Mn(II)-sodium dodecyl sulphate complex mimic enzyme-catalyzed fluorescence quenching of Pyronine B by hydrogen peroxide

Mn(II)-sodium dodecyl sulphate complex (Mn(II)-SDS) is used to mimic the active group of peroxidase. The catalytic characteristic of this mimic enzyme catalyst in the oxidation reaction of fluorescence substrate, tetraethyldiaminoxanthyl chloride (Pyronine B (PB)), with hydrogen peroxide has been studied. The experimental results show that Mn(II)-SDS complex has similar catalytic activity that of peroxidase. The steady-state catalytic rate depends upon mimic enzyme and substrate concentrations, and the Michaelis-Menten parameters K_m, V_max and K_cat are 7.6×10⁻⁶ M, 7.9×10⁻⁷ M s⁻¹ and 7.9 s⁻¹, respectively. The catalytic activity of Mn(II)-SDS complex is compared with those of HRP and Hemin. Though the catalytic activity of Mn(II)-SDS complex is 15.9% of that of HRP, it can catalyze the oxidation reaction of PB with hydrogen peroxide lead to fluorescence quenching of PB. Under optimum conditions, linear relationship between fluorescence quenching F₀/F and concentration of H₂O₂ is in the range of (0.0-3.6) × 10⁻⁷ M. The detection limit is determined to be 3.0×10⁻⁹ M. By coupling this mimic catalytic reaction with the catalytic reaction of glucose oxidase (GOD), glucose can be detected. Linear relationship between F₀/F and concentration of glucose is in the range of (0.0-1.4) × 10⁻⁷ M. The detection limit is determined to be 4.2×10⁻⁹ M. This method is applied to the determination of glucose in human serum and the results are in good agreement with the phenol-4-aminoantipyrine (4-AAP).