Figure 3.

Reactivity of TPL-doped gel and TPL in solution with S-Me-Cys. Absorption spectra of TPL-doped gels were recorded in a solution containing 50 mM potassium phosphate (pH 7.5) at 25°C, (A) in the absence (solid line) and presence of 20 mM S-Me-Cys after 30 min of reaction (dashed line) and after subtraction of pyruvate absorbance (dotted line), (B) in the absence (solid line) and presence of 20 mM S-Me-Cys and 5 mM 4-OH-pyr, after 30 min of reaction (dashed line) and after subtraction of pyruvate absorbance (dotted line). Pyruvate concentration was evaluated by a coupled lactate dehydrogenase assay (see Materials and Methods). Insets: Absorbance changes as a function of time at λ = 420 nm (▪), 507 nm (•, A), 504 nm (•, B), and 336 nm (▴). (C) Absorption spectra of soluble TPL in 50 mM potassium phosphate (pH 7.5) at 25°C in the absence (solid line), and presence of 20 mM S-Me-Cys (dashed line) and 20 mM S-Me-Cys and 5 mM 4-OH-pyr (dashed/dotted line). No subtraction for pyruvate absorbance was carried out because spectra were recorded immediately upon mixing.