N-(5-AMino-1-carboxypentyl)iMinodiacetic Acid Tri-t-butyl Ester 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 produc ts 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.