Protein-driven energy transduction across polymeric biomembranes

Block copolymer-based membrane technology enables the development of a versatile class of nanoscale materials in which biomolecules, such as membrane proteins, can be reconstituted. These active materials possess a broad applicability in areas such as the enhancement of existing technologies or production of current-generating films for power sources. For example, these active materials can be integrated with fuel cell ion transport membranes such as Nafion® in order to improve the ability of Nafion® to retain leaking protons. Also, the demonstration of protein-driven current production across these membranes represents a possible alternative power source that is both highly efficient and light in weight. Our work has demonstrated the fabrication of large-area copolymer biomembranes that are functionalized by bacteriorhodopsin (BR) and cytochrome c oxidase (COX) ion transport proteins. Among their many advantages over conventional lipid-based membrane systems, block copolymers can mimic natural cell biomembrane environments in a single chain, enabling large-area membrane fabrication using methods such as Langmuir–Blodgett (LB) deposition. Following the large-scale insertion of proteins into block copolymer LB films, we have demonstrated significant pH changes based upon light-actuated proton pumping. Protein activity across the BR and COX-functionalized membrane has also been observed using impedance spectroscopy as well as direct current measurement.