Langmuir-Blodgett Monolayer Films of the Rhodopseudomonas Viridis Reaction Center: Determination of the Order of the Hemes in the Cytochrome C Subunit

The Langmuir-Blodgett (LB) film technique has been applied to produce oriented and photo-active films of isolated reaction center cytochrome c complexes (RC-cyt c) and chromatophore membranes from the photosynthetic bacterium Rhodopseudomonas viridis. Linear dichroism (LD) and redox potentiometry have been used to identify the four cytochrome c hemes of the RC-cyt c complex. Resolved angular orientations of the four hemes in LB films of both isolated RC-cyt-c complexes and of chromatophore membranes permit the reduction of the 24 possible arrangements to two. Additional structural and functional information from other sources allows us to propose a model which best accounts for all the available experimental data.