2-amino-5-[(N'-propylcarbamimidoyl)amino]pentanoic acid 2-amino-5-[(amino-propyliminomethyl)amino]pentanoic acid 2-amino-5-[(N'-propylcarbamimidoyl)amino]valeric acid HSCI1_000246 N-PLA NG-Propyl-L-arginine Nomega-Propyl-L-arginine