POTENTIOMETRIC AND SPECTROSCOPIC STUDY OF THE COMPLEXATION OF COPPER(II) IONS BY TRIPEPTIDES CONTAINING AROMATIC SIDE-CHAINS

The complexation of copper(II) ions with L,L-Gly-Phe-Phe, L,L-Phe-Gly- Phe and L,L-Phe-Phe-Gly was studied by potentiometric and spectroscopi c measurements. Only four complexes have been found for each copper(II )-tripeptide system, and no species with two ligand molecules was obse rved. The results show influences of aromatic sidechains. These influe nces are dependent upon the location of two aromatic rings in studied tripetides. The stabilization or destabilization of a given complex is probably the result of several different effects, including steric hi ndrance, hydrophobic effect, electrodonor effect and pi-d interaction. The spectroscopic measurements, e.s.r and electronic absorption, are useful to determine the complex structures.