FIG. 3.

a: The EPR spectra of 100 μM RSSR measured at various time points after incubation with 2.5 mM GSH in 0.1 M Na-phosphate buffer, pH 7.2, and 1 mM DTPA at 34°C. b: The kinetics of the increase of amplitude of low-field monoradical component of the EPR spectrum after addition of various concentrations of GSH: 0.625 mM (△), 1.25 mM (○) and 2.5 mM (□). Lines represent the best fit of the experimental kinetics to the monoexponents. Inserts: The dependence of inverse time constant of the exponential kinetics, 1/τ, on GSH concentration. The linear regression (1/τ = k_obs × [GSH]) provides the observed rate constant value of the reaction between GSH and RSSR, k_obs (pH 7.2, 34°C) = 2.8 ± 0.2 M⁻¹ s⁻¹.