Studies of the protein binding pocket for naphthoquinones in type I (ferredoxin-reducing) reaction centres.

We have demonstrated [1] that photoaccumulation under reducing conditions at 205K produces an electron paramagnetic resonance (EPR) signal arising from a stable semiquinone form of the phylloquinone electron acceptor (A1•−) in Photosystem I (PSI) preparations. Electron Nuclear Double Resonance (ENDOR) studies of the phyllosemiquinone [2] have detected hyperfine couplings arising from protons, and thus given information on the electronic structure of the phyllosemiquinone in PSI.