(2S)-2-amino-5-[(N'-propylcarbamimidoyl)amino]pentanoic acid (2S)-2-amino-5-[(amino-propyliminomethyl)amino]pentanoic acid (2S)-2-amino-5-[(N'-propylcarbamimidoyl)amino]valeric acid NCGC00025034-01 Tocris-1200 3AR