The molecule is an L-alpha-amino acid zwitterion formed from S-(5-histidyl)cysteine sulfoxide by transfer of protons from the two carboxy to the two amino grousp; major species at pH 7.3. It derives from a L-histidine zwitterion and a L-cysteine zwitterion. It is a tautomer of a S-(5-histidyl)cysteine sulfoxide.
(2S)-2-azaniumyl-3-[4-[(2R)-2-azaniumyl-2-carboxylatoethyl]sulfinyl-1H-imidazol-5-yl]propanoate