BINDING ABILITY OF CU2-LIKE FRAGMENTS OF BOVINE CASEIN( IONS BY OPIATE)

The coordination modes of Cu(II) to alpha-casein (90-95) and alpha-cas ein (90-96) peptides with opioid activity isolated from pepsin hydroli sates of alpha-casein were investigated by means of electron paramagne tic resonance, absorption, and circular dichroism spectroscopy and pot entiometry. The results allow the identification of the complex specie s involved and the attribution. of the spectral data set to the variou s complex structures. According to the spectroscopic data, a phenolate side-chain of Tyr residue belonging to the Gly-Tyr-Leu or Gly-Tyr-Leu -Gln fragment of the peptides is involved in the metal coordination in a complex which is a minor species at neutral pH range. (C) 1997 Else vier Science Inc.