Vol. 6, Issue 11 (2017)

Author(s):
Yogeshwar Sharma

Abstract:
The kinetics of the complexation of Cu(II) with γ-L-glutamyl-L-cyteinylglycine (IUPAC name: (2S)-2-Amino-4-{[(1R)-1-[(carboxymethyl)carbamoyl]-2-sulfanylethyl]carbamoyl}butanoic acid) has been investigated at 25, 30, 35 and 40± 0.05 °C in the pH range 2.51-3.53 using Aminco Morrow Stopped Flow Spectrophotometer. The ionic strength was maintained at 0.1 M KNO3. No indicator was used for this complexation reaction because transmittance changes were large enough to be monitored directly. The anionic form of γ-L-glutamyl-L-cyteinylglycine is more reactive and the protonated form interacts only to a small extent. Kinetic results indicate that the ligand is not involved in the rate determining step which is, in fact, associated with the release of a water molecule from the shell of the metal ions prior to complexation with the ligand. Enthalpy, entropy of activation, energy of the molecule and heat of formation were also calculated. A mechanism consistent with the kinetic data has been suggested.