Semiquinone radical anions in plant photosystem II

Approximate mode descriptions, experimentally measured vibrational frequencies(cm )(SO) of decyl-PQ and decyl-PQ , and scaled calculated harmonic vibrational frequencies(cm ) for selected modes of plastoquinone-1 and plastosemiquinone-1 anion each contacted by two water molecules.(50) Calculations were done with the B3LYP/6-3 lG(d) method. 

Even where structures of quinone-protein complexes are available from X-ray diffraction experiments, the structures, side-chain conformations, and intermolecular contacts with proteins for the corresponding quinoidal radicals must usually be inferred indirectly from spectroscopic data. The primary spectroscopic methods used to infer structures of quinoidal radicals in photosynthetic reaction center proteins are designed to probe molecular vibrations and spin properties. Directly measurable quantities that are also 

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