Tethered proteins speed up photosynthetic electron transfer. Few renewable-energy technologies can match the simplicity of the natural photosynthetic reaction in which water in chlorophyll-imbued plants and simple organisms is converted into O2 and the fuel source H2. In cyanobacteria, a chlorophyll-containing organism, proteins shuttle electrons that drive the production of H2 through the reduction of H+; however, the process is limited by the diffusion. Now, researchers at the Pennsylvania State University and Ruhr University Bochum in Germany have devised a faster system in the lab. As shown in the image, the photosystem reaction center (PS I; green)—a photon-absorbing complex found in cyanobacteria—is cross-linked to CytC6, an electron-transfer protein. That hybrid molecule is then tethered to HydA—the proton-reducing catalyst—by a synthesized hydrocarbon chain (jagged red line) that acts like a molecular wire and allows electrons to tunnel through. Thus the system achieves an...

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