Mimicking bacterial photosynthesis

Photosynthesis in bacteria involves absorption of light by antenna chromophores and transfer of excitation to reaction centers, which convert the excitation energy to electrochemical potential energy in the form of transmembrane charge separation. A proton pump uses this stored energy to generate proton motive force across the membrane, which in turn is used to synthesize adenosine triphosphate (ATP). All of these steps can now be mimicked in the laboratory. Artificial antennas and reaction centers can be prepared from chromophores, electron donors and electron acceptors linked by covalent bonds. The artificial reaction centers can be inserted into the lipid bilayers of liposomes, where they act as constituents of transmembrane light-driven proton pumps. Finally, the proton gradient thus produced can be used to synthesize ATP via catalysis by FoFl-ATP synthase isolated from chloroplasts. The synthetic and natural systems can use light energy to produce ATP at comparable chemical potentials.