Low molecular weight copper-binding ligands in human bile.

The aim of this study was to detect and identify major low molecular weight (less than 10,000) copper-binding ligands in human bile. Modified gel chromatography was used as the method of ligand detection because it ensures the detection of labile as well as inert metal-ligand complexes. Conjugated bilirubin, peptides, and amino acids, primarily glycine, were isolated as the major ligands. In contrast to the other copper-binding ligands, the peptides were poor zinc binders, suggesting the possibility that they may confer necessary specificity to trace metal elimination.