Figure 5
Kinetic of \({{\rm{O}}}_{2}^{\cdot -}\) decomposition by MnQ2 and MnM2 assayed spectrophotometrically (λ 550 nm) by inhibition of cytochrome c reduction. In the control experiment (black line), xanthine was converted to uric acid in about 150 s (max. absorbance: 0.09; vmax: 0.0021 arbitrary units, AU, s−1). The cytochrome c reduction kinetic changed substantially in the presence of 50 μM MnM2 (red line) (max. absorbance: 0.069; vmax: 0.000457 AU s−1) or 50 μM MnQ2 (purple line) (max absorbance: 0.072; vmax: 0.000460 AU s−1), with a substantially similar catalytic efficiency of MnQ2 and MnM2. ZnM2 (blue line) and ZnQ2 (green line), in which the functional MnII was replaced with redox-inert ZnII, did not induce any significant differences in respect to the control.
