The molecule is a quaternary ammonium ion consisting of L-histidine with a 3-(trimethylammonio)-3-carboxypropyl group at the 2-position of the the imidazole ring. It is a conjugate acid of a diphthinate.
[(1S)-3-[5-[(2S)-2-amino-2-carboxyethyl]-1H-imidazol-2-yl]-1-carboxypropyl]-trimethylazanium