Solvent effects on the oxidation of TyrOH by SO4•- radical

This work presents the study on the oxidation of TyrOH by SO4.- in water/ACN mixed media. Investigations show that the reaction mechanism between TyrOH and SO4.- does not change by the addition of ACN, whereas the kinetic behavior of the transient species produced is significantly affected. The decay of SO4.- decelerates with increasing volume fraction of ACN in mixed media whereas the decay of TyrO(.) accelerates. We suggest that the contrary effects of the solvent on the decay of both SO4.- and TyrO(.) are due to their different charges. The deceleration of the oxidation of TyrOH by SO4.- with the increase of ACN fraction may demonstrate that in the presence of organic solvents the redox potential of TyrO(.)/ TyrOH is altered, which provides support for the suggestion that the redox potential of TyrO(.)/TyrOH might be altered with their inclusion into peptides and proteins.