Reconstitution of Photosynthetic Energy Conservation

Abstract

A preparation of reaction centers of photosystem I from spinach chloroplasts was incorporated into lipid vesicles by sonication. Incorporation was tested by Sepharose-4B chromatography and by comparison of elution profiles of photosystem-I reaction center liposomes and free reaction centers. In the presence of reduced N-methylphenazonium methosulfate the reaction center liposomes catalyzed net proton extrusion in the light but at the same time showed light-induced quenching of 9-aminoacridine fluorescence with similar extent and kinetics known for chloroplasts. Two vesicle populations were apparently present: 1 right side-out and 1 inside-out with respect to orientation of the incorporated reaction center complex. Net proton movements were influenced by the nature of cations present in the suspending medium. Possibilities for effects of surface charge on these movements were discussed.