dialysis of human plasma with histidine

Complexes of transition metals with amino acids in proteins and peptides are uti-lized in numerous biological processes, such as oxygen transport, electron transfer and oxidation. In these processes, the enzymatic active site, which is very specific, often in-cludes several histidine residues, which form complexes with divalent metal ions. Histidine is involved in the coordination of copper ions in several copper proteins, including superoxide dismutase, ceruloplasmin, ascorbate oxidase, etc. In addition, hi-stidine is thought to be involved in the transport of copper into cells in vivo, from albu-min. Copper(II)-histidine complexes have been thoroughly investigated (1–3) and the structure and charge of the complexes have been defined (4–7). A notable review of the copper(II)-histidine complex stability constants and charge can be found (8). According to these concepts, the most probable structure of the complex is Cu(His)2 (Fig. 1)