Figure 3.

Kinetic and mechanism studies of chlorooxime-thiol conjugations. a) Real-time monitor of conjugate reaction using UV-Visible absorbance at 247 nm (max absorbance wavelength for chlorooxime FC1). Reaction conditions: GSH (50 μM), chlorooxime (50 μM) in PBS pH 7.4 at room temperature. b) Plotting the natural logarithm of the concentration of FC1 (M) versus time (s) for the reactions of FC1 (50 μM) with BME (50 μM), GSH (50 μM), GSH (100 μM), GSH (250 μM), respectively. c) Plotting observed first-order rate constant k₁ versus the initial concentration of GSH. Based on the observation k₁ = k_{2, app.}×[GSH]₀, the slope of the curve gives the overall rate constant k_{2, app.} of 306 ± 4 M⁻¹s⁻¹. d) Proposed mechanisms for cysteine-chlorooxime conjugation.