Fig 2.

Detection of VPO1-mediated Cl-tau by MS. Cl-tau generation and LC-MS were carried out as described in Materials and Methods. Standard Cl-tau (Std) was prepared as follows. First, 20 mM HOCl in 100 mM potassium phosphate buffer (pH 7.4) was added in equal volumes of 100 mM taurine with vigorous stirring. Then, 10 μl of Cl-tau at 80 μM was analyzed. Heme peroxidase-mediated Cl-tau was generated in a 100-μl reaction containing 50 mM potassium phosphate buffer (pH 5.5), 5 mM taurine, 0.8 mM H₂O₂, 100 mM NaCl, and either 1,000 nM/heme VPO1, 100 nM/heme MPO, or 100 nM/heme LPO. The reaction was incubated at 37°C for 30 min. The injection volume for LC-MS was 10 μl. The ion spray voltage was 4,500 V, and nitrogen was the only gas used throughout the runs. The data are representative of at least two independent experiments.