An amino acid with this element is coded for by the UGA codon, which is normally a stop codon.
Thressa Stadtman is particularly known for studying the biochemistry of this element. This element's dioxide is used for the oxidation of alkenes to allylic alcohols and ketones to alpha-diketones. This element is found in the active site of an enzyme subfamily that catalyzes the removal of an iodine from T4 to form T3, which is active, or reverse T3 or T2, which are inactive; that enzyme subfamily is the iodothyronine deiodinases. Glutathione peroxidases and thioredoxin reductases contain this element at their active site. An amino acid with this element is coded for by the UGA codon, which is normally a stop codon. That amino acid is an analog of cysteine with this element in place of sulfur. For 10 points, identify this chalcogen that is just heavier than sulfur.
Thressa Stadtman is particularly known for studying the biochemistry of this element.
selenium [or Se]