The molecule is a 2-(3-amino-3-carboxypropyl)-L-histidine in which position 3 on the side-chain has S-configuration. It is a tautomer of a 2-[(3S)-3-amino-3-carboxypropyl]-L-histidine dizwitterion.
(2S)-2-amino-4-[5-[(2S)-2-amino-2-carboxyethyl]-1H-imidazol-2-yl]butanoic acid