Copper(II) complexes with some tetrapeptides containing the ‘break-point’ prolyl residue in the third position

Abstract

The tetrapeptides Phe-Gly-Pro-Phe, Phe-Gly-Pro-Tyr, and Tyr-Gly-Pro-Phe have been synthesised and their complexes with H⁺ and Cu²⁺ studied by potentiometry and spectroscopy (u.v., visible, c.d., and e.s.r.) at 25 °C and l= 0.10 mol dm^–3(KNO₃). The results show that with both tetrapeptides containing the Tyr residue, TyrO^––Cu bonding is present at pH > 8. With Tyr-Gly-Pro-Phe this is achieved through the formation of dimeric complexes while with Phe-Gly-Pro-Tyr a monomeric complex with a large chelate ring is formed.