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(R) in order to improve the ability of Nafion(R) 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.