Structural implications of transient X-, K- and W-band EPR spectra of deuterated and protonated reaction centers of Rhodobacter sphaeroides R-26

We have reexamined the X-ray structural implications of reaction center proteins (bRCs) of Rhodobacter sphaeroides R-26 by simultaneous least-squares fitting of six different transient EPR spectra at three frequencies (X-, K- and W-band) for both deuterated and protonated bRCs. Several possible g-tensor orientations from X-ray structure are found to produce similar spectral features by a small change in the g factor. We have obtained the fitted principal g values that are slightly different from a previous report. No exchange coupling J between P+ and Q− is needed for the fit.