Intermolecular coupling reactions, transient

Fig. 1. The three different interaction ranges ofEPR spectroscopy are shown on a transient semiquinone anion radical QX of a bacterial reaction centre of Rhodobacter sphaeroides (R26). The structural data for ttiis illustration are taken from the X-ray structure of Ermler et al. [2]. Upper left The local interactions such as intermolecular hyperfine couplings and g-tensor of the ubisemiquinone-10 anion radical characterized by multifrequency-EPR. Upper right The local protein surrounding (within a distance of 0.6 nm to the semiquinone rachcal) as observable by ENDOR and ESEEM spectroscopies. Lower picture The interaction of the semiquinone anion radical with the other transient paramagnetic centres in the protein complex as observable with pulse-EPR methods.

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