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. 2018 Jan 10;28(2):131–140. doi: 10.1089/ars.2017.7106

FIG. 1.

FIG. 1.

Spin-trapping EPR spectroscopy. (A) Schema of TH-302 redox cycling under normoxia and fragmentation under hypoxia. (B) Spin trapping of superoxide by DMPO (110 mM) and the EPR spectra under normoxia or hypoxia. The spin adduct signal [DMPO−O2−•] is indicated by downward arrows. Experimental condition; DPBS-10% DMSO containing 1 mM NADPH, 4.5 μg/ml POR, and 1 mM of TH-302. (C) EPR spectra recorded under the indicated oxygen concentration. The spin adduct signal [DMPO−O2−•] formed by PORs during the reduction of TH-302 at 37°C is shown by downward arrows. DMPO-CH3 is indicated by (*). (D) A plot of [DMPO−O2−•] signal (every 1 min) recorded for 15 min under the indicated condition of enzymatic reaction at 37°C. (E) A plot for the maximum intensity of [DMPO−O2−•] (open circles) and the proportion of decline of [DMPO−O2−•] (closed circles) at time point of 10 min in Figure 1D. DMPO, dimethylpyrroline N-oxide; DMSO, dimethyl sulfoxide; DPBS, Dulbecco's phosphate-buffered saline; EPR, electron paramagnetic resonance; POR, NADPH cytochrome P450 oxidoreductase.