Kinetics and Mechanism of L-Tryptophan Oxidation by Chloramine-T in Basic Medium: A Spectrofluorometric Study

One of the greatest challenges in oxidation research today is the determination of in vivo oxidative stresses. In this investigation, the spectrofluorometry is used to monitor the kinetics of chloramine-T (CAT) oxidation of L-tryptophan (Trp) in basic solutions. The Trp-CAT reaction progress has been monitored at λmax = 485 nm (after using the excitation wavelength of 360 nm) over the temperature range, 293-313 K. The redox reaction follows a first-order dependence of the rate each on [CAT] and [Trp], and an inverse fractional-order on [OH-]. Variations of the ionic strength and the solvent dielectric constant have no effect on the rate. An addition of the reduction product of CAT, p-toluenesulfonamide, to the reaction mixture also has no influence on the rate. Based on the temperature effect, activation parameters are evaluated. A mechanism consistent with the observed kinetic and activation data has been proposed and the rate-law derived.