The role of acid–base equilibria in formal hydrogen transfer reactions: tryptophan radical repair by uric acid as a paradigmatic case

˙) were considered, there would be a large discrepancy with the experimental value (about 4 orders of magnitude), which also supports the finding that the key species in this case are not the most abundant ones. The influence of the pH on the kinetics of the investigated reaction was explored. It was found that the maximum repairing ability of uric acid does not occur at physiological pH, but at a more acidic pH (pH = 5.0).