Figure 4

Average pKa determination of ChTg. rChTg (0.6 µM) was reacted with CDNB (1 mM) at variable pH values (purple line). Average pKa = 8.1 ± 0.1 of the ten reactive cysteines in rChTg. As a control experiment GSH (100 µM) was reacted with CDNB (1 mM) at variable pH values (gray line). The error bars represent the S.D. from three independent experiments. The theoretical curve (black line) of an unperturbed protein cysteine (pKa = 9.1) is also reported.