FIG 9.

Detection of ^·OH radicals in pneumococci by 4-POBN and DETAPAC-ethanol spin trapping. Shown are the EPR spectra of 4-POBN spin trapping in wild-type and double-mutant samples and, for comparison, a medium-only sample. The unassigned signal near the free-electron g value of 2.0023 (333.0 mT) was deleted. The EPR conditions were as follows: microwave frequency, 9.346 GHz; microwave power, 10 mW; modulation amplitude, 0.2 mT; modulation frequency, 100 kHz; temperature, 295 K. The spectra of wild-type and double-mutant samples represent an average of 96 scans minus the bacterial-medium spectrum. The bacterial-medium spectrum represents an average of 224 scans, with polynomial baseline correction. The spectra were baseline corrected using a polynomial function.