2-Amino-8-oxononanoic acid (hydrochloride) is the hydrochloride form of 2-Amino-8-oxononanoic acid. 2-Amino-8-oxononanoic acid is an amino acid, incorporation into proteins in E.coli in genetic. 2-Amino-8-oxononanoic acid is efficient in labeling of proteins with different probes with a site-specific manner under a mild condition close to the physiological pH.