(5S)-N-(5-AMINO-1-CARBOXYPENTYL)IMINODIACETIC ACID HYDRATE is a nitrilotriacetic acid derivative used as a metal chelating adsorbent for metal ion affinity chromatography. This method can be used for identification and rapid one-step purification of gene products expressed as fusion proteins with an oligo-histidine tag. The oligo-histidine tag serves as a high affinity binding sequence for the purification of fusion proteins via a metal chelating absorbent such as N-(5-Amino-1-carboxypentyl)iminodiacetic acid. Also soluble in DMSO:DMF 1:1 and DMSO:CH2Cl2 1:2