A series of tripodal ligands L derivedfrom nitrilotriacetic acid (NTA) and extended by three converging metal-binding cysteine chains were previously found to bind selectively copper(I) both in vitro and in vivo. The ligands L1 (ester) and L2 (amide) were demonstrated to form copper(I) species with very high affinities, close to that reported for the metal-sequestering metallothioneins (MTs; log KCu-MT