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. Author manuscript; available in PMC: 2012 Aug 6.
Published in final edited form as: Chem Res Toxicol. 2011 Nov 22;24(12):2217–2226. doi: 10.1021/tx2003323

Figure 5.

Figure 5

Preincubation experiment with cysteine and horseradish peroxidase/H2O2. 10 mM cysteine were preincubated (15 min, room temperature) with 50 mM one DMPO isotope. Then, 50 mM the other DMPO isotope, 1 mg/ml HRP and 10 μM H2O2 were added and the ESR spectrum was recorded. A: Preincubation with 14N-DMPO, incubation, addition of 15N-DMPO, enzyme and H2O2. B: Preincubation with 15N-DMPO, thereafter addition of 14N-DMPO, HRP and H2O2. Both signals are almost identical and the residual (C; A minus B) consists of noise. This demonstrates that no significant Forrester-Hepburn artifact contributed to the spectrum.