as the free amino acid plays several important roles in metabolism. It can react to form S-Adenosyl-L-Methionine (SAM) which servers at a methyl donor in reactions.
The chemical linkage of the sulfur in methionine is a thiol ether.
Unlike cysteine, the sulfur of methionine is not highly nucleophilic, although it will react with some electrophilic centers. It is generally not a participant in the covalent chemistry that occurs in the active centers of enzymes.
Texas Transdermal’s Amino Acid patch contains the proper dose of Methionine.
Source: Department of Biochemistry and Molecular Biophysics – University of Arizona