Coordination abilities of tetrapeptides containing proline and tyrosine—A spectrophotometric and potentiometric study

Abstract

The synthesis of three tetrapeptides, Gly-Pro-Gly-Tyr. Gly-Pro-Tyr-Gly. and Tyr-Pro-Gly-Gly, are described. All contain proline as the second amino acid subunit to act as a break point in metal complex formation. The proton and copper(II) complex formation constants have been measured at 22°C and l = 0.10 mol dm −3 (KNO 3). The copper(II) complexes have also been studied spectrophotometrically over the pH range of 6–11 by absorption spectroscopy (800–200 nm), circular dichroism spectroscopy, and electron paramagnetic resonance spectroscopy. The experimental data have been combined to determine the complex species present as a function of pH and the coordination centers used.