Selective Extraction of Antenna Chlorophylls, Carotenoids and Quinones from Photosystem I Reaction Center

By the ether treatment of lyophilized PSI pigment–protein complexes, all the carotenoids and the secondary acceptor phylloquinone (A1), and more than 90% of the Chl were removed to yield the PSI complex with 9–11 molecules of Chl per reaction-center unit. The complexes retained the primary electron donor and acceptor (P700 and A0), in addition to three FeS clusters (FX, FA and FB), and showed an activity of highly efficient electron transfer when phylloquinone was reconstituted. The methods for the preparation and the characterization of the ether-extracted PSI complexes are reviewed in this article. We also review the studies done with this PSI preparation on (1) the identification of the absorption and fluorescence spectra of P700, (2) the nano- and picosecond reaction of A0 and A1, (3) the energy-gap dependency of the reaction rate between A0 and the artificial quinones reconstituted at the A1 site, (4) the direct excitation of P700 followed by the ultra-fast electron transfer from P700 to A0, and (5) the de- and re-stabilization of the PSI structure by the removal and reconstitution, respectively, of antenna Chl in the presence of certain lipids.