FIG. 3.

Room temperature continuous wave electron paramagnetic resonance spectra (cw EPR) for HbpS-G71R1 (left panel) and HbpS-S139R1 (right panel) in native (unstressed) form (black) and after iron-mediated oxidative stress (gray). Original spectra contained a significant amount of contributions of unbound spin label due to the corresponding sample preparation/labeling procedure (described in Materials and Methods section) that have been largely removed by subtraction of correspondingly scaled spectra of free SL in buffer solution. Artifacts caused by this procedure are marked with an asterisk. The inset shows the low field area of the spectra for HbpS-G71R1.