Synonyms: [2,4'-Bi-1H-indole]-3,3'-dipropanoicacid, a,a'-diamino-6',7'-dihydro-6',7'-dioxo-, (aS,a'S)- (9CI); [2,4'-Bi-1H-indole]-3,3'-dipropanoic acid,a,a'-diamino-6',7'-dihydro-6',7'-dioxo-, [S-(R*,R*)]-;TTQ; Tryptophan tryptophylquinone; Tryptophanyltryptophan quinone