FIGURE 9.

LC/MS analysis of products formed from TyrOOH-mediated oxidation of CBA. A, MS traces of incubation mixtures containing CBA (0.1 mm) and TyrOOH. Data represent extracted ion chromatograms of species with parent ions with m/z [M + H]⁺ 214.07 and 198.08. B, UPLC traces of mixtures of CBA (0.1 mm) with TyrOOH (0.1 mm) collected using the absorption detector set at 300 nm. Prior to the addition of CBA, the sample of tyrosine (1 mm) was photolyzed in the presence of rose bengal (10 μm), phosphate buffer (50 mm, pH 7.4) over 30 min and, next, preincubated with catalase (100 units/ml) for 5 min. C, profiles of the reactants (i.e. CBA, COH, TyrOOH, and TyrOH, as indicated). Open symbols, reaction profiles when both CBA and TyrOOH were present in the incubation mixtures; solid symbols, reaction profiles upon the absence of CBA or TyrOOH, as indicated.