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 (A(1)), and more than 90% of the Chi mere removed to yield the PSI complex with 9-11 molecules of Chi per reaction-center unit. The complexes retained the primary electron donor and acceptor (P700 and A(o)), in addition to three FeS clusters (F-X, F-A and F-B), 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 A(o) and A(1), (3) the energy-gap dependency of the reaction rate between A(o) and the artificial quinones reconstituted at the A(1) site, (4) the direct excitation of P700 followed by the ultra-fast electron transfer from P700 to A(o), and (5) the de- and re-stabilization of the PSI structure by the removal and reconstitution, respectively, of antenna Chi in the presence of certain lipids.