Protein-driven energy transduction across polymeric biomembranes

Abstract

Block copolymer-based membrane technology enables the development of a versatile classof 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 ofexisting 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 asNafion® in order to improvethe ability of Nafion® to retain leaking protons. Also, the demonstration of protein-driven current productionacross these membranes represents a possible alternative power source that is both highlyefficient and light in weight. Our work has demonstrated the fabrication of large-areacopolymer biomembranes that are functionalized by bacteriorhodopsin (BR) andcytochrome c oxidase (COX) ion transport proteins. Among their many advantagesover conventional lipid-based membrane systems, block copolymers can mimicnatural cell biomembrane environments in a single chain, enabling large-areamembrane fabrication using methods such as Langmuir–Blodgett (LB) deposition.Following the large-scale insertion of proteins into block copolymer LB films, we havedemonstrated significant pH changes based upon light-actuated proton pumping.Protein activity across the BR and COX-functionalized membrane has also beenobserved using impedance spectroscopy as well as direct current measurement.