Photosystem I Photopolymerizes Pyrrole into Spherical Nanocomposites

Conductive polymers have been shown to be an effective scaffold for proteins when designing bioelectrochemical systems, particularly for the Photosystem I protein. Utilization of synthetic polymer chemistry has allowed a great deal of tunability within the protein/polymer interface to improve electron transfer from the proteins, ultimately progressing toward direct electron transfer from the active sites. Seeking to address this issue, a new heterogeneous approach is presented to synthesize Photosystem I/polypyrrole (PSI/PPy) composites. The oxidative potential of PSI's P₇₀₀ reaction site was leveraged to polymerize pyrrole into a molecular wire, providing a more efficient means of electron transfer to the protein. Over the course of several hours of photopolymerization of Py in a PSI film, PPy not only wired PSI but began incasing the protein within conductive polymer nanoparticles. These resulting composite nanoparticles were extensively characterized by electron microscopy and electrochemical techniques to showcase their synergistic properties.