Study of Zinc-glycylglycine Complex with Ninhydrin in Aqueous and Cationic Micellar Media: A Spectrophotometric Technique

Abstract

Abstract Studies of the interaction between the zinc-peptide complex ([Zn(II)-Gly-Gly]+) and ninhydrin in aqueous and CTAB surfactant media were executed by the means of UV-visible spectrophotometry. The reaction rates (k obs and k ψ) were determined in both media by varying different parameters such as pH, temperature and the concentration of the reactants and CTAB. The micellar binding constants and activation parameters were also calculated. The catalytic activity in the CTAB medium was found to be better than in the aqueous medium on the title reaction. The catalysis by CTAB is treated quantitatively by applying the model of the kinetic pseudo-phase of the micelle. Variation of the rate constant with the change of the CTAB concentration was used for the calculation of several kinetic parameters such as the binding constants (K B and K Nin) and the micellar rate constant k m. On basis of the experimental results, a probable mechanism is proposed.