plastosemiquinone

— Also, DFT calculations on the plastosemiquinone anion radical in PSII found the histidine N δ to be the stronger of the two H-bond donors. 47 Therefore, the previous assignments of the hydrogen bond proton couplings for SQ A in PSII are not unambiguous. 46 From a comparative analysis of available nqi data for several semiquinone species and for copper complexes, 17 we find that the protonated imidazole nitrogens of these systems share similar valence orbital occupancies.