Fig 6. Reactivity between Cys34 and DTNB.

(A) Scheme of the reaction between DTNB and a thiol. (B) DTNB (0.2 mM) was mixed with reduced DomI (11.5 μM, black solid trace) or reduced HSA (10 μM, blue dash-dotted trace) in phosphate buffer (20 mM, pH 7.4), and absorbance at 412 nm was recorded at 25°C. Exponential plus straight line equations (Abs = amplitude (1 –exp (-k_obst) + slope t + offset)) were fitted to the data to determine the amplitude and k_obs. Controls with DTNB alone (red dotted trace) or DomI alone (green dashed trace) were also performed. (C) Secondary plot for the reaction of DTNB and DomI (11.5 μM, black circles) or HSA (20 μM, open circles). For both proteins, the second order rate constants of the reaction with DTNB were obtained from the slope of the linear fit.